Blastocystis is the most frequent parasite that has been reported in humans and a variety of animals with controversial pathogenicity[18, 19], previous studies have found that infection with Blastocystis is linked to nutritional and gastrointestinal disorders in both developing and developed countries[20]. However, recent microbiome studies have reported that the presence of Blastocystis may be an indicator of good intestinal health[21]. Zoonotic STs is supposed to be commonly transmitted between animals and humans, and some certain STs of animal origin are significant potential reservoirs for human infections[22–24].
Epidemiological studies have been conducted in domestic animals including pig, cattle, dairy cattle, sheep and goat but only few reported on captive wildlife has been documented in China[2]. The prevalence of Blastocystis in wild animals examined in this study was 10.0% (30/300), which was lower than that of captive wild animals from zoo animals in Western Australian (42%, 32/76)[3], in Qinling Mountains, China (40.2%, 200/497)[25], in zoo animals in Japan (39.0%, 46/118)[26], in wild animals in Brazil (34.4%, 115/334)[27], in zoo animals in United Kingdoms (34.2%, 79/231), and in various captive animals in French (32.2%, 99/307)[28] in captive wildlife in four zoos outhwestern China(15.7%, 66/420)[14] and in captive mammalian wildlife in Bangladesh National Zoo (15.5%,31/200)[24]. While in this study the Blastocystis prevalence in wild animals was higher than that in zoo animals in three cities in China (6.0%, 27/450)[29]. At this time, it is unclear how those factors contribute to affect the prevalence, between countries or within the same country, such as the conditions in which the animals were housed, animal species, size of examined samples, or management methods.
In the present study, the prevalence of Blastocystis in nonhuman primates (NHPs) was 20.0%, which is higher than that in rodentia (14.3%), artiodactyla (13.1%), carnivora (2.3%), and galliformes (0.0%) and five Blastocystis STs, including ST1, ST3, ST5, ST13 and ST14, were identified in 30 Blastocystis-positive samples from 4 orders wildlife (Table 4). To date, These STs have been documented from primates in Europe such as monkeys and macaque[28, 30–32] and Brazil[27]. ST4, ST5, and ST8 have also been found in monkeys elsewhere[27, 30, 31, 33]. In the current study, sequences obtained from primates belonged to ST5. These isolates were infecting the golden monkey. The presence of ST5 has also been found sporadically in humans in close contact with animals, suggesting zoonotic transmission[34, 35].
Previous studies have confirmed that other STs, such as ST1-3, ST5, ST7, ST8, ST10, and ST17 has been identified in rodents[36, 37] and in this study, ST1 was identified in rodents (porcupine), corroborating previous data on rodents. Wistar rats infected with ST1 could cause moderate and severe degrees of pathological changes, This subtype indicated the potential pathogenicity, Hussein et al. Reported[38].
Five subtypes (ST1, ST3, ST5, ST13 and ST14) were identified in artiodactyla ( long-tailed goral, sika deer, sambar, crested deer, chinese antelope and blue sheep) In this study. Previous studies reported many animals in the order of artiodactyla harboring the Blastocystis, such as cattle, pigs, sheep, deer, and goats[2, 39]. To date, the majority of STs such as ST1, ST3, ST5, ST13 and ST14 have been identified in artiodactyla[36, 40]. In artiodactyla ST1 was found in sika deer and long-tailed goral, ST3 was identified in sika deer, ST5 were found in long-tailed goral, ST13 was found in sambar, long-tailed goral, crested deer, blue sheep and ST14 was identified in sambar, crested deer, chinese antelope and blue sheep in present study. Many previous surveys have indicated that, in human the ST1 and ST3 have been reported as the two most common subtypes in different countries[41, 42]. Which proposed a hypothesis of the potential transmission of Blastocystis infection between human and artiodactyla. Therefore, the role of artiodactyla to transmit these subtypes should be further evaluated in the future study. As reported, ST5 was the most predominant subtype in pigs[43], and it also identified in a various animals, such as cattle, sheep, NHPs, and birds[39]. The surprise is that a rare ST (ST13) was also determined in Java mouse-deer in France[28], in a mouse deer in United Kingdoms[36]. Meanwhile, sheep in China[44], muntjac deer in the United Kingdoms[37] were found infected with ST14.
In the current study, sequences obtained from carnivora belonged to ST14. These isolates have infected the sand badger and leopard cat. ST14 is often reported in artiodactyls but is almost absent in the carnivore order[37].