Selection and identification of a precocious line of Eimeria intestinalis with enlarged oocysts and deletion of one generation of schizogony
- 12 Downloads
Rabbit coccidiosis is a common parasitic disease and responsible for enormous economic losses in the rabbit industry. Eimeria intestinalis, one of the highly pathogenic and common Eimeria species infecting rabbits, is considered as an indispensable species for the development of live oocyst vaccines against rabbit coccidiosis. In this study, we report the successful selection of a precocious line (EIP8) from a wild-type strain of E. intestinalis (WT) by successively collecting and propagating the early excreted progeny oocysts. The EIP8 line had a prepatent period of only 132 h compared to 204 h for the WT. Oocysts of EIP8 were notably different from those produced by the WT strain by their significantly larger size (mean length: 29.3 vs 27.6 μm and mean width 20.5 vs 19.8 μm). Examination of tissue sections prepared from EIP8-infected rabbits revealed that this precocious line undergoes only two generations of schizogony before differentiating into gametocytes by 120 h post-infection. In contrast, WT parasites undergo three generations of schizogony and gametocytes are present by 168 h post-infection. EIP8 multiplication capacity reduced by more than 35-fold and a concomitant decrease in pathogenicity was detected. Interestingly, immunization with 103 or 104 EIP8 oocysts provided sufficient protection against homologous challenge with wild-type parasites, as body weight gain of immunized and challenged rabbits was similar to that of untreated animals, as well as more than 90% reduction of oocyst output was detected in immunized and challenged animals when compared to unimmunized and challenged animals. Together, these results show that the EIP8 precocious line of E. intestinalis is an attenuated immunogenic strain and a suitable candidate for the development of a live vaccine against rabbit coccidiosis.
KeywordsEimeria intestinalis Precocious line Morphology Endogenous development Pathogenicity Immunogenicity
This research was supported by China Agricultural Research System (CARS-43), the National Natural Science Foundation of China (31572507 and 31472180), and Chinese Ministry of Agriculture (948 Program: 20015-Z31).
Compliance with ethical standards
Experiments were approved by China Agricultural University Laboratory Animal Welfare and Animal Experimental Ethical Inspection Committee (CAU20160921-2). Animal experiments were carried out in accordance with Chinese National Laboratory Animal Standards (GB 14925-2010/XG1-2011). Enough food and water were provided. Handling of animals was minimal when they were inoculated and weighed. Fecal samplings were performed outside the rabbit cages. Rabbits were euthanized in a humane manner.
Conflict of interest
The authors declare that they have no conflict of interest.
- Coudert P, Licois D, Drouet-Viard F (1995) Eimeria species and strains of the rabbits. In: Eckert J, Braun R, Shirley MW and Coudert P (eds) Guidelines on techniques in coccidiosis research. European Commission, Directorate-General XII, Science, research and development environment research programme, pp 52–73Google Scholar
- Long PL, Millard BJ, Joyner LP, Norton CC (1976) A guide to laboratory techniques used in the study and diagnosis of avian coccidiosis. Folia Vet Lat 6:201–217Google Scholar
- Pakandl M, Gaca K, Licois D, Coudert P (1996b) Eimeria media Kessel 1929: comparative study of endogenous development between precocious and parental strains. Vet Res 27:465–472Google Scholar