The infection rate of E. bieneusi in rodent species varies from 2.5% to 100% worldwide [13, 14]. To the best of our knowledge, this is the first report of E. bieneusi infections in coypus in China. In the present study, the infection rate of E. bieneusi was 41.2% in coypus, which is higher than the infection rate of E. bieneusi reported in brown rats (7.9%) [8], bamboo rats (5.1%) [15], experimental brown rats (4.8%) [16], commensal rodents (mouse and brown rat) (4.0%) [14], pet chinchillas (3.6%) [17] and red squirrels (19.4%) [18] in China. In addition, lower infection rates were also reported in wild house mice (10.7%) from a hybrid zone across the Czech Republic-Germany border [19], and beavers (15.3%) and muskrats (8.4%) from USA [20]. However, higher infection rates of E. bieneusi were reported in chipmunks (71.4%) and woodchucks (100%) from USA [13]. Similar infection rates of E. bieneusi have been reported in small rodents (mouse, bank vole, yellow-necked mouse and striped field mouse) (38.9%) from southwestern Poland [21], and a laboratory prairie dog colony (37.9%) from USA [22]. The infection rates of E. bieneusi in rodents could be influenced by many factors, such as animal immune status, age distribution, sample size, detection method, feeding environment, management system and population density [16]. Because the high infection rate detected in coypus in our study, we can draw a preliminary inference that coypus are more susceptible to E. bieneusi than many other rodent species, which should be confirmed by more investigations in the future.
A variation of positive rate of E. bieneusi in coypus was observed in the present study with the highest being detected in Anyang (72.3%, 73/101) and the lowest in Laibin (9.1%, 2/22). Geographical location-based variation in the prevalence of E. bieneusi in rodents has been reported. Such as in brown rats in different provinces in China, which was ranged from 2.9% to 14.7% [8, 14, 16, 23, 24]. This phenomenon has also been reported in other animals, for example, in alpacas (Vicugna pacos) in China (0 – 42.9%) [25] and in Asiatic black bear (Ursus thibetanus) in China (0 – 50%) [26]. The difference may be related to geographical environments and feeding density.
In the present study, the dominant genotype of E. bieneusi was CHN4, which was detected in six cities except Yongzhou, indicating that genotype CHN4 is commonly found in coypus in China. This genotype has been identified in three human and two cattle samples [27] and four pre-weaned calf samples [28] from China, and it was firstly found in coypus here. These finding indicated that genotype CHN4 has a wide range of animal reservoirs and potential for zoonotic transmission. Genotype D was identified in squirrels from China [29] and USA [13], chipmunks [30], bamboo rats [15] and brown rats [8, 23] from China, house mice from Czech Republic-Germany border [19] and striped field mice from Poland [21], and genotype WL4 was observed in squirrels, chipmunks and muskrats from USA [13, 20] (Table 3). EbpA, EbpC, PigEBITS7, S7, Peru16 and CHG14 have also been reported as the most common genotypes in experimental brown rat, beaver, giant rat, guinea pig, guinea pig and brown rat, respectively [10, 14, 16, 20, 23, 31]. Additionally, in a more recent study of E. bieneusi in Himalayan marmots (Marmota himalayana) and Alashan ground squirrels (Spermophilus alashanicus) revealed that genotype ZY37 was the most common one [9].The rare genotype CHN4 was the dominant genotype, indicating that the transmission dynamic of E. bieneusi in coypus is different from other rodents. This may be explained by the unique life habits of coypus as aquatic rodents compared to other rodents involved in previous studies.
Genotype EbpA and EbpC have been detected in several rodent species (squirrel, house mouse, experimental brown rat, muskrat, bamboo rat and beaver) worldwide [15, 16, 19, 20, 29] (Table 3). They are two of the most common genotypes detected in both immunocompetent and immunocompromised people worldwide [1]. Meanwhile, genotype EbpA and EbpC have a vast host range, such as non-human primates (NHPs), livestock (cattle, buffalo, sheep and goat), pets (dog and horse), wild animals (deer, fox, raccoon, bear, panda and otter) and birds (pigeon, crane and parrot) [1]. These two genotypes also have been observed in lake water [32], river water [33] and wastewater treatment plants [34, 35]. According to these data, the interspecies transmission of genotype EbpA and EbpC pose a zoonotic risk to human or other animals, and coypus may serve as a reservoir of EbpA and EbpC in the E. bieneusi transmission.
In the phylogenetic analysis, an NJ tree was constructed and the novel genotype CNCP1 clustered with CHN4, EbpC and EbpA in group 1. The majority of the zoonotic genotypes belongs to the group 1, and genotypes CHN4, EbpC and EbpA have been reported in humans [27, 36, 37], indicating that genotype CNCP1 maybe has zoonotic potential and the E. bieneusi isolates in coypus detected in this study can be transmissible from coypus to humans, especially the animal handlers, or vice versa.