Evaluation of Sonicated Oocyst Vaccine in Protection Against Hepatic Coccidiosis in Rabbits

Background: Hepatic coccidiosis, caused by Eimeria stiedae, is considered to be a devastating disease for rabbit colonies resulting in high morbidity and mortality. Many anticoccidial drugs became less effective against this microorganism, and there is urgent need for appropriate alternative for these compounds. Aims: this study aimed to evaluated the protective efficacy of sonicated E. stiedae sporulated oocyst against the experimental infection with this parasite. Materials and Methods: A total of 18 rabbits were divided into three equal groups: the first (G1) and second group (G2) were vaccinated s/c with 1 ml and 0.5 ml respectively of sonicated E. stiedae sporulated oocyst, while the third group (G3) represented positive control group. Challenge with 1000 oocyst/animal (orally) was performed on the 20th day after vaccination. Oocyst per gram of feces (OPG) was counted on day 17, 20, 23, 26, 29 and 32 post challenge (PC). Blood samples were obtained from each rabbit on 14, 20, 28, 42, 56 and 70 after immunization. Passive haemagglutination (PHA) test was used to estimate antibody titer. All rabbits were weighted on 1, 14, 28, 42, 56 and 70 day post vaccination. Results: There were highly significant differences in oocyst shedding between the vaccinated groups (G1 and G2) and non vaccinated group (G2) from the first day of oocyst shedding till the day 32 PC, while there were no significant differences between G1 and G2 although G2 had higher oocyst shedding rate. The same significant differences were recorded regarding Ab titers after 14 days of vaccination until the end of the study. Calculated weight gain revealed that G1 and G2 had very close weight gains (196 gm, 180 g and 199 gm respectively) compared to only 57 gm for G3. Conclusion: This vaccine can give partial protection against infection with E. steidae in rabbits. Such vaccine can be subjected to further study to improve its efficiency in order to be a suitable alternative for anticoccidial drugs.