Bacterial intestinal flora associated with enterotoxaemia in Belgian Blue calves

The enterotoxaemia syndrome in Belgian Blue calves is characterised by a hi gh case fatality rate, sudden death, lesions of haemorrhagic enteritis of t he small intestine and, quite often an absence of other clinical signs but its cause has not been yet identified. As a first step in this identificati on, the aerobic and anaerobic intestinal flora of a population of 78 calves , originating from farms located in southern Belgium and that died in circu mstances defined as "calf enterotoxaemia" (study population) and of 64 calv es that died in other circumstances (control population) were studied quali tatively and quantitatively. The colonies were identified after subcultures with appropriate API sugar sets. Anaerobically Clostridium perfringens was isolated in higher numbers (mean values of 10(7)-10(7.5) colony forming un its (CFU) versus 10(4)-10(5) CFU per mi of intestinal content) and from mor e animals (79 versus 19%) in the study population than in the control popul ation, although individual results from both populations could overlap. Oth er clostridial species, i.e. mainly urease-negative C. sordellii and C, bif ermentans, were isolated in high numbers (>10(6) CFU per mi of intestinal c ontent) from a few animals in the study population only. All but one of the 705 C. perfringens isolates from both populations belonged to the A toxin type and none of the urease-negative C. sordellii was toxigenic. Gram-negat ive anaerobes were not isolated in high numbers from any of the samples. Ae robically beta -haemolytic E. coli were significantly more frequent among t he study population, but were isolated from only 25% of the animals. Salmon ella Typhimurium was isolated from only two animals in the study population . Less than 1% of the E. coli isolated were verotoxigenic and one-third wer e necrotoxigenic. At this stage only non-enterotoxigenic type A C. perfring ens are thus statistically associated with the enterotoxaemia syndrome in B elgian Blue calves and fulfil the first of the Koch's postulates. (C) 2001 Elsevier Science B.V. All rights reserved.