Cause of Salmonella
Salmonella spp. are predominandy motile, gram-negative facultative anaerobic rod-shaped bacteria found in the feces of normal and diarrheic animals. As with many other commensal organisms of the gastrointestinal tract, the high prevalence of these organisms complicates diagnosis. From 1% to 30% of the fecal samples or rectal swabs taken from healthy domestic pet dogs, 16.7% of dogs boarded in kennels, and 21.5% of hospitalized dogs were found to be positive on bacteriologic culture for Salmonella. From 1% to 18% of healthy cats and 10.6% of random source research colony cats are also culture-positive for Salmonella. Despite these findings, several species of Salmonella have been impugned in the pathogenesis of acute enterocolitis in dogs and cats. S. typhimurium is the species most commonly isolated from diarrheic feces of dogs and cats, although other species have been identified.
Those most at risk for Salmonella infection are young and immunoincompetent animals, those with concurrent gastrointestinal infections (e. g., parvoviral or parasitic infections), and those animals who have had prior therapeutic interventions (e. g., antibiotics or glucocorticoids). Salmonella is an enteroinvasive organism that induces an acute inflammatory response resulting in enterocolitis, mucosal sloughing, and secretory diarrhea. Most Salmonella infections are resolved via the local immune response, but bacterial translocation and septicemia may evolve into systemic inflammatory response syndrome and multiple organ dysfunction syndromes (MODS) in some patients. Early recognition is important in preventing this sequela.
The main clinical signs of Salmonella enterocolitis are anorexia, lethargy, fever, vomiting, diarrhea with mucous and blood pigments, dehydration, abdominal pain, and tenesmus. With bacterial translocation and septicemia, affected animals may have evidence of pale mucous membranes, weakness, tachycardia, tachypnea, and vascular collapse.
Diagnosis of Salmonella
Culture, serotyping, and polymerase chain reaction are the best methods oi diagnosing Salmonella infections.
Treatment of Salmonella
Treatment varies according to the severity of the clinical signs. Mild, self-limiting forms of enterocolitis may in fact resolve with little more than supportive therapy. Antibiotic therapy in such cases may prolong fecal shedding and encourage development of the carrier state. In animals with severe hemorrhagic diarrhea, history of immunosuppression, suspected or documented septicemia, evidence of systemic inflammatory response syndrome, or a combination of these symptoms, parenteral antibiotics should definitely be used. If culture results are unavailable, therapy should include enrofloxacin, amoxicillin, or trimethoprim-sulfa, all of which are effective against Salmonella. Post-treatment cultures should be performed to confirm eradication, and pet owners should be advised of the public health importance of the disease.
Prognosis of Salmonella
The prognosis for recovery in nonsepticemic patients is generally good, although some animals may remain chronic carriers with recrudescence during periods of stress or unrelated disease. The prognosis for the septicemic patient is more guarded.