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Abstract
The enterotoxaemia syndrome in Belgian Blue calves is characterised by a high case
fatality rate, sudden death, lesions of haemorrhagic enteritis of the 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 identification, the aerobic and anaerobic intestinal
flora of a population of 78 calves, originating from farms located in southern Belgium
and that died in circumstances defined as "calf enterotoxaemia" (study population)
and of 64 calves that died in other circumstances (control population) were studied
qualitatively 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 units (CFU) versus 10(4)-10(5)
CFU per ml of intestinal content) and from more animals (79 versus 19%) in the study
population than in the control population, although individual results from both populations
could overlap. Other clostridial species, i.e. mainly urease-negative C. sordellii
and C. bifermentans, were isolated in high numbers (>10(6) CFU per ml of intestinal
content) 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-negative anaerobes were not isolated
in high numbers from any of the samples. Aerobically beta-haemolytic E. coli were
significantly more frequent among the study population, but were isolated from only
25% of the animals. Salmonella Typhimurium was isolated from only two animals in the
study population. Less than 1% of the E. coli isolated were verotoxigenic and one-third
were necrotoxigenic. At this stage only non-enterotoxigenic type A C. perfringens
are thus statistically associated with the enterotoxaemia syndrome in Belgian Blue
calves and fulfil the first of the Koch's postulates.