Evaluation of the Efficacy of a Field Isolate of <i>Eimeria</i> Oocysts Immunization in Two Breeds of Chickens - Demystifying use of Coccidiosis Vaccines

Abstract

Immunization efficacy of a field isolate of unattenuated sporulated Eimeria oocysts in broiler and Nigerian indigenous chickens (NIC) was investigated. Both breeds of birds were grouped and inoculated with varying dose levels (750, 1500 and 3000) of the oocysts per bird.  The immunizing infections were truncated with an anticoccidial drug following detection of patency evident by presence of Eimeria oocysts in the faeces of inoculated birds on day 4 of inoculation.  Immunized birds were then given challenged infections of 10,000 oocysts of the same Eimeria isolate per bird and an additional group that did not receive the immunizing infections was also challenged with 10,000 oocysts to serve as the unimmunized-challenged control while another group remained as uninfected-unchallenged control.  Immunized birds were found to be protected against the challenge infections evident by having significantly less severe gross lesion scores (0 to 1) in contrast to the unimmunized-challenged control birds (which had lesion scores of 2 to 4 and 1 to 2 in broiler and indigenous chickens respectively).  The infection was more severe in broiler chickens in contrast to the indigenous chickens judged by more severe lesion scores and significantly higher oocysts counts in the broilers.  Broilers also had significantly lower PCV (P < 0.05) in comparison to their indigenous counterparts.  Infected birds generally suffered infections more in contrast to the uninfected control birds judged by the significantly higher body weights and PCV of the uninfected birds (P < 0.05).  The results showed that the protection of birds against coccidiosis by immunization with the Eimeria isolate is feasible and this can therefore serve as a premise for the recommendation of immunization against coccidioisis in eastern Nigeria where the practice is extremely low or unknown by poultry farmers and hardly recommended to poultry producers by veterinarians and their allies in spite of the endemicty and severity of the disease in the area.  All the dose levels tried in this study were protective with no obvious differences between the dose levels and we recommended the use of 750 oocysts of such isolates to minimize the risk clinical coccidiosis. Local isolates of Eimeria would also have the added advantage in that they are likely to contain multiple Eimeria species that could provide full protection against the entire spectrum of Eimeria that occur in the area.