Evaluating the role of vaccination and oocyst management in modulating immune responses of Eimeria-challenged turkey poults.

This study aimed to assess the effects of Eimeria vaccination and amprolium treatment on growth performance, fecal oocyst shedding, and immune response in tom poults challenged with mixed Eimeria species. Two experiments were completed; experiment 1 evaluated the effect of vaccine and amprolium (A) supplementation on OPG cycling. Poults were assigned to five groups: (a) non-vaccinated, non-inoculated (NVNI), (b) low dose (L), (c) low dose with A (LA), (d) high dose (H), and (e) high dose with A (HA). On d1, 40% of poults in the L & LA groups were vaccinated with 100 oocysts/poult of mixed Eimeria species, while 70% in the H & HA group were vaccinated with 500 oocysts/poult. Experiment 2 involved poults randomly assigned to three groups: (a) non -vaccinated (NV), (b) vaccinated (V), and (c) vaccinated plus A (VA). In the V and VA groups, 40% of poults received 100 oocysts/poult containing mixed Eimeria species on d1, while VA received amprolium from d8 to d12. On d21, V and VA were challenged with 25,000 oocysts/poult of Eimeria. Fecal oocyst shedding was monitored from d6 to d28 and lesion scores on d28. Immune responses were assessed by mRNA expression analysis in the ceca and cecal tonsils, and immune cell profiling in the cecal tonsils. L had the highest oocyst shedding, followed by H. In both experiments, lesion scores were minimal and fecal oocyst shedding was significantly reduced (P < 0.05) in the treatment groups receiving brief amprolium. Immune modulation was most pronounced in the VA group, showing that low oocyst cycling can still induce an immune response in turkeys. Overall, combining vaccination with amprolium improved performance, reduced oocyst shedding, and mitigated intestinal damage while modulating the immune response, thereby offering an effective strategy for managing coccidiosis vaccine response in poultry.