Occurrence, Histopathological Findings, and Molecular Identification of Pathogenic Eimeria Infections in Rabbits (Mammalia: Lagomorpha) in Japan

Purpose Eimeria spp. are commonly found among rabbits (Mammalia: Lagomorpha) worldwide. Among the 11 Eimeria species, several are highly virulent, including E. intestinalis and E. flavescens , which cause intestinal coccidiosis, and E. stiedae , which causes hepatic coccidiosis. Unlike other countries, the occurrence of Eimeria infections in rabbits in Japan remains unknown, except for one reported case of natural infection. Methods We surveyed Eimeria infections in clinically affected rabbits over the past approximately 10 years at Livestock Hygiene Centers in 42 prefectures. A total of 16 tissue samples (14 liver, 1 ileum, and 1 cecum) were collected from 15 rabbits in 6 prefectures. Results Characteristic histopathologic findings were observed, especially around the bile ducts, depending on the developmental stages of the parasites. Eimeria stiedae and E. flavescens were successfully identified by PCR and sequencing analyses in 5 liver samples and 1 cecum sample, respectively. Conclusion Our results could enhance understanding of infection with Eimeria spp. in rabbits in Japan and contribute to pathological or molecular diagnoses.