Avian Eimeria: Effects of Gamma Irradiation on Development of Cross-Species Immunity in Foreign and Natural Host Birds

Abstract

Repeated inoculation (immunization) of white leghorn chickens with oocysts of the turkey coccidium, Eimeria adenoeides, resulted in significantly improved weight gain and feed-conversion ratios (feed efficiency) after E. tenella challenge. However, the development E. tenella in the immunized chickens did not differ markedly from that in unimmunized chickens, and intestinal lesions remained severe (greater than 3.0). Apparently improved weight gain and feed efficiency can be maintained in the presence of extensive parasite development. The ability to elicit cross-protective immunity was abrogated when the E. adenoeides oocysts were exposed to 15 kRad of gamma irradiation before inoculation into the chickens. Sporozoites existing from irradiated oocysts of E. acervulina also failed to immunize the chickens against challenge with E. tenella but protected chickens almost completely against homologous challenge with E. acervulina. The results indicate that cross-species immunity is not elicited by all developmentally arrested sporozoites and that the ability to produce cross-species immunity can be destroyed by gamma irradiation of the immunizing species.

Vaccines against the avian enteropathogensEimeria,CryptosporidiumandSalmonella

“…Jenkins et al (1991a) used X-irradiated oocysts of E. acervulina to produce a vaccine conferring resistance against coccidiosis and suggested that protective immune responses of the host occurred during an early critical period in intracellular development. Repeated inoculation with ␥-irradiated turkey coccidium (E. adenoides) into chickens resulted in significantly improved weight gain and feed efficiency after challenge with E. tenella (Augustine et al, 1993). In this foreign host, E. adenoides sporozoites excysted and invaded the intestinal epithelium but underwent little or no further development.…”