Escherichia coli, formerly known as Bacillus coli, is a normal inhabitant of the alimentary canal in most mammals. This bacterial family is a large one, comprising many differing serotypes which can be differentiated in the laboratory by means of the agglutination test. Only a few serotypes cause disease. However, E. coli infections can be severe and have become sufficiently prevalent for a range of vaccines to be developed for protection against the most common pathological strains in farm animals. (See also DIARRHOEA; JOINT-ILL; COLIFORM INFECTIONS.)
Escherichia coli scours and septicaemia are common in newborn lambs and often fatal. Vaccines are available for protection and antis-era may be used for treatment.
One serotype gives rise to oedema of the bowel; another to the death of piglets within a few days of birth.
Those strains of Escherichia coli which cause diarrhoea in piglets only a few days old are able to do so because they are covered with an adhesive coat known as the K88 antigen. This enables them to adhere to the wall of the intestine where they induce disease by means of toxins, causing diarrhoea, dehydration, and death.
Escherichia coli toxins are classified as (a) heat labile (LT), which may cause severe diarrhoea, dehydration and death of piglets; and (b) heat stable (ST) associated with only a mild enteritis.
Scouring in older pigs may often be caused by strains of E. coli having no K88 antigen.
The K88 antigen and related antigens can be prepared in the form of a vaccine, formulated with E. coli toxoids. This is injected into pregnant sows and gilts to provide protection (passive immunity) to the piglets when they are suckled, via the colostrum, by preventing the K88-coated E. coli from adhering to the intestinal wall. Oral and parenteral vaccines are available.
Escherichia coli is an important cause of calf enteritis, enterotoxaemia and septicaemia, and of mastitis. Combined antiserum preparations, vaccines, and antisera-vaccine combinations are available.
Coliform septicaemia is a frequent cause of loss, and one difficult to control since infected birds are disinclined to eat or drink, which hinders drug administration.
Escherichia coli is perhaps the most important pathogen of the bladder and urethra; it also causes enteritis.
(see DISEASES OF FOALS)
A strain of Escherichia coli, 0157, has been associated with outbreaks of disease in humans. Animals that carry this toxic strain do not usually show any signs of clinical disease and shedding of the organism by animals is erratic, making detection difficult. Young children and the elderly are most susceptible to the disease. In the mild form there is blood-tinged diarrhoea. Some of those cases will go on to develop haemorrhagic diarrhoea and a number develop neurological disease that is fatal. Following an outbreak involving more than 50 persons who had eaten contaminated meat, an investigation led by Professor Hugh Pennington of Aberdeen University resulted in a series of recommendations for good hygiene practices.