Epidemiologic survey and genotyping of Enterocytozoon bieneusi in sika deer (Cervus nippon) in four provinces of China.

Microsporidia are obligate intracellular parasites with a wide host range. To elucidate the relationship between Enterocytozoon bieneusi infection dynamics and evolution within China's sika deer population, 466 fresh fecal samples were collected from May to October 2024 across four provinces, Jilin, Liaoning, Heilongjiang, and Shandong. The ITS region of ribosomal RNA (rRNA) was amplified using nested PCR, enabling the identification and genotyping of E. bieneusi. The overall prevalence of E. bieneusi in sika deer was 44.4% (207/466). Province-specific prevalence was highest in Shandong (76.0%, 38/50) and Heilongjiang (75.3%, 67/89), followed by Jilin (38.7%, 65/168), and lowest in Liaoning (23.3%, 37/159). The prevalence in autumn (44.9%) was slightly higher than in summer (41.7%), and the prevalence in adult deer (48.7%) was found to be significantly higher than in young deer (31.6%). In this study, we identified a total of 11 E. bieneusi genotypes, including 9 known genotypes (BEB6, HND-II, LND-I, JLD-XIX, CHN-F1, HLJD-I, HLJD-III, Type IV, and COS-I) and 2 novel genotypes (named JL-D-4 and JL-D-5). Among them, BEB6 was the dominant genotype (38.7%, 80/207). This study enriches the genotype data of E. bieneusi, reveals the prevalence of E. bieneusi in some sika deer populations, and provides a reference for subsequent epidemiologic research as well as prevention and control efforts.