Abstract
The present paper describes the field evaluation of local gametocyte vaccine and its comparative efficacy with commercial anticoccidial vaccine, LivaCox (R), used in breeder and broiler flocks in Pakistan. Humoral immune response in vaccinated and control chickens was monitored by enzyme-linked immunosorbent assay. Results demonstrated significantly elevated antibody titres in vaccinated groups as compared to control groups conducted both in Laboratory and field experiments. Significantly (P < 0.01) higher antibody titres in local gametocyte-vaccinated group as compared to LivaCox (R)-vaccinated chickens were recorded. Splenic cell migration inhibition assay was used to detect the cell-mediated immune (CMI) response, and results were expressed in terms of per cent migration index. Lower per cent migration index in LivaCox (R)-vaccinated chickens indicated the higher CMI response, as compared to local gametocyte-vaccinated chickens, although the difference was statistically non-significant (P > 0.05). Results of the challenge studies in laboratory experiments revealed significantly higher (P < 0.05) oocyst count in LivaCox (R)-vaccinated group as compared to local gametocyte-vaccinated chickens. Maximum protection (75%) against mixed species of genus Eimeria was recorded in chickens vaccinated with gametocyte vaccines as compared to LivaCox (R)-vaccinated group. The mean body weight gains in chickens vaccinated with local gametocyte vaccine were significantly better (P < 0.05) than in chickens vaccinated with LivaCox (R) vaccine, both in laboratory and field experiments. Majority of the chickens (70-72%) in control group demonstrated severe lesions (3.0-4.0), while 20-26% chickens showed moderate lesions (2.0). On the other hand, local gametocyte- and LivaCox (R) immunized chickens developed 78% and 85% mild to moderated lesions (1.0-2.0), respectively. Results of the present study provide a probable explanation for cross-protection induced by Eimeria tenella gametocyte vaccines against other species of genus Eimeria.