Occurrence and Molecular Characteristics of Microsporidia in Captive Red Pandas (Ailurus fulgens) in China

SIMPLE SUMMARY: Microsporidia are obligatory intracellular fungi that cause infection in a broad variety of eukaryotes. However, there are few epidemiological studies on microsporidia in red pandas in China. Therefore, we conducted an epidemiological survey of microsporidia in red pandas from six zoos in Sichuan Province, China. In 198 fecal samples, Enterocytozoon bieneusi was detected in 24 samples (12.1%), while Encephalitozoon spp. was detected in 8 fecal samples (4.0%). Further analysis revealed the presence of genotypes of E. bieneusi with zoonotic concerns. Interestingly, we also observed that the infection rate of microsporidia was higher in semi-free red pandas with more frequent contact with other animals or humans. This is the first report on the occurrence and genotypes of E. bieneusi and Encephalitozoon spp. in red pandas in Sichuan Province, China, contributing to our understanding of the worldwide distribution and genetic diversity of this pathogen. ABSTRACT: Enterocytozoon bieneusi and Encephalitozoon spp. are microsporidian pathogens with zoonotic potential that pose significant public health concerns. To ascertain the occurrence and genotypes of E. bieneusi and Encephalitozoon spp., we used nested PCR to amplify the internal transcribed spacer (ITS) gene and DNA sequencing to analyze 198 fecal samples from red pandas from 6 zoos in China. The total rate of microsporidial infection was 15.7% (31/198), with 12.1% (24/198), 1.0% (2/198), 2.0% (4/198) and 1.0% (2/198) for infection rate of E. bieneusi, Encephalitozoon cuniculi, Encephalitozoon intestinalis and Encephalitozoon hellem, respectively. One red panda was detected positive for a mixed infection (E. bieneusi and E. intestinalis). Red pandas living in semi-free conditions are more likely to be infected with microsporidia (χ(2) = 6.212, df = 1, p < 0.05). Three known (SC02, D, and PL2) and one novel (SCR1) genotypes of E. bieneusi were found. Three genotypes of E. bieneusi (SC02, D, SCR1) were grouped into group 1 with public health importance, while genotype PL2 formed a separate clade associated with group 2. These findings suggest that red pandas may serve as a host reservoir for zoonotic microsporidia, potentially allowing transmission from red pandas to humans and other animals.