Evaluation of Predisposing Factors of Necrotic Enteritis in Experimentally Challenged Broiler Chickens

SIMPLE SUMMARY: The ban of antibiotic growth promoters in animal feed increased the number of cases of necrotic enteritis (NE) in broilers, greatly affecting the poultry industry. The induction of experimental NE faces challenges, as it is a multifactorial disease and the pathogenesis is not fully understood, hampering the development of in vivo studies for disease control and prevention strategies. The literature reports several protocols using different factors to assist in NE induction. This study assessed predisposing factors, such as immunosuppression, infection or both, by Eimeria spp. in broilers (n = 99) fed a wheat-based diet and challenged with three different strains of Clostridium perfringens (CP). Under microscopy, Eimeria spp. had a negative effect on intestinal morphometry and favored the increase of intraepithelial lymphocytes. However, the macroscopic analysis did not show which factor was more effective in potentiating the lesions, suggesting a synergistic effect between the strain of CP used and the predisposing factors. Therefore, each experimental protocol should first be evaluated for the association of the CP strain with the predisposing factors. ABSTRACT: Clostridium perfringens is the etiological agent of NE, a disease that greatly affects the poultry industry. Experiments on the induction of NE are difficult to carry out, as it is a multifactorial disease, and thus different predisposing factors have been used. This study evaluated the effect of the Gumboro disease vaccine virus vaccine (IBDV-vac) associated or not with infection by Eimeria spp. in broilers, as a predisposing factor for NE. Broilers (n = 99) were divided into groups (11) challenged with IBDV-vac, Eimeria spp. CP type G (CP13, CP14 and CP03) or both. The macroscopic evaluation revealed that the highest average (3.45) of injury occurred for the CP13 + IBDV-vac group. The microscopic analysis showed that Eimeria spp. increased the population of intraepithelial lymphocytes and reduced the villus/crypt ratio in duodenum and jejunum when associated with CP13 or CP14. There was a synergistic effect between the CP strain used and the predisposing factors; nevertheless, it was not clear which was the most effective predisposing factor to potentiate the lesions, suggesting that the association of the strain with the factors should first be evaluated for each experimental protocol.