Enterotoxigenic Escherichia coli (ETEC) in farm animals

Animal diseases due to enterotoxigenic Escherichia coli (ETEC) typically ap pear as severe watery diarrhoea during the first few days of life (also a f ew days after weaning in pigs). ETEC adhere to the small intestinal microvi lli without inducing morphological lesions and produce enterotoxins acting locally on enterocytes. This action results in the hypersecretion (of water and electrolytes) and reduced absorption. Adhesins and toxins are the two prominent virulence attributes of ETEC and the level of knowledge of these factors determines the chances for successful prevention and therapy of the disease. For animal ETEC the most common adhesins are the fimbriae (pili) on the surface: F4(K88), F5(K99), F6(987P), F41, F42, F165, F17 and F18. En terotoxins (extracellular proteins or peptides) of animal ETEC are classifi ed as heat-labile (LT) and heat-stable (ST) enterotoxins with further subdi visions (LTh-I, LTp-I, LTIIa, LTIIb, STaH, STaP, STb) according to antigeni c and biological differences. Fimbriae and LT enterotoxins are made up of l arge molecular weight proteins which facilitate their utilisation in vaccin es and their detection using immunodiagnostic systems. The adhesive fimbria e and enterotoxins of animal ETEC are plasmid determined (except F41 and F1 7). Virulence gene probes (DNA hybridisation, PCR) are specific and sensiti ve diagnostic and epidemiologic tools for the detection of ETEC. Based on g enetic typing, the ETEC, in spite of limited serogroups, seem to represent a population of E. coli with a diverse genetic background. (C) Inra/Elsevie r, Paris.