1. INTRODUCTION
Enterocytozoon bieneusi is a prevalent pathogen in humans and an important zoonotic agent in animals worldwide (Fayer and Santin-Duran, 2014). The most common clinical symptom of E. bieneusi infections is diarrhea for patients with Acquired Immunodeficiency Syndrome (AIDS) or other immunocompromising conditions while asymptomatic infections are common for healthy persons (Matos et al., 2012). Mostly, human acquire infections by ingesting the infectious spores of E. bieneusiwhich potential sources include: water, soil, environmental surfaces, fecal contamination, and improper manure or irrigation water practices in growing fruits and vegetables (Zhao et al., 2014; Li et al., 2012; Li et al., 2019; Santin and Fayer 2011). Thus, understanding the source and mechanism of transmission of E. bieneusi could prevent its spread in humans.
Previous studies detected E. bieneusi using PCR-based assays with appropriate gene markers (Santin and Fayer 2009). More than 500 genotypes, of which 142 infected humans and 49 infected both humans and animals, were identified through the internal transcribed spacer (ITS) sequence analysis of rDNA of the E. bieneusi (Zhou et al., 2020; Li et al., 2019; Zhao et al., 2020). These genotypes can be grouped into 11 genetically isolated clusters by phylogenetic analysis (Li et al., 2019). Group 1 is the largest group containing more than 300 genotypes, including 87.6% (132/142) human-pathogenic genotypes (Gong et al., 2019; Li et al., 2019). Meanwhile, 85.7% (42/49) zoonotic genotypes also belong to this group (Zhou et al., 2020; Li et al., 2019). In Group 2, up to 100 genotypes are considered to be adapted to ruminants; however, contrary to previous reports, a broader host range was indicated for some genotypes, such as genotypes I, J, BEB6, BEB4 and CHN3 are also commonly found in humans, enhancing their importance for public health (Li et al., 2019). Genotypes in Groups 3 to 11 have been mainly reported in specific hosts or wastewater (Guo et al., 2014). Group 1 or 2 are frequently reported in pets, non-human primates, wildlife, and livestock (pigs, cattle, sheep, etc.) (Li et al., 2019; Zhao et al., 2020). However, the mechanism of transmission of infection from a specific animal to humans is unclear.
Rodents have a high rate of multiplication as well as survival rate, which have resulted in their overpopulation. They are also the reservoirs or carriers of several types of zoonotic pathogens, includingE. bieneusi . Until now, sixty genotypes of E. bieneusi , including eighteen zoonotic genotypes (C, CZ3, D, BEB6, EbpC, Nig7, Peru6, Type IV, EbpA, PigITS7, H, S7, Peru8, S6, Peru16, J, Peru11, and PigITS5) have been identified in rodents, confirming their role in disease transmission (Li et al., 2020; Gui et al., 2019; Deng et al., 2016, 2018; Qi et al., 2015; Wang et al., 2019; Yu et al., 2019; Zhao et al., 2018; Perec-Matysiak et al., 2015; Danišová et al., 2015; Guo et al., 2014; Roelling et al., 2015; Sak et al., 2011; Cama et al., 2007)(Table 1) .
Previous studies have reported E. bieneusi infections in eight rodent species, including, brown rats (Rattus norvegicus ), bamboo rats (Rhizomys sinensis ), house mice (Mus musculus ), Bower’s white-toothed rats (Berylmys bowersi ), Edward’s long-tailed rats (Leopoldamys edwardsi ), Chipmunks (Eutamias asiaticus ), Chinchillas (Chinchilla lanigera ), and red-bellied squirrels (Callosciueus erythraeus ) in China. These studies involved five provinces with infection rates ranging from 3.6% to 35.1% (Gui et al., 2019; Deng et al., 2016, 2018; Qi et al., 2015; Wang et al., 2019; Yu et al., 2019; Zhao et al., 2018). Hainan Province of China where is rich in rodents and they closely contact with humans and other animals. Meanwhile, there is high prevalence ofE. bieneusi in farmed, household, and wild animals (Zhao et al., 2020; Zhou et al., 2019; Chen et al., 2019; Zhou et al., 2020), and was identified in humans with diarrhea (unpublished data) in Hainan, China. Thus, it is necessary to understand E. bieneusi epidemiology in rodents to prevent pathogen infection in humans as well as in other animals. This study explored the prevalence of E. bieneusi in rodents in several areas of Hainan Province of China, to evaluate the zoonotic potential of the isolates at the genotype level.