Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 5, 1997
Publication Date: N/A
Interpretive Summary: Avian coccidiosis is a parasitic disease caused by protozoa of the genus Eimeria. Until the introduction of anti-coccidial compounds for medicating feed, growth of the poultry industry was thwarted by this parasitic disease. Although broiler production in the U.S. and worldwide has grown steadily for 20 years, the repeated appearance of drug-resistant strains of coccidia has prompted the search for alternative methods of control. The present study, provides a possible alternative to drug treatment by using immunity to protect chickens against coccidiosis. Broiler chickens were inoculated with radiation-attenuated coccidia using a gelatin matrix as the delivery method. One-day-old chickens that ingested the vaccine preparation showed no signs of disease and were protected against a challenge infection with virulent coccidia. This study showed that vaccination is a viable alternative to drug treatment and may be applicable to current husbandry techniques in the poultry industry.
Technical Abstract: In an effort to develop an attenuated coccidiosis vaccine against coccidiosis, Eimeria maxima oocysts were exposed to an optimum dose of gamma irradiation (17 kRad) that does not affect sporozoite invasion of the intestinal mucosa but prevents further asexual parasite development. Irradiated E. maxima oocysts were suspended in gelatin slabs and placed in battery cages for ingestion by one-day-old chickens. Separate groups of chickens were given gelatin slabs containing non-irradiated E. maxima oocysts, or were inoculated per os with either irradiated or non-irradiated E. maxima oocysts. Chickens infected with irradiated or non-irradiated oocysts either by oral inoculation or gel delivery showed a dose-dependent protection against weight loss associated with E. maxima challenge compared to non-immunized controls. These experiments were extended to a floor pen study. A significant reduction (P < .05) in lesion scores was observed for chickens immunized with either irradiated or non-irradiated oocysts compared to unimmunized controls. Although no significant difference (P > .05) was observed in weight gain between these groups, both male and female chickens inoculated with irradiated E. maxima oocysts showed about a 10% greater weight gain than unimmunized controls. For both male and female chickens, average weights at challenge were greater in groups that were immunized with 17 kRad-irradiated E. maxima oocysts compared to those animals immunized with non-irradiated oocysts.