Protection against Coccidiosis in Outbred Chickens Elicited by Gamma-Irradiated Eimeria maxima

Abstract

In an effort to develop an attenuated coccidiosis vaccine against coccidiosis, we exposed Eimeria maxima oocysts to an optimum dose of gamma irradiation (17 kRad) that does not affect sporozoite invasion of the intestinal mucosa but does prevent asexual parasite development. Irradiated E. maxima oocysts were suspended in gelatin slabs and placed in battery cages for ingestion by 1-day-old chickens. Separate groups of chickens were given gelatin slabs containing nonirradiated E. maxima oocysts or were inoculated per os with either irradiated or nonirradiated E. maxima oocysts. Chickens infected with irradiated or nonirradiated oocysts by either oral inoculation or gel delivery showed a dose-dependent protection against weight loss associated with E. maxima challenge compared with unimmunized controls. In general, nonirradiated oocysts elicited protective immunity at lower immunization doses compared with irradiated oocysts. These experiments were extended to a floor pen study wherein 1-day-old male and female broiler chickens were given irradiated or nonirradiated E. maxima oocysts in gelatin slabs in hatching boxes and challenged at 4 wk of age. A significant reduction (P < 0.05) in lesion scores was observed for chickens immunized with either irradiated or nonirradiated oocysts compared with unimmunized controls. Although no significant difference (P > 0.05) 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 with those animals immunized with nonirradiated oocysts.

The Relationship Between the Anticoccidial Effects of Clindamycin and the Development of Immunity in the Eimeria pragensis/Mouse Model of Large Intestinal Coccidiosis

“…As described above, the previously published data suggest that various developmental stages of parasite can induce substantial immunity. Interestingly, the previous study indicated that larger doses of irradiated E. maxima were required to induce immunity in chickens and suggested that dose of antigen might be important, where the important protection-inducing antigen would affect in the successive developmental stages [11]. Our data allow to put a similar interpretation on E. pragensis but also suggests that the proportions of different developmental stages of parasite may not dramatically influence the development of immunity.…”

IL‐12 Knockout C57BL/6 Mice are Protected from Re‐infection with Cryptosporidium parvum after Challenge

“…Effects of gamma irradiation have been studied with Eimeria maxima in an effort to develop an attenuated coccidiosis vaccine [8,10] and also with C. parvum oocyst viability to assess its effectiveness in the prevention of C. parvum infection [15]. In our study, to confirm that the immunity observed in IL‐12 knockout mice challenged with C. parvum oocyst was due to the primary oocyst infection, we exposed C. parvum oocysts to similar doses of y‐irradiation used for E. maxima that have been shown to affect sporozoite invasion of the intestinal mucosa but does prevent asexual parasite development following irradiation (17 kRad).…”

The influence of immunizing dose size and schedule on immunity to subsequent challenge with antigenically distinct strains ofEimeria maxima

“…[2001] and Williams [2001], respectively; supported by this study). The influence of the initial dose size or number on immune protection against subsequent homologous challenge with Eimeria acervulina , Eimeria brunetti , E. maxima or Eimeria tenella infection has been described (Hein, 1975;Lillehoj, 1988;Jenkins et al ., 1997) but remains less clearly defined in the face of challenge by a heterologous strain (Smith et al ., 2002). That initial doses of five or 10 oocysts of E. maxima proved capable of inducing a high degree of immunity to homologous challenge supports previous reports of the potent immunogenicity of this parasite (Rose & Long, 1962;Lee & Fernando, 1978;Smith et al ., 2002).…”