Quantification of gut lesions in a subclinical necrotic enteritis model
Résumé
Currently Clostridium perfringens induced necrotic enteritis is a major problem in broiler flocks. In the present study, broilers were inoculated with a combination of Eimeria maxima or overdose coccidial vaccine (one inoculation) with Clostridium perfringens (repeated inoculations). Single Clostridium perfringens, Eimeria maxima or overdose live coccidial vaccine inoculations did not result in grossly visible necrotic gut lesions, while combined inoculation resulted in typical necrotic lesions at approximately 4 days after inoculations with Clostridium perfringens in approximately half of the inoculated animals. Semi-quantitative histological lesion scoring was done to evaluate gut damage in gut sections of animals in which no gross necrotic lesions were detected. This included scoring of hyperemia, haemorrhages, the amount of red blood cells and protein precipitate in the lumen, villus fusion and epithelial defects. Villus length and villus length/crypt depth ratio were also analysed. This approach proved to be discriminative between single Eimeria maxima, overdose coccidial vaccine or Clostridium perfringens inoculations and the non-inoculated control group, and between the double and single inoculated groups. In general, highest histological scores for gut lesions were observed in the double inoculated groups, but the single inoculated groups had higher scores compared to the control group. It was concluded that oral inoculation of broilers with an overdose of live coccidial vaccine in combination with multiple oral Clostridium perfringens inoculations is a suitable model for necrotic enteritis without inducing mortality of the animals. Clostridium perfringens and Eimeria act synergistically in inducing grossly visible gut damage.
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