Categories
Horses

Inflammation Of The Lower Airways

Evidence indicates that lower airway inflammation is prevalent in the horse. This relates to stable, arena, and paddock conditions that put the horse at risk, in addition to constant challenges with viruses and bacteria. Exercise may increase lower airway inflammation, but evidence for this is scant in the equine species. Little information exists regarding the nature of inflammation in inflammatory airway disease. By association, studies in horses with heaves have demonstrated the presence of allergic phenomena (increased cytokines IL-4, IL-5 and reduced interferon gamma, increased mast cells and neutrophils, reduced antiproteases, increased procoagulants, histamine, leukotrienes, metalloproteinases, and other inflammatory mediators). In early studies many horses with “chronic obstructive pulmonary disease” (pre-heaves) had increased viral (influenza) antigen in their tracheal mucus. Furthermore, influenza infection caused prolonged inflammation and airway hyperreactivity similar to the inflammation observed in some horses with inflammatory airway disease.

Other studies have shown that exercise-induced pulmonary hemorrhage causes transient neutrophilic inflammation. Thus far, two studies have shown a lack of association between EIPH, airway inflammation, and lung dysfunction. Evidence exists of a genetic basis for heaves in families of horses, but the basis for this tendency has not been discovered. Some researchers also have found mechanical dysfunction in horses with inflammatory airway disease that might suggest a congenital tendency towards bronchoconstriction, but the structural basis for this finding is unknown. Endotoxin derived from stable manure also has been implicated as a cause of inflammation in the airways. In conclusion, the pathogenetic basis of the inflammation is unknown, but it is surely multifactorial.

Inflammation can be characterized using transtracheal aspiration (TTA) or bronchoalveolar lavage (bronchoalveolar lavage; see “Tracheal Aspirates: Indications, Technique, and Interpretation” and “Bronchoalveolar Lavage” for a description of the techniques). The transtracheal aspiration samples the central airways (a collection of all secretions) and the bronchoalveolar lavage a more peripheral segment of lung. Large surveys of poor performance racehorses using bronchoalveolar lavage cytology have revealed abnormalities in cytology such as increased neutrophils, mast cells, lymphocytes, or eosinophils, that distinguish the horses with inflammatory airway disease from controls. Despite the large numbers of inflammatory cells in bronchoalveolar lavage, these samples reveal no evidence of infection. In later studies, bronchoalveolar lavage inflammation was associated with pulmonary dysfunction in both racehorses and non-racehorses. Multiple studies in sport horses with exercise intolerance found that an increase in bronchoalveolar lavage mast cells or neutrophils is associated with abnormal lung function, that is, small airway obstruction, expiratory flow limitation, and/or airway hyperreactivity (i.e., the tendency to bronchoconstrict). In particular, horses with exercise limitations and airway hyperreactivity, in comparison with control horses, had an elevation of mast cells and leukotrienes. These studies confirm that some horses with inflammatory airway disease have a marked functional disturbance that limits performance. The mast cell may play a pivotal role in releasing inflammatory mediators that cause bronchoconstriction and mucus production and act as growth factors to increase airway wall thickening. Although the evidence is strong that this is an allergic type phenomenon, insufficient proof exists to substantiate the use of the phrase “allergic airway disease.”

In exercise studies using metabolic stress tests on the treadmill to determine aerobic capacity (Vo2max), poor performance often is related to lower airway disease, detected by neutrophilic inflammation on transtracheal aspiration in many cases. From these large studies, researchers concluded that bronchitis or bronchiolitis play a significant role in exercise intolerance, although no direct statistical link is made between the degree of inflammation and Vo2max. Further studies are warranted to understand the link between inflammation and reduced exercise tolerance.

Categories
Horses

Medical Therapy For Upper Airway Disease

Because of the possibility that regional inflammation of the upper airway may be responsible for some obstructive upper airway diseases, enteral, parenteral, and topical antiinflammatory therapy may prove useful in their treatment. Although a proven correlation between airway inflammation and upper airway obstructive diseases remains to be established, an association exists between the presence of upper airway inflammation and the occurrence of obstructive upper airway disease. This premise finds support in numerous anecdotal accounts of improved upper airway function in horses after antiinflammatory treatment.

Systemic and inhaled corticosteroids have been used successfully to treat upper airway inflammation and neuromuscular dysfunction that results in dorsal and lateral nasopharyngeal collapse and dorsal displacement of the soft palate. After a thorough physical examination and complete blood cell count and fibrinogen have been performed to rule out active bacterial infection, systemic corticosteroid therapy can be initiated. Dexamethasone can be administered in a tapering dose, orally, at 0.02 to 0.04 mg/kg twice daily for 10 days to 2 weeks, followed by 0.02 to 0.04 mg/kg, once daily for 10 days to 2 weeks, then 0.02 to 0.04 mg/kg every other day for 2 weeks. The horse should be rested during this time, and either turned out in a pasture or worked lightly for 6 to 8 weeks. The airway inflammation typically resolves within 7 to 10 days, however, upper airway function may not improve for as long as 4 months, thus patience is important. Oral prednisolone can also be given at 1 to 2 mg/kg with the same dosing regimen as dexamethasone. It is important to note that oral prednisone therapy in horses is ineffective. Prednisone is poorly absorbed by the equine gastrointestinal tract and is not converted to the active antiinflammatory form, prednisolone.

Inhaled and topical medications have also been used to decrease airway inflammation in horses. Dexamethasone and prednisolone can be nebulized for distribution in the nasopharynx. Antiinflammatory topical throat sprays, composed of nitrofurazone, dimethyl sulfoxide, glycerin, and prednisolone or dexamethasone, can be administered into the nasopharynx by passing a uterine infusion pipette or narrowing tubing of sufficient length into the nasopharynx and spraying 10 to 20 ml of the solution into the nasopharynx. Application of throat spray may be performed twice daily for 2 weeks and then daily for 2 weeks.

Interferons are a family of proteins that have antiviral and immunomodulatory activity. Oral administration of a low dose (0.1 IU/kg) of human interferon-α (HuIFNα) reduces tracheal and nasopharyngeal exudate in racehorses with inflammatory airway disease. Horses are generally treated daily for 5 to 7 days. Oral administration of HuIFNα likely is effective because it stimulates lymphoid tissue in the oropharynx. At Michigan State University the following procedure is used to prepare interferon:

1. Add 1 ml of interferon α-2a (3 million U/ml, Roferon-A) to 99 ml of 0.9% saline and mix well but do not shake. This makes 100 ml of 30,000 U/ml interferon α-2a.

2. Remove 143 ml of 0.9% saline from a 1-L container and add 3 ml of the 30,000 U/ml interferon α-2a solution. The final volume of 900 ml will contain 100 U/ml interferon α-2a.

3. Divide the 100 U/ml solution into aliquots of 30 ml each, place in 1 oz bottles, and refrigerate.

4. Label each aliquot with the following information:

  • • Interferon α-2a 100 U/ml.
  • • Store in refrigerator.
  • • Prepared on date _____.
  • • Discard after 30 days.

Discard any solution remaining from step 1. Interferon tends to bind to surfaces and any long-term storage must be in a – 70° C freezer.

Categories
Horses

Anemia Secondary to Inadequate Erythropoiesis

The average lifespan of the equine erythrocyte is 150 days. Therefore anemia caused by inadequate erythropoiesis is an insidious process associated with scant, nonspecific clinical signs. Causes include anemia of chronic disease, nutritional deficiency, bone marrow aplasia, or myelophthisic disease. Of these, anemia of chronic disease () associated with infectious, inflammatory, or neoplastic disorders is most commonly encountered in horses.

Anemia Of Chronic Disease

anemia of chronic disease is well-recognized in mammalian species. Three mechanisms have been incriminated in the disease process: shortened erythrocyte life span, insufficient bone marrow response to demand for red blood cells, and decreased release of iron from the reticuloendothelial system. Accelerated red cell destruction may be the result of activation of the mononuclear phagocyte system in response to inflammation. Also, the intravascular response to inflammation may cause increased erythrocyte damage during passage through small vessels with subsequent removal by the reticuloendothelial system. Normally, the bone marrow would respond to such increased consumption with an appropriate increase in red blood cell production. The rate-limiting factor in the marrow’s failure to respond to anemia of chronic disease may be inadequate erythropoietin production. Erythropoietin is the hormone primarily responsible for regulation of erythropoiesis in the bone marrow. Although erythropoietin production is increased in people and in animal models of anemia of chronic disease, the hormone is deficient relative to the anemia. Administration of pharmacologic doses of recombinant erythropoietin will reverse anemia of chronic disease. In addition to the relative erythropoietin deficiency, erythroid progenitor cell activity is inhibited in anemia of chronic disease, as is iron release from the reticuloendothelial system. It appears likely that the abnormal bone marrow and iron metabolism responses in anemia of chronic disease are mediated by cytokines produced in response to inflammatory conditions, including infection and neoplasia. Interleukin-1, tumor necrosis factor, and 7-interferon all have been shown experimentally to play roles in anemia of chronic disease.

Diagnosis, Clinical Signs, and Treatment

anemia of chronic disease is diagnosed by the presence of a chronic disease process accompanied by a mild to moderate, nonregenerative, normochromic, and normocytic anemia. Serum iron and total iron-binding capacity are decreased, but normal to increased iron stores can be demonstrated by normal serum ferritin concentration or positive Prussian blue stain for marrow iron.

The clinical signs of anemia of chronic disease are those related to the primary disease, and treatment is solely related to eliminating the underlying disease condition and to ensuring that the anemia is not caused by blood loss or hemolysis. Diseases associated with anemia of chronic disease in horses include pleuropneumonia, internal abscessation, peritonitis, chronic organ failure, immunemediated or granulomatous diseases, neoplasia, and chronic viral disease such as equine infectious anemia. Although hypoferremic, horses with anemia of chronic disease have normal iron stores and do not require iron supplementation.

Nutritional Deficiency

Inadequate erythropoiesis caused by dietary inadequacy is rare in horses. Vitamin B12 and folic acid are important co-factors in erythrocyte maturation. In horses, gastrointestinal bacteria synthesize vitamin B12, thus eliminating the need for exogenous consumption. Absorption deficiency, as seen in pernicious anemia in people, is not recognized. Deficiencies in other micronutrients involved in erythrocyte production — such as copper, cobalt, and iron — are rare. Iron-deficiency anemia in horses is almost invariably the result of chronic blood loss. Iron-deficiency anemia is diagnosed on the basis of hypoferritinemia, hypoferremia, normal to increased total iron binding capacity, and detection of decreased iron stores on examination of bone marrow aspirate. In horses, normal serum ferritin has been reported as 152 ± 54.6 ng/ml, normal iron concentration as 120 ± 5.0 μg/dl, and normal total iron binding capacity as 388 ± 8.1 μg/dl.

Iron metabolism changes rapidly in foals. Serum iron concentration is very high in the first few days of life; under no circumstances should oral or parenteral iron supplementation be given during this period. Thereafter, some controversy regarding the presence of a functional iron deficient state in the first 4 to 6 weeks of life exists because of the high iron demands associated with rapid growth and a milk diet that is relatively poor in iron. Recently, iron deficiency was reported in a group of stabled Dutch warmblood foals that were housed indoors and fed freshly cut grass. These foals were listless compared to control foals on pasture. In addition, stabled foals had significantly lower hemoglobin concentrations, packed cell volumes, blood iron concentrations, and saturation total iron binding capacities. Laboratory values and attitude scores improved in stabled foals after oral iron supplementation.

Anemia Due To Bone Marrow Aplasia Or Myelopthisis

Categories
Horses

Treatment of Pastern Dermatitis

The appropriate therapy obviously involves identification of the predisposing, perpetuating, and primary factors. In general, avoiding pastures/paddocks with mud, water, or sand may minimize predisposing factors. Keeping patients stalled during wet weather and until morning dew has dried is often rewarding. Use of alternate sources of bedding may be beneficial because the chemicals in treated or aromatic types of wood shavings may result in contact dermatitis. Lastly, clip hairs — especially feathers — to avoid moisture retention.

Perpetuating factors should be addressed according to the severity of the condition. The most conservative approach includes cleansing lesions with antimicrobial shampoos (benzoyl peroxides, chlorhexidine, ethyl lactate, imidazoles) twice daily for 7 to 10 days and then tapering in frequency. If a dry environment is not possible, the affected pastern areas can be protected with ointments (creating a moisture barrier); with padded and water-repellent bandages (changed q24-48h); or with Facilitator, a hydroxy-ethylated amylopectin liquid bandage that is replenished every 1 to 3 days. If the lesions are exudative, astringent solutions — such as lime sulfur (LymDyp), aluminum acetate solutions, black tea bag or sauerkraut poultices, or acetic acid/boric acid wipes (Malacetic Wipes, Dermapet Inc., West Plains, Mo.) — should be used after cleansing.

Topical sprays, creams, or ointments that contain antibiotics, steroids, antifungal agents, or a combination thereof may benefit the patient, depending on the diagnosis. A 2% mupirocin ointment (Bactoderm), with excellent tissue penetration, is the author’s preference for addressing localized dermatophilosis and bacterial dermatitis. A DMSO / thiabendazole / sulfa ointment has also been described in the fourth edition of Current Therapy in Equine Medicine. If generalized to all four limbs, treatment of the bacterial dermatitis is best accomplished with daily systemic antibiotics (trimethoprim/sulfa 30 mg/kg/day or cephalexin 22 mg/kg q8hrs) until 7 days after clinical resolution.

Lime sulfur dips and chlorhexidine / imidazole-containing shampoos, sprays, and residual leave-on products comprise the current antifungal arsenal in veterinary medicine. Topical enilconazole (Imaverol), labeled for use in horses in various countries other than the United States, has been used to treat fungal infections with reported success. Many veterinary dermatologists feel that systemic griseofulvin lacks efficacy for the treatment of equine dermatophytosis.

Ectoparasiticidal therapy consists of avermectins, topical organophosphates (malathion, coumaphos), pyrethroids (permethrin, flumethrin), lime sulfur, and fipronil (Frontline). The latter has had recent success in the treatment of Chorioptes bovis within a group of heavier cob and draught-cross horses. Of note was the ability of the parasite to survive off the host, enduring solely in the presence of skin debris in a moist and dark environment and thus emphasizing the need for environmental management to prevent recurrence.

Immunomodulators have been used for the condition. Interferon-a2a given at 1000 IU/ml on a cycle of 1.0 ml per horse daily for 3 weeks and then off for 1 week has been used by the author to help stimulate the local immune defense system, with very little cost or side effects. Immune-mediated conditions such as PLV, however, require a significant immunosuppressive effort to achieve resolution and control of the clinical signs. High-dose glucocorticoids, preferably dexamethasone (0.1-0.2 mg/kg q24h for 7-14 days, then taper over the next 4-6 weeks), along with reduction of UV light exposure by stabling or covering with a light bandage, appears to control — if not resolve-many cases. Should resolution of clinical signs not be achieved by 14 days, the author has achieved excellent results by adding pentoxifylline (PTX), a phosphodiesterase inhibitor. PTX has been reported to have multiple immunomodulatory effects that potentiate the effectiveness of traditional immunosuppressive drugs (i.e., steroid-sparing effect). These include inhibition of lymphocyte activation and proliferation; increased lymphocyte suppression; suppression of tumor necrosis factor (TNF)-a, lymphotoxin, and interferon-7 production; and upregulation of IL-10 mRNA that leads to increased IL-10 serum levels. Oral absorption varies considerably between individuals; thus reported dosages range between 4 to 8 mg/kg every 12 hours.

Once the skin has returned to normal, long-term control of PLV may be achieved by a combination of topical steroids (betamethasone valerate 0.1%, aclometasone 0.05%), coupled with an every other day systemic regimen of PTX and, if necessary, low-dose dexamethasone on an alternate day basis.

The prognosis and healing time of equine pastern dermatitis depends on the stage of disease when treatment begins and on the ability to identify the etiology. Ensuring that predisposing, primary, and perpetuating factors are encompassed in a diagnostic and treatment plan will optimize the likelihood of a positive outcome.

Categories
Horses

Atopy

Atopy is a genetic, dermatologic, and/or respiratory condition that occurs when a horse develops sensitizing antibodies to environmental allergens such as molds, grasses, trees, weeds, fabrics, and dust. The sensitizing antibody that is produced, immunoglobulin E (IgE), causes cross-linkage on mast cells within the affected tissue. This cross-linkage results in the release of inflammatory mediators such as leukotrienes and prostaglandins. The end result is inflammation of the skin and/or respiratory system and discomfort for the affected horse.

Arabian and Thoroughbred horses appear to be predisposed to developing atopy. This rinding supports the idea that atopy is an inherited condition in horses; however, the exact mode of inheritance remains unknown. One stallion has been documented to have atopy and sire five offspring with atopy, and in each breeding the mare was different. This finding suggests the possibility of a dominant inherited trait for equine atopy. More studies need to be performed to prove or disprove this theory.

Not all horses with atopy have allergies to the same allergens. It is therefore important to have some method by which offending allergens are identified so that they can be prevented and/or the horse can be managed through hyposensitization treatment. Over the years, intradermal allergy testing and serum allergy testing have been developed and used to identify potential offending allergens. As with any test, false-positive and false-negative reactions can occur and can make interpretation difficult. The clinician must be familiar with the limitations and advantages of each test. Interpretation requires that the veterinarian correlate the history with clinical signs and pollination times of the various allergens. Once the veterinarian has this information, a proper recommendation for treatment may be made.

Atopy: History

Most horses with atopy have a seasonal skin and/or respiratory problem. Reports of horses with nonseasonal problems exist, but this occurrence is atypical. When a non-seasonal history exists, the horse usually has an allergy to molds or dust. Mold allergies usually cause clinical signs throughout the year but tend to be worse in the spring and fall.

Horses with atopic dermatitis usually have a history of pruritus, but an owner who does not spend a lot of time with the horse may miss this sign. Some horses with urticaria also may not be pruritic. Therefore the history of pruritus is not always helpful in the determination of whether an urticarial horse is atopic.

The clinical signs for equine atopy usually develop at a young age — 1 ½ to 4 years old. It is important to remember that movement of the horse may play an important role in determining the age at which atopy develops. A horse that has lived 5 or more years in one geographic area without atopy may develop signs after moving to a different geographic area.

Clinical Signs

A variety of clinical signs reportedly have been associated with equine atopy. The most common sign is pruritic dermatitis. The lesions include excoriations, alopecia, licheni-fication, and hyperpigmentation. Primary skin lesions (papules, pustules) rarely occur. As previously described, some horses have chronic recurrent urticaria that may or may not be pruritic. The dermatologic lesions are usually found on the face, ear, venrrum, and legs. Some horses with atopy look similar to horses with insect hypersensitivity.

Horses with heaves and atopy may have clinical signs that are no different than those in horses with heaves not associated with atopy. These signs can include head-tossing, snorting, coughing (especially dry, unproductive coughs), bilateral mucopurulent discharge in the nostrils, runny eyes, stomping, rubbing the nose and eye on the front leg or on an object in the environment, labored breathing, and exercise intolerance.

Differential Diagnoses

Differential diagnoses for pruritic atopic dermatitis include insect hypersensitivity, food allergies, and contact hypersensitivity. Insect hypersensitivity is the most common. Differential diagnoses for horses with respiratory problems include upper respiratory infection (viral, bacterial, fungal), congestive heart failure, and bronchitis.

Atopy: Diagnostic Tests

Atopy: Treatment

Atopic Dermatitis

Corticosteroids, antihistamines, and essential fatty acids are the three main groups of drugs used for antipruritic treatment in the atopic horse. Prednisolone can be administered at 0.5 to 1.5 mg/kg every 24 hours for 4 to 14 days, depending on the severity of the problem. This treatment is followed by a maintenance dose of 0.2 to 0.5 mg/kg every 48 hours. Alternatively, either oral or injectable dexamethasone may be used. The initial dose of dexamethasone is 0.01 to 0.02 mg/kg every 24 hours for 4 to 7 days, followed by a maintenance dose of .01 to .02 mg/kg every 48 hours. Side effects associated with steroid use include polyuria, polydipsia, increased susceptibility to infection, mood changes, elevations in liver enzymes, and laminitis. The major predisposing factor for development of laminitis is a previous history of laminitis or predisposing hoof conformation, such as small feet on a large horse.

Antihistamines competitively inhibit the histamine Hi receptor on the cell surface and thereby prevent the action of histamine on the cell. Antihistamines do not inactivate histamine or prevent its release. Several different antihistamines are available. Hydroxyzine hydrochloride is the first choice of most veterinary dermatologists. The dose ranges from 200 mg to 400 mg every 24 hours (PO or IM) to 1.5 mg/kg every 8 to 12 hours. This author’s second-choice antihistamine is chlorpheniramine maleate (200 mg ql2h PO regardless of body weight). Doses of 0.25 mg/kg every 12 hours have also been reported to be successful. Two other antihistamines that have been reported as effective are diphenhydramine hydrochloride (0.75 to 1 mg/kg ql2h PO) and pyrilamine maleate (1 mg/kg ql2h IV). Doxepin hydrochloride, a tricyclic antidepressant with antihistaminic properties, has also been used in horses at a dose of 300 to 400 mg every 12 hours or 0.5 to 0.75 mg/kg every 12 hours with varied success.

Side effects associated with antihistamine administration include sedation or behavior changes. The drug withdrawal period recommended by the American Quarter Horse Association for antihistamines is 10 days before the sporting event.

Essential fatty acids shift the arachidonic acid cascade away from production of proinflammatory mediators. This author has had the best experience with Derm Caps (DVM Pharmaceuticals, Miami, Fla.). The dose of Derm Caps ES for the average-sized horse is 5 capsules every 12 hours, whereas the dose for Derm Caps 100 is two to three capsules every 12 hours. As with any fatty acid, loose stools are a potential complication of this medication. If the horse develops loose stools after taking fatty acids, the next dose should be omitted and subsequent doses reduced by one capsule to see whether the horse tolerates the new dose. Hydroxyzine may be more effective when combined with the fatty acid treatment because fatty acids and antihistamines have a synergistic effect on pruritus in small animals. Derm Caps have two problems — cost and the capsule form. Most owners open the fatty acid capsule and sprinkle the contents on the grain. For most horses, palatability does not appear to be a problem.

Topical products may also relieve pruritus. Some ingredients that appear to be especially useful in horses are oatmeal, pramoxine, and hydrocortisone. Various combinations of these three ingredients are available commercially.

Hyposensitization therapy desensitizes the horse to allergens that are suspected of causing the allergic signs. The exact mechanism of action is unknown, but the current thought is that allergy vaccines stimulate Th1 cells to produce and release interferon (IFN)-γ. This IFN-γ blocks the stimulation of IgE antibody synthesis by IL-4 from Th2 cells. Reported response to therapy varies from 60% to 80%, which is similar to reports in other species of animals. The side effects of hyposensitization therapy are minimal. Some animals develop swelling at the injection site, especially when the injection administered is the more concentrated allergen solutions. Anaphylaxis is rare. Different allergy companies and different dermatologists use different vaccines schedules, which may explain some of the variability in response to the hyposensitization therapy. The usual vaccine maintenance schedule is 1 ml of a 20,000 protein unt (PNU) per ml of aqueous suspension of allergen administered every 7 to 21 days. The frequency of the vaccine administration depends on the horse’s response to therapy.

Prognosis

Because equine atopy is an inherited condition, horses with this problem will have atopy for the rest of their lives. The owners of these horses need to be made aware that the horse will never be “cured.” Instead, the owners must commit to treating and managing their horses’ allergies on a long-term basis. The owners need to be aware of this situation before any treatment is instituted. With proper management, most horses can lead happy and productive lives.

Categories
Veterinary Medicines

CaniLeish for Dogs

Scientific discussion

This medicine is approved for use in the European Union

CaniLeish is a lyophilisate and solvent for suspension for injection, intended for the active immunisation of Leishmania negative dogs from 6 months of age to reduce the risk to develop an active infection and clinical disease after contact with Leishmania infantum.

The active substance of CaniLeish is Leishmania infantum excreted secreted proteins (ESP).

CaniLeish was eligible for the submission of a dossier for granting of a Community marketing authorisation via the centralised procedure under Article 3 (2) (a) of Regulation (EC) No 726/2004 which refers to medicinal products intended for use in animals containing a new active substance which was not authorised in the Community. The Committee also confirmed that the requirements for veterinary products intended for Minor Use or Minor Markets (MUMS) were met and therefore the provisions of the relevant guideline were applicable for this application.

No specific inspection was considered necessary with regard to CaniLeish. The presented pharmacovigilance system was considered satisfactory.

The benefits of CaniLeish are the stimulation of active immunity in Leishmania negative dogs from 6 months of age to reduce the risk to develop an active infection and clinical disease after contact with Leishmania infantum. The onset of immunity is 4 weeks after the primary vaccination course and the duration of immunity is 1 year after the last (re-)vaccination.

The most common side effects are moderate and transient local reactions that may occur after injection such as swelling, nodule, pain on palpation or erythema. These reactions resolve spontaneously within 2 to 15 days. Other transient signs commonly seen following vaccination may be observed such as hyperthermia, apathy and digestive disorders lasting 1 to 6 days. Allergic-type reactions are uncommon and appropriate symptomatic treatment should then be administered.

Canine leishmaniosis is a widespread infectious disease in endemic areas of the Mediterranean basin, Asia and America. This is a zoonosis considered as a serious veterinary problem with an increasing impact on public health. The disease is due to the development and multiplication in the macrophages and mononuclear cells of a protozoan parasite – Leishmania infantum. The infected dogs constitute the main domestic reservoir and play a central role in the accidental transmission of parasites to humans. The parasite is transmitted from an infected dog to a non-infected dog by the bites of sandflies of the genus Phlebotomus. The outcome of the infection is highly variable. Infected dogs may develop symptomatic infection resulting in death if not treated or develop only one or many mild symptoms but a high percentage of infected animals remain asymptomatic.

List of main abbreviations used frequently through the scientific discussion

BSA: Bovine Serum Albumin

Cv: coefficient pf variation (validation of methods)

CMLA: canine macrophage leishmanicidal activity

Con A: Concanavalin A

DTH: Delayed Type Hypersensitivity

ESP: Excreted Secreted Proteins

IFA: indirect fluorescent antibody test

IgG: Immunoglobulin G

LIP: Leishmania infantum promastigotes

IFN-y: Interferon gamma

IL: Interleukin

LLT: Lymphoblastic Transformation test

NNN medium: Novy – Nicolle – Mac Neal medium

Ph. Eur: European Pharmacopeia

PSA: Promastigote Surface Antigens

SC: Subcutaneous

Sd: Standard deviation (validation of methods)

SLA: Soluble leishmania antigens

SPC: Summary of Product Characteristics

Thl: Type 1 T helper cell (lymphocyte)

TSE: Transmissible spongiform encephalopathy

CaniLeish: Quality assessment

Qualitative and quantitative particulars of the constituents

Each dose of 1 ml of vaccine contains the following:

Freeze-dried fraction:

Substances Quantity per dose
Active ingredient Excreted-Secreted proteins (ESP) Not less than 100 µq
Adjuvant Quillaja saponaria purified extract
Excipients mannitol
sucrose
Trometamol

Liquid fraction: for 1 ml of solvent

Substances Quantity per dose
Excipients Sodium chloride Water for injection 9 mg Qs 1 ml

The active substance Excreted-Secreted Proteins are constituted of parasitic proteins that are characterised by a defined protein pattern. The quantitative formulation of the vaccine relies on a quantification of the total protein content by a non-specific test. Among these proteins, some antigens have a major role for induction of immunity.

In addition to the quantitative test, other tests (based on proteomic analyses) were developed to appreciate the quality of the parasitic proteins. These tests confirmed the representativeness of the protein patterns obtained at the end of the production process.

Containers

Freeze-dried fraction: A 3 ml insulin type vial made of neutral borosilicate type I glass is used (Ph. Eur. 3.2.1.) and sealed with a buthyl elastomer rubber lyophilisation stopper and an aluminium cap.

Liquid fraction (solvent): A 3 ml insulin type vial made of neutral borosilicate type I glass is used (Ph. Eur 3.2.1.) and sealed with a buthyl elastomer rubber stopper and an aluminium cap.

Treatment:

Vials: dry heat sterilization for sterilization and depyrogenation is implemented (according to Ph. Eur. 5.1.1)

Stoppers: autoclaving takes place.

Filling and stopping are conducted under a class A environment.

The certificates of controls conducted were provided and were acceptable.

Development Pharmaceutics

Canine leishmaniosis is a widespread infectious disease in endemic areas of the Mediterranean basin, Asia and America and is a zoonosis considered as a serious veterinary problem with an increasing impact on public health. The disease is due to a protozoan parasite – Leishmania infantum ( = Leishmania chagasi in South America). The infected dogs constitute the main domestic reservoir and play a central role in the transmission of parasites to humans. The parasite is transmitted from an infected dog to a non-infected dog by the bites of sandflies of the genus Phlebotomus.

In the sandfly (vector), the parasites exist as multiplicative procyclic promastigotes and infective metacyclic promastigotes (after differentiation in the digestive tract). After transmission to the mammalian host, through the bite of infected sandflies, the parasites enter into macrophages. They persist as intracellular amastigotes living predominantly in the phagolysosome of macrophages. After initial infection, amastigotes may replicate some time before triggering an inflammatory and adaptative immune response.

Method of manufacture

Flow charts of the production processes and steps were provided.

Lyophilisate

In the first phase the excreted secreted proteins active substance is produced after culture of the Leishmania infantum. In the second phase the final product is formulated / manufactured. The formulation is based on fixed antigen content per dose and a fixed amount of adjuvant. Constituents of the excipients and adjuvant are weighed, dissolved in water and sterilised. The L. infantum ESP active substance is added under stirring and sterile conditions. The pH of the excipient and adjuvant fraction is adjusted if necessary. After formulation, the product is filled, freeze-dried and packaged. The sealed vials are stored at 5+/-3 °C in a cold room until controls and release.

Liquid fraction (solvent)

This phase starts with the preparation of the vials and stoppers for liquid preparation, the production of the diluent, then sodium chloride powder is weighed, dissolved in water for injection, and sterilised. Then diluents bottles are filled, stopped and sealed and the sealed vials are autoclaved.

Control of starting materials

Starting materials listed in a pharmacopoeia

Dimethyl sulfoxide, hydrochloric acid concentrated mannitol, sodium chloride, sodium hydrogen carbonate, sodium hydroxide, sucrose, trometamol, highly purified water and water for injection. For all the above materials certificate of analyses were provided and found acceptable.

Starting materials not listed in a pharmacopoeia

Starting materials of biological origin

Description of starting materials of biological origin

Active substance: Leishmania infantum – origin and history

Origin: isolated from a man in Morocco in 1967.

History: the strain was adapted to aseric medium and parasites were selected and cloned using defined media. The resulting parasite strain thus originates from the Leishmania infantum reference strain and was used for the construction of the seed lot system.

Master seed

Three amplifications were performed on defined and aseric medium. A cryopreservant was added on the last harvest before storage in liquid nitrogen.

Working seed

The working seed comprises the master seed undergone a few passages. The amplifications were performed on defined and aseric medium. A cryopreservant was added on the last harvest before storage in liquid nitrogen.

Controls

The following controls are preformed on the master and working seed: identity, purity, stability after passages and research for extraneous agents.

The absence of extraneous viruses was investigated in the seeds (Master seeds and working seeds) based on the Ph. Eur. monograph 062. All tests produced satisfactory results.

Hemin chloride

Use: growth factor in the culture media

Source/origin: porcine origin – animals from the Netherlands subject to ante and post-mortem examination.

Controls were considered adequate taking into account the suppliers documentation on origin/source, the gamma irradiation certificate, the tests of sterility, growing capacity, physical and chemical characteristics, assay. In order to further guarantee the absence of risk of transmission of extraneous agents through the use of porcin hemin on the vaccine production process, the applicant:

• implemented a systematic control of extraneous viruses in this raw material before irradiation treatment

• provided a validation of the irradiation method to inactivate viruses

• provided a validation of the viral clearance efficacy of the dissolution of hemin chloride in sodium hydroxide 1M for storage before its use in the vaccine production.

Based on the above data, the applicant conducted a risk assessment, which was acceptable and justified that the risk of transmission of extraneous agents through the use of hemin is close to nil.

Purified extract of Quillaja saponaria

Use: adjuvant

Source/origin: vegetal origin

Controls were considered adequate taking into account the supplier’s documentation and identification by liquid chromatography. Amongst the tests performed on adjuvant by the supplier, there is testing of the haemolytic activity and HPLC profile.

Viral risk assessment

A detailed risk assessment was presented in compliance with Ph. Eur. 5.2.5. and Ph. Eur. 5.1.7 requirements.

Considering:

• the extraneous agent testing performed on the seed lot, manufacturing process including dilutions in aseric and defined culture media,

• the use of only one starting material of biological origin (hemin chloride from porcine origin) which is carefully sourced and undergoes drastic production process as well as irradiation

• absence of use of cells or substrates that could propagate hypothetical viral infectivity,

It can be concluded that the risk of transmitting extraneous agents through the use of this vaccine is close to nil.

Starting materials of non biological origin

Starting material purchased from defined suppliers

These are powder media used as components of the Leishmania infantum culture medium. Detailed composition was provided. These media are composed of aminoacids, vitamins and other components (salts, sugars, nucleotides) all from vegetable, mineral, yeast or chemical origin.

In-house media

Leishmania infantum parasites (LIP) culture medium

• Freeze-drying excipient: Composition: sucrose , mannitol, trometamol, water for injection

Specific measures concerning the prevention of the transmission of animal spongiform encephalopathy

A detailed risk assessment was presented in accordance with Ph. Eur. monograph 1483 and existing guidance documents.

Considering:

• that seed materials are prepared in aseric and axenic media and knowing that TSE infectivity is recognised to be established and maintained in vitro with high difficulty and only with cells of neural origin,

• the absence of use of serum and starting material of TSE susceptible species for the manufacture of the vaccine,

• the indication of the vaccine for dogs, which are not susceptible to TSE by subcutaneous route It can be concluded that the risk of transmitting TSE agents through the use of this vaccine is nil.

On the basis of the above the CVMP concluded that the starting materials of animal origin used in the production of the final product comply with the current regulatory texts related to the TSE Note for Guidance (EMEA/410/01-Rev.2) and Commission Directive 1999/104/EEC.

Overall conclusion on quality

The quality part was adequately documented. The production process is relatively simple and relies on the culture of Leishmania infantum in aseric and defined media which allows the removing of Leishmania through adequate processing steps and the recovering of Excreted Secreted Proteins that constitute the active substance of the vaccine.

An overview of the production process and the controls performed during the production of the freeze-drying fraction containing the active substance and of the liquid fraction was presented. The nature of the raw materials, manufacturing process, controls and treatments applied enable to ensure sterility of the vaccine and absence of introduction of any extraneous agent, and to ensure consistency and homogeneity of the production. This is ensured by the controls performed on raw materials and vaccine products as well as process parameters investigated and recorded during the manufacture.

Many tests have been developed by the applicant which enable to:

• Specifically identify the active substance and thus specific recognition of a major protein by specific antibodies after its migration by electrophoresis is achieved allowing confirmation of the presence of this major antigen and its integrity.

• Quantify the active substance: ESP are the only proteins present in the vaccine. A non-specific protein assay allows quantification of the total amount of proteins. This quantification is used to formulate the vaccine on a fixed target. As no protein is added in the finished product, this amount can be controlled by a newly developed test performed on the final vaccine.

• Validate the purity of the active substance: An electrophoresis in defined conditions ensures the conformity of the protein pattern with the expected profile. Validation demonstrated that this kind of test allows detection of the presence of an extra-protein or the over-expression on one particular protein.

On the final product, in addition a potency test is performed which allows to test the activity of the vaccine and the ability to induce an immune response.

These tests provide clear specifications for the active substance and ensure the consistency and homogeneity of the vaccine production and hence the safety and the efficacy of the released batches.

CaniLeish: Safety assessment

CaniLeish is a freeze-dried vaccine containing Excreted Secreted Proteins of the Leishmania infantum parasite in the promastigote form, adjuvanted with a purified extract of Quillaja saponaria.

One vaccine dose is formulated with a fixed target of protein – 110 µg of ESP – adjuvanted with 60 µg of purified extract of Quillaja saponaria and reconstituted with one dose of diluent before use. The vaccine is intended for the immunisation of healthy dogs against Leishmania infantum infection. The regimen of vaccination recommends three subcutaneous injections of one dose of vaccine at 3 weeks intervals in dogs from 6 months of age onwards (primary vaccination). An annual booster immunisation with one dose of vaccine is recommended (re-vaccination scheme).

The adjuvant of the vaccine (purified extract of Quillaja saponaria) belongs to saponins and derivatives which are known to have haemolytic activity. This lytic action on erythrocytes membrane depends on the structure of the saponin itself and on the physicochemical properties of the cells. For this reason, the applicant tested the effect of CaniLeish on dog erythrocytes and haemolytical analysis including red blood cell counts were performed during safety studies.

Overall conclusion on safety assessment

The safety of the vaccination with CaniLeish was investigated primarily in Leishmania free Beagle dogs receiving 3 standard doses (as described in the SPC) or repeated administrations or an overdose (2 doses) of a vaccine formulated with an overage of antigen. Studies demonstrated that mild local reactions such as swellings associated or not with redness, pain or scabs and a weak hyperthermia may be observed after vaccination that will resolve spontaneously within few days. These reactions have been described in the SPC and are regarded as acceptable post-vaccination reactions for a canine vaccine.

The tolerance of the vaccine was good in the dogs that had been in contact with the parasite before the first injection in one of the conducted field studies and therefore considered a statement in section “Special precautions for use” was included:

“Injection of the vaccine to dogs already infected by Leishmania infantum did not show any specific adverse reactions other than those described in section 4.6”.

For the user there is a risk of self injection, which is however very low. In addition, appropriate warnings and advice on the SPC have been included. For the environment there is negligible risk that the vaccine components may cause unexpected effects to the environment. As the target species is dogs there was no requirement for residue studies.

CaniLeish: Efficacy assessment

The following information on the epidemiology, cycle of transmission, disease and immunity related to Leishmania infantum (dossier + bibliography) are considered important for better understanding the rationale followed in the laboratory and field trials presented. Therefore some important information on the disease is presented below.

Overall conclusions on efficacy

The vaccine is intended to be used in Leishmania free dogs from 6 months of age onwards to protect against Leishmania infantum after 3 vaccine injections as primo-vaccination and an annual single booster vaccination.

Studies presented in this dossier confirmed the difficulty to assess the efficacy of a vaccine against a parasitic disease with heterogeneous evolution and manifestation.

The demonstration of efficacy of the vaccine was based on a key field trial of 2 years duration involving vaccinated and control dogs submitted to natural exposure to infection in zones with high infection pressure. After these 2 years, the vaccine was demonstrated to reduce the number of dogs developing an active infection in the vaccinated group and for a dog to significantly reduce the probability to become infected and to develop a clinical disease. The benefit of the vaccination was therefore estimated in zones with high infection pressure where it may decrease the risk to develop an active infection and a symptomatic disease after contact with the parasite for vaccinated animals. In conditions with weak prevalence of the disease, no clear benefit of the vaccination could be established. This may be linked to the high number of animals needed to demonstrate the benefit in lower prevalence zone.

Laboratory studies provide limited information despite many biological investigations including humoral (IgGland IgG2, against ESP and PSA, total IgG) and cellular (lymphoblastic transformation test, IFNy ELISPOT assay, canine macrophage leishmanicidal activity) immunity evaluation. No biomarker or immunological profile correlated with protection or infection could be defined. Nevertheless data on experimental challenges showed that infection can be detected from 4 to 9 months after the experimental infection and allowed a constant and homogenous response to vaccination. However such responses could not be clearly linked to protection and future response of the dogs to infection.

Considering the diversity of evolution of the infection and the variable incubation period that may last for months, it was difficult to define for this vaccine periods such as onset or duration of immunity and protection in a laboratory studies but a duration of immunity lasting a year after the last re-vaccination and an onset of immunity of 4 weeks were supported by the field data.

CaniLeish: Benefit risk assessment

CaniLeish is a vaccine intended to reduce the incidence of asymptomatic and symptomatic forms of Leishmania infection by induction of a specific cell-mediated immunity in vaccinated dogs. It is based on the role of the Excreted Secreted Proteins of L. infantum to induce cellular immune response. The vaccine is made of a freeze-dried pellet and a diluent. The adjuvant – purified extract of Quillaja saponaria – known to participate to the activation of the cellular immune response is included in the freeze-dried fraction.

The assessment of the application dossier took into account that this vaccine is intended for a limited market and some reductions in requirements according to the guideline on Data requirement for immunological veterinary products for minor use and minor species (EMEA/CVMP/IWP/123243/2006) were implemented.

Benefit assessment

Direct therapeutic benefits

The objective is to induce sufficient immunity to Leishmania free dogs from 6 months of age to reduce the risk to develop an active infection and clinical disease after contact with Leishmania infantum.

Field trials demonstrated that the product is capable of reducing the number of Leishmania free dogs developing an active infection and significantly reduce the probability to become infected and to develop a clinical disease after contact with Leishmania infantum. The benefit of the vaccination was estimated in zones with high infection pressure where it may decrease the risk to develop an active infection and a symptomatic disease after contact with the parasite for vaccinated animals.

Additional benefits

CaniLeish is the first vaccine to be authorised for the prophylaxis against Leishmania infantum in Europe. The duration of immunity for the vaccine has been shown to be 1 year after the last re-vaccination and the onset of immunity 4 weeks.

Vaccination has been shown to be safe for Leishmania infected animals. Risk assessment Main potential risks

a) There is a risk of moderate and transient local reactions may occur such as swelling, nodule, pain on palpation or erythema. These reactions resolve spontaneously within 2 to 15 days. Other transient signs commonly seen following vaccination may be observed such as hyperthermia, apathy and digestive disorders lasting 1 to 6 days. Allergic-type reactions are uncommon and appropriate symptomatic treatment should then be administered

b) For the user there is a very low risk of self injection. Appropriate warnings and advice on the SPC will serve to minimise this risk.

c) For the environment there is negligible risk that the vaccine components may cause unexpected effects to the environment.

Specific potential risks, according to product type and application

a) Efficacy results do not show complete protection of vaccinated dogs. Despite vaccination a percentage of dogs still became infected with Leishmania infantum and from those vaccinated dogs that became infected a percentage of animals also developed clinical signs of the disease.

b) The benefit of the vaccination was established in zones with high infection pressure, whereas no clear benefit could be established in areas of low infection pressure.

c) In dogs developing Leishmaniosis (active infection and/or disease) despite vaccination, proceeding with the vaccine injections showed no benefit.

Risk management or mitigation measures

a) Appropriate warnings have been placed in the SPC to warn of the potential risks to the target animal, end user and environment.

b) Appropriate warnings have been placed in the SPC to clarify the limitations of the indication, the limitations of benefit in low infection areas and the lack of benefit in continuing the vaccination in vaccinated dogs that have developed the disease.

Evaluation of the benefit risk balance

Leishmaniosis is an important disease in dogs that is endemic in the Mediterranean countries of Europe, the Middle East and many subtropical areas of the world. In the past decade, an increased incidence of canine leishmaniosis in endemic zones as well as spread of the infection to non-endemic areas of Europe has been observed. Canines are the main reservoir for the parasites and play a relevant role in transmission to humans. The aetiological agent – Leishmania infantum – is transmitted by sandflies of the genus Phlebotomus.

In endemic areas dogs become exposed immediately. Evolution of the infection in dogs is then complex and unpredictable. Some will develop protective immunity, some remain asymptomatic after infection and may relapse later and others develop a clinical disease. It is considered that establishment of infection and development of the disease both depend on the host’s immunological response and that once the parasite escapes immunity and is able to multiply, no clearance is possible anymore. Infection may evolve over a period of a few weeks to several months toward disease patterns that can be extremely variable and polymorphic, which makes it difficult to classify dogs within specific categories.

Along with typical clinical signs and history of exposure, the diagnosis is based on microscopic identification of the parasite or PCR testing on bone marrow samples. Serological techniques may reveal active infection.

The management of dogs infected with Leishmania is currently based on sanitary and/or medical prophylaxis but up to now, both showed limited capacity to fulfil eradication, or even control of canine leishmaniosis.

Sanitary measures are based on preventing physical contact of dogs with vector, reducing the microhabitats to sandflies, and employing insecticide (environmental or topical). Despite implementation of all these measures, canine Leishmaniosis could not be reduced efficiently. Moreover culling of seropositive dogs has not proved to be efficient; although this solution was adopted in Brazil it currently has failed to prevent the number of human cases to increase.

If applied medical treatment in diseased dogs consists of symptomatic treatments associated to leishmanicidal molecules (meglumine antimoniate, aminosidine, miltefosine) which reduce or eliminate clinical symptoms but do not achieve parasitological cure. The epidemiological risk persists and dogs that respond to chemotherapy can nevertheless experience clinical relapse after the cessation of treatment or during it. Besides, these medicines have shown to have a number of disadvantages such as price, repeated injections, hepato- and nephrotoxicity, which can make compliance to treatment quite difficult to achieve.

On the basis of the above and although efficacy results have not shown complete protection of vaccinated dogs, it can be concluded that vaccination against Leishmaniosis can become a valuable and/or complementary alternative to the existing tools, despite the limits of the vaccine. Despite the fact that complete protection against Leishmaniosis or eradication of the disease cannot be achieved, this vaccine is able to reduce the risk for developing active infection and disease at the individual scale and to participate to reduction of incidence of the disease at the level of a dog population. Additionally and although the epidemiological impact of the vaccination cannot be estimated from the provided data of this application, it is nevertheless expected that improvement of the situation in dogs with regard to Leishmaniosis will also have a positive impact on human health. Finally, no risk has been linked to the use of this vaccine in dogs (included infected ones with Leishmaniosis).

Hence, the benefit-risk assessment of this vaccine appears favourable for this vaccine, within the limits highlighted in the SPC.

Conclusion on benefit risk balance

The information provided in the dossier and in response to points raised is sufficient to confirm an overall positive benefit risk balance.

Conclusion

Based on the original and complementary data presented the Committee for Medicinal Products for Veterinary Use (CVMP) concluded that the overall benefit-risk balance was considered favourable for authorisation.

 

Categories
Diseases

What Is The Role Of Inflammation In Heart Failure?

Cytokines are highly potent, endogenous peptides with autocrine and paracrine actions; they are produced by a variety of cell types. Unlike hormones, cytokines are not stored but are secreted in response to specific stimuli. TNF-alpha, lntcrleukin-1 -alpha (IL-1α), interleukin-1-beta (IL-1β), and interleukin-6 (IL-6) are classified as proinflammatory cytokines. These cytokines initiate both primary host responses and tissue repair, lnterleukin-2 (IL-2) is a potent immunostimulatory polypeptide that amplifies the immune response to antigens. Evidence suggests that proinflammatory cytokines are capable of modulating cardiovascular function through a variety of mechanisms, such as promotion of left ventricular remodeling, induction of contractile dysfunction, and uncoupling of myocardial beta-adrenergic receptors (Table Effects of Chronic Proinflammatory Cytokine Activation in Heart Failure). Several studies have shown that congestive heart failure is associated with increased circulating levels of proinflammatory cytokines. Short-term expression of cytokines in the heart may be an adaptive response to different forms of stress, whereas long-term expression may be maladaptive by producing cardiac decompensation. The cytokine hypothesis for heart failure does not imply that cytokines cause heart failure per se. However, they are potentially involved in the genesis of this pathology, and overexpression of cytokines contributes to the progression of heart failure once ventricular dysfunction ensues. Chronic sympathetic activation and increases in angiotensin H and aldosterone play a role in the overexpression of cytokines during congestive heart failure. Sustained hemodynamic overloading provokes a transient increase in proinflammatory cytokine and cytokine-receptor gene expression.

Effects of Chronic Proinflammatory Cytokine Activation in Heart Failure

Effect Mechanism Clinical Correlate
Heart
Myocyte hypertrophy Generation of reactive oxygen intermediates in cardiac myocytes; activation of fetal gene programs Cardiac hypertrophy
Left ventricular remodeling Stimulation of production of extracellular matrix proteins and increased turnover of matrix Cardiomyopathy of overload
Cardiomyocyte loss Necrosis, apoptosis Progression of heart failure
Depression of myocardial function Nitric oxide dependent; sphingomyelinase pathway; uncoupling of beta adrenoreceptors; abnormal mitochondria energetics Decreased contractility
Exacerbated inflammatory response Cytokine cascade Myocarditis
Skeletal Muscle
Myopathy Free radical and nitric oxide overproduction; endothelial dysfunction Reduced blood flow in muscles, exercise intolerance
Decreased skeletal mass Apoptosis Cardiac cachexia
Other Effects
Anorexia Cardiac cachexia
Pulmonary edema Dyspnea

 

The main stimulus for cytokine activation in congestive heart failure is not known. The heart is primarily involved and could be the main source of proinflammatory cytokines, because the failing myocardium is capable of producing TNF-alpha. It has also been demonstrated that pressure overload stimulates the synthesis of TNF-alpha messenger ribonucleic acid (mRNA). Myocardial stretch induces mRNA production by myocytes. Another potential stimulus for an increase in the production of TNF-alpha by the failing heart is extramyocardial cytokine release caused by tissue hypoxia. Tissue hypoxia and the production of free radicals are potent stimuli for the generation of cytokine release via nuclear factor-kappa-B (NF-kappa-B)-dependent pathways. Cytokines are expressed in the myocardium in end-stage heart failure to a much greater degree than in patients with recent onset of symptoms. Plasma levels of TNF-alpha correlate with mRNA expression in the myocardium and thus may serve as an appropriate marker of myocardial cytokine activation. Whether the production of cytokines in the failing human heart precedes the elevation of cytokines in the plasma remains undefined.

The bowel could also be a source of proinflammatory cytokines during congestive heart failure. The intestinal wall edema and ischemia that occur during congestive heart failure favor bacterial translocation and may cause the release of endotoxins, with subsequent immune activation. It has been shown that during acute, edematous exacerbation of CHF, endotoxin and cytokine concentrations increase but can be normalized by diuretic therapy.

Tumor Necrosis Factor Alpha

TNF-alpha is a proinflammatory cytokine that exerts negative inotropic effects in vivo and in vitro. Acute negative inotrope results from disruption of calcium transients, whereas chronic effects are associated with induction of inducible nitric oxide synthase (iNOS) and are due to NO-induced myofilament desensitization to calcium. TNF-alpha also can produce left ventricular remodeling, hypertrophy and apoptosis, pulmonary edema, and cardiomyopathy. It stimulates production of other endogenous pyrogens, such as IL-ip. The main known stimuli that prompt adult mammalian myocardial cells to produce tumor necrosis factor are endotoxins, hypoxia, and increased mechanical stress. NF-kappa-B can also participate in the production of TNF-alpha. Oxidative stress activates NF-kappa-B, which binds to a tumor necrosis factor promoter, increasing TNF-alpha transcription. Mild acute increases in TNF-alpha are an adaptive response to stress; they protect the heart during ischemia and favor remodeling during infarcts and adaptive growth during hemodynamic overload. Severe acute increases lead to myocarditis as a result of an exacerbated inflammatory response, and chronic increases are maladaptive, favoring cardiac decompensation and apoptosis.

Cats with naturally occurring congestive heart failure have increased concentrations of TNF-alpha. Increases in the TNF-alpha concentration have been independently associated with a poorer prognosis for congestive heart failure. TNF-alpha is produced in the heart by cardiac myocytes and resident macrophages under conditions of cardiac stress. Normal hearts do not produce TNF-alpha, but failing human hearts make abundant quantities. The source of cardiac TNF-alpha appears to be at least partly attributable to production by the cardiac myocyte. TNF-alpha plays an important role in the development of heart failure. Administration of TNF-alpha to experimental animals and transgenic overexpression of TNF-alpha lead to congestive heart failure. Mice that overexpress TNF-alpha recapitulate heart failure and a dilated cardiomyopathy state in other species shows (1) four-chamber dilatation, (2) myocyte hypertrophy, (3) interstitial infiltrates, (4) extracellular matrix remodeling with fibrosis, (5) diminished beta-adrenergic responsiveness, and (6) premature death. Attenuation of the biologic activity of TNF-alpha abrogates the development of congestive heart failure in experimental model systems. Unfortunately, anti-TNF strategies to date have not demonstrated salutary benefits in large, multicenter, randomized and placebo-controlled clinical trials in patients with symptomatic heart failure.

Interleukins

Interleukin-1 (IL-1) mediates immune response and the production of inflammatory responses through an increase in prostaglandins, and it may be a basal part of the overactivated cytokine cascade during congestive heart failure. IL-1 appears capable of modulating myocardial function. It exerts a potent antiprolifera-tive effect on cardiac fibroblasts but induces cardiac myocyte hypertrophy. IL-lβ is increased during CHF; it decreases myocardial contractility by stimulating iNOS, and it may uncouple beta adrenoreceptors from adenylatecyclase, one of the mechanisms of heart failure progression. The negative inotropic effect of IL-1 appears to be mediated, at least partly, by production of nitric oxide or by the activation and release of interleukin-18, a member of the IL-1 family. IL-1 induces synthesis by T lymphocytes of interleukin-2 (IL-2), an endogenous T-cell mitogen that enhances T-cell proliferation. IL-2 thus amplifies the immune response and stimulates the production of interferon-gamma and the release of other inflammatory factors (e.g., TNF-alpha). IL-2 levels are increased in human patients with dilated cardiomyopathy and in their relatives, with left ventricular enlargement usually being higher in patients with congestive heart failure. Interleukin-6 (IL-6) is a multifunctional cytokine that mediates both immune and inflammatory responses. It is also a promoter of cardiomyocyte hypertrophy and a negative inotrope that is elevated in patients with heart failure, especially those with cardiac cachexia or severe congestive heart failure. In human patients with CHF, IL-6 is a predictor of mortality independent of etiology, the sodium concentration, the severity of heart failure, and the ejection fraction.

Nuclear Factor— Kappa-B

During CHF, oxidative stress, increased expression of TNF-alpha, and an increase in the angiotensin II concentration serve to activate NF-kappa-B. NF-kappa-B is a redox-sensitive transcription factor that is critical to initiation of the co-ordinated expression of classic components of the myocardial inflammatory response, including increased expression of proinflammatory cytokines (e.g., TNF-alpha, IL-6), NO, chemokines, and adhesion molecules. NF-kappa-B is an important player in inflammation during heart failure. Activation of NF-kappa-B initiates gene transcription of several substances that can lead to cardiovascular injury. NF-kappa-B signaling also plays an important role in myocardial growth, and its inhibition attenuates cardiomyocyte hypertrophy. Myocardial cells from patients with heart failure exhibit activation of NF-kappa-B and increased expression of genes it regulates (e.g., TNF-alpha, iNOS). Elevation of NF-kappa-B seems to occur independent of the etiology of heart failure but appears to be related to the severity of congestive heart failure. NF-kappa-B can activate cell death pathways, and TNF-alpha-induced apoptosis is associated with an increase in NF-kappa-B. However, blocking of NF-kappa-B in this setting paradoxically exacerbates cell death. It is not known if NF-kappa-B activates antiapoptotic factors. The paradoxical effect of activating detrimental molecules while protecting cells may be related to the inflammatory program mediated by NF-kappa-B; it generates toxic molecules that can kill invading micro-organisms without damaging host cells.

Reactive Oxygen Species

Increases in angiotensin II induce production of reactive oxygen species. An important effect of angiotensin II is activation of the NAD(P)H oxidase, a major source of reactive oxygen species (ROS) production by vascular cells. Reactive oxygen species are the end result of univalent reductions in oxygen that produce superoxide anion, hydrogen peroxide, and water. ROS influence both normal and abnormal cellular processes, including cellular growth, hypertrophy, remodeling, lipid oxidation, modulation of vascular tone, and inflammation. The increase in cellular ROS contributes to the pathogenesis of vascular disease by altering endothelial cell function; enhancing smooth muscle cell growth and proliferation; stimulating inflammatory proteins, including macrophage chemoattractant agents, growth factors and cytokines; and modulating matrix remodelling. These ROS can be released from the cardiac myocyte mitochondria, and chronic release of ROS recendy was linked to the development of left ventricular hypertrophy and progression of heart failure. The release of ROS is required for the normal physiologic activity of cardiac cells, but abnormal activation of nonphagocytic NAD(P)H oxidase in response to neurohormones and cytokines (angiotensin II, norepinephrine, TNF-alpha) has been shown to contribute to cardiac myocyte hypertrophy. The fibrosis, collagen deposition, and metalloproteinase activation involved in the remodeling of a failing myocardium depend on ROS released during the phenotypic transformation of fibroblasts to myofibroblasts that is associated with progression of end-stage heart failure. Studies of genetically altered mice have shown that activation of the NAD(P)H oxidase by angiotensin II contributes to hypertension and left ventricular hypertrophy.

The cytokine hypothesis for heart failure suggests that heart failure progresses because cytokine cascades that are activated after myocardial injury exert deleterious effects on the heart and circulation. This hypothesis does not imply that cytokines cause CHF, but rather that overexpression of cytokines contributes to the progression of heart failure once left ventricular dysfunction ensues. TNF-alpha and IL-6 become activated after left ventricular injury or myocardial stretch. These stress-activated cytokines can exert autocrine and paracrine effects in the myocardium by binding to specific cytokine receptors. If cytokine expression is excessive, these molecules may produce left ventricular dysfunction and left ventricular dilatation. It is further postulated that cytokines, when overproduced, may spill over into the circulation, leading to secondary activation of the immune system, which is then capable of amplifying the cytokine signal in the periphery. There is an easily recognizable overlap between the neurohormonal and cytokine hypothesis. However, there are likely to be important differences in the mechanisms that initiate overexpression of these molecules, as well as differences in the biologic effects that these molecules exert.

Categories
Veterinary Medicine

Canine Parvovirus

1. What are the common clinical signs in dogs with canine parvovirus (CPV)?

• Lethargy

• Vomiting

• Inappetence

• Fever

• Acute-onset diarrhea

• Profound neutropenia (white blood cells < 1000/mm3)

Puppies between the ages of 6 weeks to 6 months are most commonly affected. In a Canadian study, sexually intact dogs had a 4-fold greater risk than spayed or neutered dogs, and the months of July, August, and September had a 3-fold increase in cases of canine parvovirus.

2. What systems other than the GI tract are involved with canine parvovirus?

In a study of dogs with the GI form of canine parvovirus, arrhythmia was diagnosed in 21 of 148 cases, including supraventricular arrhythmias and conduction disturbances. Some dogs developed significant enlargement of the cardiac silhouette and other radiographic cardiac abnormalities. CPV can replicate in bone marrow, heart, and endothelial cells; replication in endothelial cells of the brain produces neurologic disease.

3. What other infectious diseases may be mistaken for canine parvovirus infection?

Infection with Salmonella sp., Campylobacter sp., or Escherichia coli may mimic canine parvovirus symptoms and also cause the shift in white blood cells. CPV infection also may be confused with hemorrhagic gastroenteritis (HGE), although HGE is seen most commonly in smaller breeds and usually resolves in 24 hours. Coronavirus often presents with GI signs, but neutropenia tends to resolve more rapidly than with canine parvovirus infection. Clinical signs of infection with coronavirus are usually seen only in dogs also infected with parvovirus.

4. What is the primary mode of transmission of canine parvovirus?

The number of viral particles in the feces is quite high; the fecal-oral route is the most likely means of transmission. No studies of vomitus have been done, but it probably contains viral particles.

5. How does canine parvovirus infect the intestines?

Viral replication occurs in the oropharynx during the first 2 days of infection, spreading to other organ systems via the blood. By the third to fifth day a marked viremia develops. The virus reaches the intestinal mucosa from the blood rather than from the intestinal lumen. Clinical signs are seen 4-5 days after exposure, and the incubation period ranges from 3-8 days, with shedding of the virus on day 3.

6. Where does canine parvovirus replicate in the body?

The virus replicates in rapidly dividing cells, which include lymph nodes, spleen, bone marrow, and intestines. In the intestines, viral replication kills the germinal epithelium of the intestinal crypts, leading to epithelial loss, shortening of the intestinal villi, vomiting, and diarrhea. Lymphoid necrosis and destruction of myeloproliferative cells result in lymphopenia and, in severe cases, panleukopenia. Only about one-third of canine parvovirus cases have defined neutropenia or lymphopenia.

7. How has the clinical presentation of CPV infection changed since the 1970s?

There are several strains of canine parvovirus, including the original strain, CPV-1; the minute virus; and the most severe strain, CPV-2 (with subtypes 2a and 2b). CPV-2b is now the most common strain in the United States. CPV-1, which dominated in the 1970s, caused a milder disease associated with fever and a larger window for treatment. CPV-2b causes a more explosive acute syndrome that affects young dogs 6-12 weeks of age, making the window between the first signs of GI upset and treatment much narrower and more critical. There have been no major changes in presentation in the past 6 years; lethargy, listlessness, and bloody diarrhea are the most common presenting signs. Other diseases associated with or mistaken for canine parvovirus are canine distemper virus, coccidial or giardial infection, hookworms, roundworms, or a combination of these.

8. When and how does one diagnose canine parvovirus?

CPV is most easily diagnosed with a fecal enzyme-linked immunosorbent assay (ELIS A). If the test is negative but canine parvovirus is still suspected, isolate the animal and run the test again in 48 hours. The virus is not usually shed until day 3, and conscientious clients may bring the animal to the hospital at the first sign of illness. The period during which canine parvovirus is shed in the feces is brief, and the virus is not usually detectable until day 10-12 after infection. Usually the acute phase of illness has passed by this time. Modified live canine parvovirus vaccines shed in the feces may give a false-positive ELISA result 4-10 days after vaccination.

One also may use a combination of ELISA, complete blood count, and radiographs to diagnose canine parvovirus. Radiographs may help to rule out the possibility of an intestinal foreign body, and detection of generalized ileus with fluid-filled loops of intestines supports the diagnosis of canine parvovirus. Be sure to have enough antigen in the fecal sample when running the ELISA; watery stools may dilute the antigen and give a false-negative result.

Conclusive proof of canine parvovirus infection is made with electron microscope identification of the virus.

9. What are the recommendations for inpatient care of dogs with CPV?

1. Aggressive fluid therapy. Correct dehydration and provide intravenous maintenance fluid volumes of a balanced crystalloid solution. Make every attempt to replace continuing losses (vomitus and diarrhea) with equal volumes of crystalloid fluids. The easiest method is simply to estimate the volume lost and double your estimate. Continuing losses need to be replaced at the time that they occur. Use Normosol with at least 20 mEq/L of potassium chloride supplementation. Monitor glucose level. If necessary, add 2.5-5% dextrose to intravenous fluids. A 5% dextrose solution creates an osmotic diuresis, but it also allows assessment of progress in dealing with a septic case (glucose increases when the animal receives 5% dextrose if the sepsis is resolving). Low levels of magnesium chloride may be added to fluids to help correct unresponsive hypokalemia.

2. Antibiotic therapy. Broad-spectrum parenteral antibiotics are recommended because of disruption of the mucosal barrier and potential sepsis. Bacteremia is identified in 25% of dogs infected with parvovirus. A combination of ampicillin and gentamicin is recommended. Most veterinarians use only a first-generation cephalosporin in dogs without neutropenia or fever and reserve ampicillin and gentamicin or amikacin for dogs with signs of sepsis. One should be cautious about using an aminoglycoside because of renal toxicity.

3. Endotoxin-neutralizing products. Endotoxin-neutralizing products may be administered along with antibiotic therapy. The rationale for their use is based on the large population of gram-negative bacteria; by killing the bacteria, antibiotic therapy may shower the body with en-dotoxin, thus exacerbating the canine parvovirus condition. Studies have shown that endotoxin-neutralizing products decrease the incidence of septic shock. They may be diluted (4 ml/kg) with an equal volume of saline and administered intravenously over 30-60 minutes. Dogs who have recovered from parvovirus infections can be a good source for serum. Serum should be collected within 4 months of infection.

4. Antiemetics. Metoclopramide is the drug of choice. Phenothiazine derivatives should be used with caution and only after adequate volume replacement is initiated to avoid severe hypotension. Antiemetics are especially useful when continued vomiting makes it difficult to maintain hydration or electrolyte balance.

5. Motility modifiers. The use of motility modifiers is controversial. Anticholinergic anti-diarrheal medications may suppress segmental contractions and actually hasten transit time. Narcotic analgesics and synthetic opiates are better choices but should be reserved for severe or prolonged cases because slowing the flow through the intestine may increase toxin absorption.

6. Nothing per os (NPO). Begin a slow return to water 24 hours after the animal stops vomiting, and slowly progress to gruel made from a bland diet.

10. What is granulocyte colony-stimulating factor (GCSF)? What role does it have in treating dogs with CPV?

Granulocyte colony-stimulating factor selectively stimulates release of granulocytes form the bone marrow. Preliminary studies have shown that it reduces morbidity and mortality due to canine parvovirus. Unfortunately, it is available only as a human drug and is expensive, but when the positive benefits are considered, its use may be justified.

11. Does interferon benefit a dog with parvovirus infection?

Interferon given parenterally has been shown to be beneficial. The suggested dosage of human recombinant interferon is 1.3 million units/m2 subcutaneously 3 times/week.

12. How is a dog with canine parvovirus monitored?

Monitor respiration and central venous pressure (CVP) to prevent overhydration. With osmotic diarrhea the animal loses protein. If abdominal or extremity swelling is observed or if the total solids drop by 50% from admission values or go below 2.0 gm/dl, the animal should be supplemented with either 6% hetastarch or plasma to maintain colloid oncotic pressures. Blood glucose should be monitored at least 4 times/day on the first two days. Glucose level may drop precipitously and suddenly. Most importantly, weigh the dog at least twice each day. If adequate crystalloid replacement is provided, body weight does not decrease from initial values. Ideally body weight should increase at a rate comparable to the degree of dehydration originally assessed. Dogs that can hold down water for 12 hours may be offered a gruel made from bland foods. Most dogs force-fed by hand will vomit. This response may be physical or psychological (association of food with vomiting). Nasogastric tubes seem to help this problem. Metoclopramide speeds gastric emptying, acts as an antiemetic, and decreases gastric distention when added to the liquid diet. Dogs that are not vomiting should be offered food even if the diarrhea has not totally stopped. A low-fat, high-fiber diet is a good choice to stimulate intestinal motility.

13. How do you know when to send a dog home?

The dog should stay in the hospital for 12 hours after it has ingested solid food with no vomiting. Clients should report immediately any vomiting in the next 7 days or refusal to eat for 24 hours. A high-fiber diet is recommended for reducing diarrhea. A recheck appointment in 1 week with a stool sample helps the clinician to assess progress.

14. What recommendations do you offer to clients who have had a CPV-infected animal in their household and now want a new pet?

Prevention involves a proper vaccination regimen, limited exposure to other animals (especially in puppies less than 12 weeks of age), cleaning contaminated areas with bleach (allowing prolonged contact time), and vacuuming all surfaces with which the previous pet came into contact (rugs, carpet, walls, furniture). Newer higher-titer vaccines (some of which may be started as early as 4 weeks) are helpful. Generally, one should wait at least 1 month before bringing the new pet into the home. It is doubtful that the environment (especially outdoors) will ever be completely free of the virus. Canine parvovirus is a hardy and ubiquitous organism.

15. How long can a dog with CPV be expected to retain immunity?

A dog that has recovered from canine parvovirus can maintain life-long immunity.

16. What is the recommended vaccination schedule for dogs? Is it the same for every breed?

Some breeds are more susceptible to canine parvovirus than others. Rottweilers, American pitbull terriers, Doberman pinschers, and German shepherds are the most susceptible, whereas toy poodles and Cocker spaniels are less susceptible. The new higher-titer vaccines have a higher antigen level and a more virulent vaccine strain that can overcome maternal antibodies, unlike the older lower-titer vaccines. These vaccines narrow the window of infection, especially for susceptible breeds. The vaccination protocol for the new high-titer vaccines is 6, 9, and 12 weeks. Susceptible breeds should be vaccinated only with the high-titer canine parvovirus vaccine and then with a combination vaccine at 6-8, 12, and 16 weeks. For less susceptible breeds, the combination vaccines at 6-8, 12, and 16 weeks should be adequate. Some parvovirus vaccines are approved for use as early as 4 weeks of age.

17. How do you manage a sick puppy when the client is unwilling to pursue hospital treatment for CPV?

Canine parvovirus can be treated on an outpatient basis. A combination of dietary restriction, subcutaneous fluids, and, in some cases, GI medications may be used with a follow-up appointment in 1-3 days. Outpatient recommendations include the following:

• Small, frequent amounts of fluid

• Bland food

• Oral antibiotics

• Strong recommendation to have the pet reexamined and admitted for therapy if vomiting returns or anorexia persists

Nine of ten clients bring the dog back for inpatient care shortly after taking it home. Before treating an outpatient, remember that mildly depressed dogs may have a rectal temperature of 106° F and a blood glucose of 30 mg/dl in 12 hours or less.

18. Should a dog with suspected CPV be hospitalized and placed in isolation?

Undoubtedly hospitalization provides the best chance for survival. Isolation is more controversial. In most veterinary hospitals, isolation means that the animal is housed in a section of the hospital that is not staffed at all times. The adage “out of sight, out of mind” has led to the demise of many CPV-infected dogs. Experience with housing dogs with canine parvovirus in the critical care unit at the Veterinary Teaching Hospital of Colorado State University has shown that nosocomial infections can be avoided with a common-sense approach to patient management. The animal is placed in the least traveled area and has its own cleaning supplies; gowns and gloves are worn each time the animal is handled; and the animal’s cage is kept as clean as humanly possible. These procedures are no different from those in an isolation area. By being housed in an area where constant attention can be given, the animal receives adequate fluid replacement therapy and is monitored for changes, which occur rapidly.

19. How is nutrition provided for vomiting dogs?

Tough question! Dogs that have not eaten for 3-5 days are probably in a negative nitrogen balance, and certainly intestinal villi have undergone atrophy if not already destroyed by the canine parvovirus. The sooner patients begin receiving oral nutrition, the more rapidly they will recover. In addition, micronutrient therapy for the intestinal mucosa is required for maintenance of the mucosal barrier. Without this barrier, sepsis and bacteremia are more likely. Unfortunately, the only means to provide micronutrients is the oral route.

Glucose therapy does not provide nutritional support. It is best to think of dextrose as simply a source of water. One liter of 5% dextrose solution contains a mere 170 kcal. Increasing dextrose concentrations beyond 5% usually results in glycosuria and osmotic diuresis.

Patients that have not eaten for several days are primed for fat metabolism; thus, Intralipid (20%) may be added to fluids. It should be administered through a central IV catheter and requires strict aseptic management, which may be difficult if the patient is in an isolation area of the hospital.

For dogs that retain water without vomiting, glutamine may be added directly to the water bowl. Often placing electrolyte solutions in the water bowl is a good way to start the animal drinking. Placing dextrose in these fluids or even using commercial solutions such as Ensure-Plus in the bowl helps to provide intestinal nutrients.

20. Should parvovirus antibody levels be measured to check the immune status of the puppy?

Although antibodies to parvovirus can be measured, a negative titer does not necessarily mean that the dog is susceptible to canine parvovirus. Repeated revaccination of antibody-negative dogs usually does not result in significant titers.

Categories
Diseases

Viral Enteritides

Most viral enteritides of dogs and cats, especially the parvovirus infections, cause an acute and usually self-limiting diarrhea, although severe cases in young or immunocompromised patients may be fatal. Canine parvovirus infection is described here as the index case for viral enteritides.

Canine Parvovirus

Canine parvovirus type 2 (CPV-2) is a highly contagious cause of acute enteritis. It emerged as a pathogen in the late 1970s, perhaps from a mutation of a feline vaccine as it is related to feline panleukopenia and mink enteritis viruses. CPV-2b has emerged as the most prevalent antigenic variant. There have been reports of cats being infected with canine parvovirus type 2, but the severity of signs is much reduced.

Infected dogs shed massive quantities of virus particles in feces during the acute illness and then for about 8 to 10 days afterward. Parvovirus is extremely stable and can remain infectious in the environment for many months. Infection is acquired via the fecal-oral route and is more common in the summer months. The virus has an affinity for rapidly dividing cells and localizes to the intestine (crypt cells), bone marrow, and lymphoid tissues. It causes apoptotic cell death, leading to intestinal crypt necrosis and severe diarrhea, leukopenia, and lymphoid depletion.

Clinical Findings

Clinical signs of diarrhea typically occur 4 to 7 days after infection. Anorexia, depression, fever, vomiting, diarrhea (often profuse and hemorrhagic), and dehydration are common. Hypothermia and disseminated intravascular coagulation (DIC) are associated with terminal bacterial sepsis or endotoxemia. Dogs of any age can be affected, but the incidence of clinical disease is highest in puppies between weaning and 6 months. Puppies younger than 6 weeks usually are protected by maternal antibody. In dogs older than 6 months, males are more likely to become infected than females. Overcrowding, intestinal parasitism, concurrent infection with distemper virus, coronavirus, Giardia, Salmonella, or Campylobacter spp. can increase the severity of illness.

Puppies infected in utero or shortly after birth may develop myocarditis and either die suddenly or develop cardiomyopathy if maternal antibody is absent. This situation rarely arises nowadays because widespread vaccination and infection have left few seronegative dams. Yet death still occurs, especially in young puppies, and particularly in susceptible breeds such as rottweilers, Dobermans, English springer spaniels, and American pit bull terriers. Death is usually attributed to dehydration, electrolyte imbalances, hypercoagulability, endotoxic shock, or overwhelming bacterial sepsis related to mucosal barrier disruption and leukopenia. Infected dogs are immunosuppressed and susceptible to catheter infections. Endotoxemia, TNF activity, coliform septicemia, and proliferation of enteric C. perfringens determine morbidity and mortality.

Diagnosis

Parvovirus should be suspected in young dogs with sudden onset of vomiting and diarrhea, especially if they are also depressed, febrile, or leukopenic or if they have been in contact with infected dogs. Leukopenia (often 500 to 2000 white blood cells per microliter) may be detected in up to 85% of field cases and is very suggestive of parvovirus infection. It reflects neutropenia and lymphopenia. Neutropenia results from impaired bone marrow production with concurrent r. eutrophil loss through the damaged gastrointestinal tract, and severe neutropenia crudely correlates with a poor prognosis.

In the absence of leukopenia, clinical signs are indistinguishable from those of other bacterial or viral enteritides, gastrointestinal foreign bodies with peritonitis, or intussusception. Abdominal radiographs may reveal non-specific gas and fluid accumulation, and ileus. Biochemical abnormalities often include hypokalemia, hypoglycemia, prerenal azotemia, and increased bilirubin or liver enzymes.

Definitive diagnosis requires demonstration of canine parvovirus type 2 virus (orviral antigens) in the feces. Fecal enzyme-linked immunosorbent assay is regarded as an accurate and specific diagnostic test but is most sensitive in the first 7 to 10 days when virus excretion is greatest. Single anti-CPV antibody determination in serum (by hemagglutination inhibition) is not useful for diagnosis except in the presence of typical clinical signs in an unvaccinated animal. A rising IgG titer by paired serology provides only a retrospective diagnosis. Serum IgM analysis may provide evidence of recent infection.

Treatment

Treatment is supportive and is similar to regimens used in most animals with severe gastroenteritis. Intravenous fluid therapy usually is indicated and is continued until vomiting stops and oral intake resumes. A balanced electrolyte solution (e. g., lactated Ringer’s solution) supplemented with potassium and 2.5% glucose is often used. Plasma or whole blood infusions are given to treat severe hypoproteinemia or anemia. Antibiotics are used to control potentially fatal sepsis (see above).

Traditionally, oral intake is withheld until vomiting has stopped for at least 24 hours; this may take 3 to 5 days in severe cases. Rather than avoid the oral route completely, it may be better to trickle feed small amounts of glutamine-containing solutions to reduce bacterial translocation. Once vomiting has been controlled, small amounts of a bland diet are fed initially. Frequent or persistent vomiting can be managed with intermittent injections or constant-rate infusion of metoclopramide, once intestinal obstruction has been ruled out. Phenothiazines (e. g., chlorpromazine) can be used if metoclopramide is ineffective and the animal has been rehydrated.

Administration of corticosteroids is of unproven benefit and is probably best limited to dogs with severe endotoxic shock. Flunixin meglumine is best avoided because of its adverse effects on the gastrointestinal tract and kidneys. Antiendotoxin therapy has been useful in some patients, but the timing of antiendotoxins in relation to antibiotic therapy may be important. Because antibiotics may increase endotoxin liberation, it may be preferable to administer antiendotoxin serum before antibiotics. However, one study showed that the use of the antiendotoxin rBPI21 had no beneficial effect on survival, and in another study, use of antiendotoxin was correlated with decreased suvival. Administration of recombinant human granulocyte colony-stimulating factor (G-CSF) to neutropenic parvoviral enteritis patients may raise neutrophil counts but is of no clinical benefit, because the endogenous granulocyte colony-stimulating factor concentration is already elevated. In contrast, administration of feline interferon-omega was found to improve clinical signs and reduce mortality.

Prognosis

Severe infection and leukopenia are associated with a high mortality rate, but most dogs with parvovirus recover if dehydration and sepsis are treated appropriately. Complications include hypoglycemia, hypoproteinemia, anemia, intussusception, and secondary bacterial or viral infections.

Prevention

Prevention is achieved by limiting exposure to the virus, adequate disinfection (1:32 dilution of sodium hypochlorite bleach), and vaccination. Vaccination is an effective means of preventing and controlling canine parvovirus type 2, but maternal antibody interference is a problem. Maternally derived antibodies (MDAs) can persist for up to 18 weeks and can interfere with vaccination, although most modern vaccines can overcome maternally derived antibodies by 10 to 12 weeks of age. Modified live canine parvovirus type 2 vaccines are most commonly used; killed vaccines provide less duration of immunity but may be recommended in pregnant dogs and puppies younger than 5 weeks. Vaccines may differ in efficacy; low-passage, high-titer vaccines are considered most effective, and only one injection at or after 12 weeks may be needed. In susceptible breeds and dogs in high-risk areas, vaccination may begin at 6 to 8 weeks of age and be repeated every 3 to 4 weeks until 18 weeks of age. There is good correlation between the antibody titer and resistance to infection with canine parvovirus. Annual revaccination is currendy recommended.

Feline Parvovirus (Feline Panleukopenia)

Feline panleukopenia is a highly contagious infection of cats that causes severe acute diarrhea and death, similar to canine parvovirus. Mortality in young kittens is high (50% to 90%), therefore the prognosis is guarded until the vomiting and diarrhea stop and the leukopenia resolves.

Canine Coronavirus

Canine coronavirus (CCV) can cause diarrhea of variable severity in dogs. Transmission is by the fecal-oral route. The incubation period is 1 to 4 days, and infected dogs may shed virus intermittently for months after clinical recovery. However, the significance of coronavirus as a primary pathogen is unclear. Experimental inoculation is associated with only mild disease and canine coronavirus infection, and antibodies against canine coronavirus are present in many healthy and diarrheic dogs. Infection is very prevalent, particularly in animal shelter and laboratory dogs. Most canine coronavirus infections are probably subclinical, although severe enteritis may occur in dense populations or with concurrent infections. In such situations, vaccination may be helpful.

Feline Enteric Coronavirus

Feline enteric coronavirus (FECV) is ubiquitous in the cat population. Mild to moderately severe diarrhea, which may be associated with weight loss, is seen in kittens infected with feline enteric coronavirus. Inapparent infection is common in normal cats, many of which shed FECV in feces and are seropositive. Feline enteric coronavirus infection is important, because enteric coronaviruses may mutate to feline infectious peritonitis virus (FIPV).

Intestinal Feline Infectious Peritonitis

An unusual manifestation of feline infectious peritonitis (FIP) of isolated mural intestinal lesions has been reported. Predominant clinical signs were diarrhea and vomiting, and all cats had a palpable mass in the colon or ileocecocolic junction. Affected intestine was markedly thickened and nodular, with multifocal pyogranulomas extending through the intestinal wall.

Feline Immunodeficiency Virus

Infection with feline immunodeficiency virus (FIV) is associated with a 10% to 20% incidence of chronic enteritis. Although secondary and opportunistic infections may be responsible for signs, sometimes no other etiologic agent can be identified. Anorexia, chronic diarrhea, and emaciation are typical. Palpably thickened bowel loops reflect chronic enteritis with transmural granulomatous inflammation.

Feline Leukemia Virus

Among its many manifestations, feline leukemia virus (FeLV) infection can be associated with fatal peracute enterocolitis and lymphocytic ileitis.

Torovirus

A torovirus-like agent has been isolated from the feces of cats afflicted with a characteristic syndrome of chronic diarrhea and protruding nictitating membrane. However, a clear association with clinical signs was not demonstrated.

Categories
Diseases

Inflammatory Bowel Disease

Inflammatory bowel disease is a collective term that describes a group of disorders characterized by persistent or recurrent gastrointestinal signs and histologic evidence of intestinal inflammation on biopsy material. The disease bears little resemblance to inflammatory bowel disease (Crohn’s disease and ulcerative colitis) of humans, and indiscriminate use of the term “IBD” is no more useful than a dermatologist making a diagnosis of “chronic dermatitis. Although a number of recognized diseases are associated with chronic intestinal inflammation (Box Causes of Chronic Small Bowel Inflammation), the cause of idiopathic inflammatory bowel disease is, by definition, unknown. Variations in the histologic appearance of the inflammation suggest that idiopathic inflammatory bowel disease is not a single disease entity, and the nomenclature reflects the predominant cell type present. Lymphocytic-plasmacytic enteritis (lymphocytic-plasmacytic enteritis) is the most common form reported; eosinophilic (gastro-) enteritis (EGE) is less common; and granulomatous enteritis is rare. Neutrophilic infiltration is a feature of human inflammatory bowel disease but is infrequent in idiopathic inflammatory bowel disease of dogs and cats.

Causes of Chronic Small Bowel Inflammation

Chronic infection

  • Giardia sp.
  • Histoplasma sp.
  • Toxoplasma sp.
  • Mycobacteria sp.
  • Protothecosis
  • Pythiosis
  • Pathogenic bacteria (Campylobacter, Salmonella spp., pathogenic Escherichia coli)

Food allergy

Small bowel inflammation associated with other primary gastrointestinal diseases

  • Lymphoma
  • Lymphangiectasia

Idiopathic causes

  • Lymphocytic-plasmacytic enteritis (lymphocytic-plasmacytic enteritis)
  • Eosinophilic gastroenterocolitis (EGE)
  • Granulomatous enteritis (same as regional enteritis?)

Clinical Presentation

Idiopathic inflammatory bowel disease is a common cause of chronic vomiting and diarrhea in dogs and cats, but its true incidence is unknown. In reality it is often overdiagnosed because of difficulties in interpretation of histopathologic specimens and failure to eliminate adequately other causes of mucosal inflammation. No apparent gender predisposition occurs in dogs and cats, but in both species inflammatory bowel disease is most common in middle-aged animals. gastrointestinal signs, which may have been variably controlled by dietary manipulation, are sometimes seen from an earlier age. Although inflammatory bowel disease can potentially occur in any dog or cat breed, certain predispositions are recognized, such as lymphocytic-plasmacytic enteritis in German shepherds and Siamese cats, lymphoproliferative enteropathy in basenjis, and protein-losing enteropathy / protein-losing nephropathy (protein-losing enteropathy / PLN) in soft-coated wheaten terriers. Shar Peis often have a severe lymphocytic-plasmacytic enteritis with hypoproteinemia and extremely low serum cobalamin concentrations. In cats an association, called triaditis, has been reported for inflammatory bowel disease, lymphocytic cholangitis, and chronic pancreatitis.

Clinical Signs Associated with Inflammatory Bowel Disease

Vomiting of bile with or without hair in cats and grass in dogs

Hematemesis

Small intestinal — type diarrhea

  • Large volume
  • Watery
  • Melena

Thickened bowel loops

Large intestinal — type diarrhea

  • Hematochezia
  • Mucoid stool
  • Frequency and tenesmus

Abdominal discomfort / pain

Excessive borborygmi and flatus

Weight loss

Altered appetite

  • Polyphagia
  • Decreased appetite / anorexia
  • Eating grass

Hypoproteinemia / ascites

Vomiting and diarrhea are the most common clinical signs, but an individual case may show some or all of the signs in Box Clinical Signs Associated with Inflammatory Bowel Disease.Sometimes an obvious precipitating event (e. g., stress, dietary change) is present in the history, but clinical signs may wax and wane. The nature of signs crudely correlates with the region of the gastrointestinal tract affected: gastric signs are more common if gastric or upper small intestine inflammation is present; in cats, vomiting is often the predominant sign of small intestinal IBD; and Li-type diarrhea may be the result of colonic inflammation or may result from prolonged small intestine diarrhea. The presence of blood in the vomit or diarrhea is associated with more severe disease, especially eosinophilic inflammatory infiltrates. Severe disease is associated with weight loss and protein-losing enteropathy, with consequent hypoproteinemia and ascites. Appetite is variable; polyphagia may be present in the face of significant weight loss, whereas anorexia occurs with severe inflammation. Milder inflammation may not affect appetite, although postprandial pain can be significant even without other signs. Systemic consequences of inflammatory bowel disease can occur, although reports are sparse.

Etiology and Pathogenesis

The underlying etiology of small animal inflammatory bowel disease is unknown, and comparisons have been made with similar human conditions. In this regard, the breakdown of immunologic tolerance to luminal antigens (bacteria and dietary components) is thought to be critical, perhaps resulting from disruption of the mucosal barrier, dysregulation of the immune system, or disturbances in the intestinal microflora. Therefore antigens derived from the endogenous microflora are likely to be important in disease pathogenesis, and a potential role for diet-related factors is suggested by the clinical benefit of dietary therapy in some cases of canine inflammatory bowel disease.

Genetic factors are likely to contribute to the pathogenesis of inflammatory bowel disease, and in humans the strongest associations are with genes of the human MHC (human leukocyte antigen [HLA]). Furthermore, some human patients with Crohn’s disease have a mutation in the NOD2 gene on chromosome 16. This gene’s product detects bacterial lipopolysac-charide and can activate the proinflammatory transcription factor NF-kB. Such a link may explain the development of aberrant immune responses to bacteria in certain individuals. Genetic factors are also likely in dogs, given the recognized breed predispositions, although studies are lacking

Diagnosis

Intestinal biopsy is necessary for a definitive diagnosis of inflammatory bowel disease, although the clinical signs and physical findings may be suggestive (see Box Clinical Signs Associated with Inflammatory Bowel Disease). The term idiopathic inflammatory bowel disease is limited to cases in which histologic evidence of inflammation is found without an obvious underlying cause. All other etiologies, including infectious, diet-responsive, and antibacterial-responsive conditions, should be excluded. Therefore before intestinal biopsy is undertaken, laboratory evaluation and diagnostic imaging are performed. Such tests cannot provide a definitive diagnosis of inflammatory bowel disease, but they can help eliminate the possibility of anatomic intestinal disease (e. g., tumor, intussusception), extraintestinal disease (e. g., pancreatitis), and known causes of intestinal inflammation. Furthermore, by determining whether focal or diffuse intestinal disease is present, the clinician can choose the most appropriate method of intestinal biopsy.

Hematology Occasionally neutrophilia, with or without a left shift, is noted. Eosinophilia may suggest EGE, but it is neither pathognomonic nor invariably present. Anemia may reflect chronic inflammation or chronic blood loss.

Serum biochemistry No pathognomonic changes are seen in 1BD, but diseases of other organ systems should be recognized and excluded. Hypoalbuminemia and hypoglobulinemia” are characteristic of protein-losing enteropathy, whereas hypocholesterolemia may suggest malabsorption. Intestinal inflammation in dogs may cause a “reactive hepatopathy, ” with mild elevations in liver enzymes (alanine aminotransferase (ALT] and alkaline phosphatase [ALP]). In contrast, because of the shorter half-lives of liver enzymes in cats, increases are more likely to be the result of hepatocellular or cholestatic disease.

Fecal examination Fecal examination is most important for eliminating other causes of mucosal inflammation, such as nematodes (e. g., Trichuris, Uncinaria, Ancylostoma, and Strongyloides spp.), Giardia infection, and bacterial infection (e. g., Salmonella or Campylobacter spp. or clostridia). Given that fecal parasitology may not always detect Giardia organisms, empirical treatment with fenbendazole is recommended in all cases.

Increased fecal alphap1-PI concentrations would be expected in dogs with inflammatory bowel disease, as well as significant intestinal protein loss even before hypoproteinemia develops (see above).

Folate and cobalamin Serum concentrations of both these vitamins are affected by intestinal absorption, therefore proximal, distal, or diffuse inflammation can result in subnormal folate concentrations (proximal inflammation) or cobalamin concentrations (distal inflammation) or both (diffuse inflammation). Although such alterations are not pathognomonic for inflammatory bowel disease, deficiencies may require therapeutic correction. Measurement of serum folate and cobalamin is now commercially available for cats, and cobalamin deficiency associated with inflammatory bowel disease has been documented. Cobalamin deficiency has systemic metabolic consequences, and anecdotal evidence suggests that deficient cats with inflammatory bowel disease require parenteral supplementation to respond optimally to immunosuppression.

Diagnostic imaging Imaging studies document whether focal or diffuse disease is present and whether other abdominal organs are affected. Such information, in conjunction with specific clinical signs, allows the clinician to choose the most appropriate method of biopsy. Plain radiographs may be useful for detecting anatomic intestinal disease; contrast studies rarely add further information. Ultrasonographic examination is superior to radiography for documenting focal anatomic intestinal disease and is particularly useful in cats with inflammatory bowel disease. Ultrasonography permits evaluation of intestinal wall thickness and can document mesenteric lymphadenopathy. Ultrasound-guided fine needle aspiration (FNA) can provide samples for cytologic analysis, which may aid in diagnosis.

Intestinal biopsy Intestinal biopsy is necessary to document intestinal inflammation. Endoscopy is the easiest method of biopsy, but it has limitations, because samples are superficial and in m6st cases can be collected only from the proximal small intestine. In some cases exploratory laparotomy and full-thickness biopsy are necessary, although the procedures are more invasive and can be problematic if severe hypoproteinemia is present. These techniques may be more suitable for cats, given the tendency in this species for multiorgan involvement.

Histopathologic assessment of biopsy material remains the gold standard for inflammatory bowel disease diagnosis, and the pattern of histopathologic change depends on the type of inflammatory bowel disease present. However, the limitations of histopathologic interpretation of intestinal biopsies are recognized. The quality of specimens can vary, agreement between pathologists is poor, and differentiation between normal specimens and those showing inflammatory bowel disease and even lymphoma can be difficult. Grading schemes for the histopathologic diagnosis of inflammatory bowel disease have been suggested, but these have not yet been widely adopted.

IBD activity index In humans, activity indices are used to quantify the severity of inflammatory bowel disease; this helps practitioners to assess the response to treatment and to make a prognosis by allowing comparisons between published studies in the literature. Recently an activity index was suggested for canine inflammatory bowel disease, and this may aid disease classification in the future.

Other diagnostic investigations Given the limitations of histopathology, other modalities are required. One approach would be the use of immunohistochemistry or flow cytometry to analyze immune cell subsets. However, such techniques are labor intensive and poorly standardized and are unlikely to be generally available in the foreseeable future.

Treatment

Whatever the type of inflammatory bowel disease, treatment usually involves a combination of dietary modification and antibacterial and immunosuppressive therapy. Unfortunately, objective information on efficacy is lacking, and most recommendations are based on individual experience. The authors usually recommend a staged approach to therapy whenever possible; initial treatment involves antiparasiticides to eliminate the possibility of occult endoparasite infestation. Thereafter, sequential treatment trials with an exclusion diet and anlibacterials are pursued; immunosuppressive medication is used only as a last resort. However, in some cases, clinical signs or mucosal inflammation is so severe that early intervention with immunosuppressive medication is essential. If clinical signs are intermittent, the owners should keep a diary to provide objective information as to whether treatments produce genuine improvement.

Dietary modification The diets recommended for patients with inflammatory bowel disease are antigen limited, based on a highly digestible, single-source protein preparation. An exclusion diet trial should be undertaken to eliminate the possibility of an adverse food reaction, and most clients are happy to try this, given concerns over the side effects of immunosuppressive drugs. An easily digestible diet decreases the intestinal antigenic load and thus reduces mucosal inflammation. Such diets may also help resolve any secondary sensitivities to dietary components that may have arisen from disruption of the mucosal barrier. After the inflammation has resolved, the usual diet often can be reintroduced without fear of an acquired sensitivity.

Well-cooked rice is the preferred carbohydrate source because of its high digestibility, but potato, corn starch, and tapioca are also gluten free. Fat restriction reduces clinical signs associated with fat malabsorption. Modification of the n3 to n6 fatty acid ratio may also modulate the inflammatory response and may have some benefit both in treatment and in maintenance of remission, as in human inflammatory bowel disease. However, no direct studies have been done to prove a benefit in canine inflammatory bowel disease. Supplementation with oral folate and parenteral cobal-amin is indicated if serum concentrations are subnormal.

Antibacterial therapy Treatment with antimicrobials can be justified in inflammatory bowel disease, partly to treat secondary small intestinal bacterial overgrowth and partly because of the importance of bacterial antigens in the pathogenesis of inflammatory bowel disease. Ciprofloxacin and metronidazole are often used in human inflammatory bowel disease, and metronidazole is the preferred drug for small animals. The efficacy of metronidazole may not be related just to its antibacterial activity, because it may exert immunomodulatory effects on cell-mediated » immunity. Furthermore, other antibacterials (e. g., tylosin) may also have immunomodulatory effects and have efficacy in canine inflammatory bowel disease.

Immunosuppressive drugs The most important treatment modality in idiopathic inflammatory bowel disease is immunosuppression, although this should be used only as a last resort. In human inflammatory bowel disease, glucocorticoids and thiopurines (e. g., azathioprine, 6-mercaptopurine) are used most widely. In dogs, glucocorticoids are used most frequendy, and prednisone and prednisolone are the drugs of choice. Dexamethasone should be avoided, because it may have deleterious effects on enterocytes. In severe inflammatory bowel disease, prednisolone can be administered parenterally, because oral absorption may be poor. The initial dosage of 1 to 2 mg / kg given orally every 12 hours is given for 2 to 4 weeks and then tapered slowly over the subsequent weeks to months. In some cases therapy can be either completely withdrawn or at least reduced to a low maintenance dose given every 48 hours.

Signs of iatrogenic hyperadrenocorticism are common when the highest glucocorticoid dose is administered. However, signs are transient and resolve as the dosage is reduced. If clinical signs of inflammatory bowel disease consistently recur when the dosage is reduced, other drugs can be added to provide a steroid-sparing effect. Budesonide, an enteric-coated, locally active steroid that is destroyed 90% first-pass through the liver, has been successful in maintaining remission in human inflammatory bowel disease with minimal hypothalamic-pituitary-adrenal suppression. A preliminary study showed apparent efficacy in dogs and cats, but limited information is available on the use of this drug.

In dogs, azathioprine (2 mg / kg given orally every 24 hours) is commonly used in combination with prednisone / prednisolone when the initial response to therapy is poor or when glucocorticoid side effects are marked. However, azathioprine may have a delayed onset of activity (up to 3 weeks) and, given its myelosuppressive potential, regular monitoring of the hemogram is necessary. Azathioprine is not recommended for cats; chlorambucil (2 to 6 rag / m given orally every 24 hours until remission, followed by drug tapering) is a suitable alternative. Other immunosuppressive drugs are methotrexate, cyclophosphamide, and cyclosporine. Methotrexate is effective in the treatment of human Crohn’s disease, but it is not widely used in companion animals; it often causes diarrhea in dogs. Cyclophosphamide has few advantages over azathioprine and is rarely used. However, cyclosporine may show promise for the future, given its T lymphocyte-specific effects and efficacy in canine anal furunculosis. Unfortunately, it is expensive, and studies in human inflammatory bowel disease have shown variable efficacy and toxicity.

Novel therapies for inflammatory bowel disease Novel therapies are increasingly used for human inflammatory bowel disease in an attempt to target more accurately the underlying pathogenetic mechanisms. These therapies include new immunosuppressive drugs, monoclonal antibody therapy, cytokines and transcription factors, and dietary manipulation (Table Novel Therapies for Human Inflammatory Bowel Disease). In the future, such therapies may be adopted for small animal inflammatory bowel disease.

Novel Therapies for Human Inflammatory Bowel Disease

Therapy Mechanism Of Action
Drug Therapy
Tacrolimus Immunosuppressant macrolide
Mycophenolate Inhibits lymphocyte proliferation; reduces IFN-gamma production
Leukotriene antagonists (zileuton, verapamil) Inhibit arachidonic acid cascade
Prostaglandin (PG) targeting agents Mucosal protection from PC analogs; anti-inflammatory effects from PC antagonists
Thromboxane synthesis inhibitors Anti-inflammatory effects
Ridogrel
Picotamide
Oxpentifylline Inhibits TNF-αlpha expression
Thalidomide Inhibits TNF-αlpha and IL-12 expression; reduces leukocyte migration; impairs angiogenesis
Bone Marrow and Stem Cell Transplantation
Bone marrow grafts Unknown; immunomodulation (?)
Dietary Manipulation
Protein hydrolysate diets “Hypoallergenic”
Fish oil therapy Diverts eicosanoid metabolism to LTB5 and PGE3
Short chain fatty acid therapy
Butyrate Provides nutrition for enterocytes
Probiotics and prebiotics Antagonize pathogenic bacteria; immunomodulatory effects
Cytokine Manipulation
Systemic IL-10 Down-modulatory cytokine
Anti-IL-2 monoclonal antibody (MAb) Counteracts proinflammatory effects
Anti-IL-2R (CD25) MAb Inhibits IL-2 effects
Anti-IL-12 MAb Counteracts proinflammatory effects
Anti-IL-11 MAb Downregulates TNF-alpha and IL-1beta
Recombinant IFN-alpha Anti-inflammatory; antiviral (?)
Anti-IFN-gamma MAb Immunomodulatory effect on Th 1 cells
Anti-TNF-αlpha MAb Counteracts proinflammatory effects; induces inflammatory cell apoptosis
Endothelial Cell Adhesion Molecules and Their Manipulation
ICAM-1 (antisense oligonucleotide) Reduces immune cell trafficking
Anti-alpha4 / beta7 MAb Reduces immune cell trafficking
Other Immune System Modulations
Intravenous immunoglobulin Saturates Fc receptors; other (?)
T-cell apheresis Immunomodulation
Anti-CD4 antibodies Immunomodulation
Transcription Factors
NF-kB antisense oligonucleotide Inhibits proinflammatory cytokine expression
ICAM-1 antisense oligonucleotide Reduces immune cell trafficking

IFN, interferon; IL, interleukin; ICAM, intercellular adhesion molecule; LTB, leukotriene B; MAb, monoclonal antibody; PG, prostaglandin; PGE, prostaglandin E; Th 1, T helper 1; TNF, tumor necrosis factor

Mycophenolate mofetil recently has been used to treat human inflammatory bowel disease, although its efficacy is variable. Drugs that target TNF-α (e. g., thalidomide and oxpentifylline) may be suitable for the treatment of canine inflammatory bowel disease because of the importance of this cytokine in disease pathogenesis. Human open-label trials have demonstrated a beneficial effect for thalidomide in refractory Crohn’s disease. Oxpentifylline has shown efficacy in studies in vitro, but clinical results have been less rewarding. Anti-TNF-alpha monoclonal antibody therapy, which has also undergone trials in human inflammatory bowel disease, has the additional beneficial effect of inducing apoptosis in inflammatory cells. Species-specific monoclonal antibodies will be needed for canine and feline inflammatory bowel disease.

Finally, modulation of the enteric flora with probiotics or prebiotics may have benefits in targeting the pathogenesis of inflammatory bowel disease. A probiotic is an orally administered living organism that exerts health benefits beyond those of basic nutrition. In addition to having direct antagonistic properties against pathogenic bacteria, they modulate mucosal immune responses by stimulating either innate (e. g., phagocytic activity) or specific ( e. g., secretory IgA) immune responses. However, care should be taken to select the most appropriate organisms, which are likely to vary between host species.

Prebiotics are selective substrates used by a limited number of “beneficial” species, which therefore cause alterations in the luminal microflora. The most frequently used prebiotics are nondigestible carbohydrates, such as lactulose, inulin, and FOS. Both probiotics and prebiotics can reduce intestinal inflammation in mouse models of inflammatory bowel disease. Preliminary placebo-controlled trials with probiotics and prebiotics in human inflammatory bowel disease patients have shown promising results, although similar trials in canine and feline inflammatory bowel disease are still awaited.

Lymphocytic-Plasmacytic Enteritis

Basenji Enteropathy

A severe, hereditary form of lymphocytic-plasmacytic enteritis has been well characterized in basenjis, although the mode of inheritance is unclear. It has been likened to immunoproliferative small intestinal disease (IPSID) in humans, because both conditions involve intense intestinal inflammation. However, IPSID is characterized by an associated gammopathy (alpha heavy chain disease) and a predisposition to lymphoma. Affected basenjis often have hyper-globulinemia but not alpha heavy chain disease and may be predisposed to lymphoma. The intestinal lesions in basenjis are characterized by increases in CD4+ and CD8+T cells.

Clinical Signs

Signs of chronic intractable diarrhea and emaciation are most rommon Lymphocytic-plasmacytic paslritis, with hypergasirmemia and mucosal hyperplasia, may be seen in addition to the enteropathy. Protein-losing enteropathy often occurs, with consequent hypoalbuminemia, although edema and ascites are not common. Clinical signs are usually progressive, and spontaneous intestinal perforation may occur.

Diagnosis

The approach to diagnosis is the same as before, and ultimately depends on histopathological examination of biopsy specimens.

Treatment

Treatment generally is unsuccessful, with dogs dying within months of diagnosis. However, early, aggressive combination treatment with prednisolone, antibiotics, and dietary modification may achieve remission in some cases.

Familial Protein-Losing Enteropathy and Protein-Losing Nephropathy in Soft-Coated Wheaten Terriers

Recendy a clinical syndrome unique to soft-coated wheaten terriers was characterized. Affected dogs present with signs of protein-losing enteropathy or PLN or both. A genetic basis is likely, and although the mode of inheritance is not yet clear, pedigree analysis of 188 dogs has demonstrated a common male ancestor. The disease is probably immune mediated, given the presence of inflammatory cell infiltration. A potential role for food hypersensitivity has been suggested, because affected dogs have demonstrated adverse reactions during provocative food trials and alterations in antigen-specific fecal IgE concentrations.

Clinical Signs

Signs of protein-losing enteropathy tend to develop at a younger age than PLN. Clinical signs of the protein-losing enteropathy include vomiting, diarrhea, weight loss, and pleural and peritoneal effusions. Occasionally, thromboembolic disease may occur.

Diagnosis

Preliminary laboratory investigations, as in most dogs with protein-losing enteropathy, demonstrate panhypoproteinemia and hypocholesterolemia. In contrast, hypoalbuminemia, hypercholesterolemia, proteinuria, and ultimately azotemia are seen with PLN, Histopathologic examination of intestinal biopsy material reveals evidence of intestinal inflammation, villus blunting, and epithelial erosions, as well as dilated lymphatics and lipogranulomatous lymphangitis.

Treatment and Prognosis

The treatment for protein-losing enteropathy is similar to that described for general inflammatory bowel disease, but the prognosis is usually poor.

Eosinophilic Enteritis

Other Forms of Inflammatory Bowel Disease

Granulomatous Enteritis

Granulomatous enteritis is a rare form of inflammatory bowel disease characterized by mucosai infiltration with macrophages, resulting in the formation of granulomas. The distribution of inflammation can be patchy. This condition is probably the same as “regional enteritis,” in which ileal granulomas have been reported. Granulomatous enteritis has some histologic features in common with human Crohn’s disease, but obstruction, abscessation, and fistula formation are not noted. Conventional therapy is not usually effective, and the prognosis is guarded, although a combination of surgical resection and anti-inflammatory treatment was reported to be successful in one case. In cats, a pyogranulomatous transmurai inflammation has been associated with FIPV infection.

Proliferative Enteritis

Proliferative enteritis is characterized by segmental mucosal hypertrophy of the intestine. Although many species can be affected, the condition is most common in pigs. A similar but rare condition has been reported in dogs. There have been suggestions of an underlying infectious etiology, and Lawsonia intracellularis has been implicated, although this has not yet been proved. Other infectious agents with a proposed link are Campylobacter spp. and Chlamydia organisms