Pathoanatomical and blood biochemical investigations in chicks, challenged with Escherichia coli on the background of a pre-existing Eimeria infection.

SUMMARY Because of high frequencies of colibacillosis and coccidiosis in poultry and their eventual coexistence, this study was conducted for investigating plasma enzyme activities (ASAT, ALAT and ALP) in association with the severity of pathoanatomical findings in chickens with mono-infections (with E. coli or E. tenella only) or co-infection. For that, 160 broiler chickens were randomly divided into 4 equal groups according to the pathogen administration: birds from the group I (mono-infected) and from the group III (co-infected) were orally infected with 8.104 sporulated E. tenella oocysts when they were 12 days old and E. coli (serotype O78, 10 7 cfu) was intraperitoneally injected to chickens from the group II (mono-infected) and from the group III when they were 16 days old, whereas the group IV served as negative control group. Blood samples were collected and animals were slaughtered when they were 20 days old. Eimeria infected chickens exhibited haemorrhagic inflammatory lesions associated with dystrophic and necrotic processes principally in the caecum but also in liver and kidneys, in heart and in brain and cerebellum while in birds receiving E. coli, a fibrinous air-sacculitis, perihepatitis or pericarditis, and a gallbladder inflammation were also noticed and that in the case of mono-infection, caecum and brain lesions were absent. By contrast, all pathological findings were present and exacerbated in co-infected chickens. The plasma ASAT and ALAT activities were significantly increased in all infected chickens whereas ALP activities were significantly depressed in animals infected with E. coli. These changes were most prominent in birds co-infected. These results suggest that pre-invasion with E. tenella aggravates the colibacillosis and that this situation would be under-estimated in clinical practice.