Molecular Prevalence and Genetic Characterization of Toxoplasma gondii in Wild Birds in Hunan Province,China

Introduction

T oxoplasma gondii is an important zoonotic parasite that can infect many animals and humans. It is estimated that up to a third of the world's population and ∼8% of Chinese has been infected with T. gondii (Zhou et al. 2011). Humans can become infected by eating food containing T. gondii oocysts (Dubey 2010). Wild and domestic felids are the only known definitive hosts for T. gondii, while a wide variety of warm-blooded animals, including wild birds, are considered as intermediate hosts (Dubey 2002). T. gondii is an important pathogen that could cause miscarriage and even death in various animals and humans (Dubey 2010).

An increasing number of teams have been focusing on the prevalence and genotypes of T. gondii in many animals and humans (Shwab et al. 2014, Cong et al. 2015, Chaichan et al. 2017). Different genotypes of T. gondii have been found in different hosts and geographical origins. Most of the T. gondii in North America and Europe can be divided into three clonal lineages (Types I, II, III) by PCR-restriction fragment length polymorphism technology (PCR-RFLP) (Shwab et al. 2014). In addition, more loci of microsatellite parting enzyme electrophoresis technology have been applied to detect genetic variability among T. gondii isolate from Africa and South America (Darde et al. 1992, Howe and Sibley 1995, Ajzenberg et al. 2002, Shwab et al. 2014, Galal et al. 2018, Pomares et al. 2018). In China, the prevalence and genotypes of T. gondii have been reported in many hosts, such as humans, cats, donkeys, pet birds, and wild birds (Zhou et al. 2009, Chen et al. 2011, Huang et al. 2012, Cong et al. 2014, 2018). ToxoDB #9, so-called Chinese I isolate, was the prevailing genotype in animals and humans in China (Jiang et al. 2014, Cong et al. 2015, 2016). Hunan province has one of the richest biodiversity heritage status (Li et al. 2009); however, limited information is available about the prevalence and genotypes of T. gondii in this province, China (Zhou et al. 2009).

T. gondii infection in various birds has been reported from different countries (Dubey 2002, Cenci-Goga et al. 2011). As the intermediate host of T. gondii, wild birds can transmit T. gondii by carrying—tachyzoite/bradyzoite, which play an important role in the spread of T. gondii. Importantly, wild birds were often caught illegally, as tasty game, posing a potential risk for T. gondii infection in human. Therefore, the objective of this study was to determine the prevalence and genotypes of T. gondii in wild birds in Hunan province of China. Our results should provide a foundation for the prevention and control T. gondii infection in Hunan province and elsewhere in China.

Materials and Methods

Results and Discussion

In the present study, 13 (5.51%) of 239 samples were positive for the T. gondii (Table 1), which was higher than that 2.25% (4/178) in wild birds from around China (Huang et al. 2012), 3.51% (11/313) in house sparrows from Lanzhou, China (Cong et al. 2013), and 2.14% (3/140) in pet birds from Fujian province, China (Chen et al. 2015), but lower than that 7.2% (18/249) in wild waterfowls from Jilin province, Northeastern China (Zhang et al. 2015). Besides, the prevalence of T. gondii in wild birds was significantly lower than that in mammals, such as 10% (10/100) in red foxes (Lukasova et al. 2018) and 15.45% (57/367) in badgers (Chen et al. 2017). The differences in prevalence may be related to the number of wild and domestic felids present in those regions.

The 13 positive samples include 1 from olive-backed pipit (1/44, 2.27%), 1 from yellow chest bunting (1/26, 3.85%), and 11 from tree sparrows (11/131, 8.40%) (Table 1). Due to the low DNA concentration of T. gondii, only 3 samples from tree sparrows were completely genotyped at all gene loci (Fig. 1), and these were identified as Type I (ToxoDB #10) that was widely prevalent in China (Table 2) (Qin et al. 2014, Cong et al. 2015, Miao et al. 2015). Remarkably, the genotypes ToxoDB #9 and ToxoDB #10 were frequently detected in cancer patients (Cong et al. 2015) and animals, including raccoon dogs, poultry meat, and donkey meat (Zhou et al. 2017, Zou et al. 2017, Cong et al. 2018), indicating that cross infection had occurred between humans and animals in China. Therefore, further investigation should be implemented to find that whether cross infection could also have occurred in Hunan province, China.

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FIG. 1.

Analysis of genotyping of Toxoplasma gondii by PCR-RFLP based on 12 loci in wild birds in Hunan province, China. Lanes 1–11: GT1, PTG, CTG, MAS, TgCgCa1, TgCatBr5, TgCatBr64, TgRsCr1, 151, 153, and 158, respectively. PCR-RFLP, PCR-restriction fragment length polymorphism technology.

Sparrow is a very common wild bird in most countries, and the prevalence of T. gondii range from 0% to 25.56% in house or tree sparrows around the world (Literak et al. 1997, Gondim et al. 2010, Huang et al. 2012, Cong et al. 2013, Khademvatan et al. 2013, Abdoli et al. 2016). To date, limited information is available about the T. gondii genotype in sparrows (Huang et al. 2012, Cong et al. 2013, Khademvatan et al. 2013). Previous studies have indicated that ToxoDB #10 (Type I) has been found in tree sparrows (Huang et al. 2012), and Type II variants, ToxoDB #3 in house sparrows (Huang et al. 2012, Cong et al. 2013, Khademvatan et al. 2013), revealing multiple genotypes of T. gondii can be carried by sparrows. Although ToxoDB #9 is the most commonly prevalent in China, only ToxoDB #10 was identified in this study. This is most likely related to geographical distribution of T. gondii genotypes. In addition, birds are part of the alimentary chain of many animal species, and wild felids also live in this region, keeping the sylvatic cycle of T. gondii in Hunan province. However, only one genotype was detected in this province that is home to 463 species of wild birds. To understand the genotype distribution of T. gondii in animals in this province it thus emphasizes the need for more investigations on T. gondii in animals in Hunan province, China.

Although the seroprevalence of T. gondii infection was 29% (36/124) in field mice (Zhang et al. 2004), 31.3% (373/1191) in sows (Xu et al. 2014) and 12% (124/1028) in goats (Li et al. 2016) in Hunan province, limited information is available on T. gondii genotypes in Hunan province, China (Zhou et al. 2009). In the present study, one genotype (ToxoDB #10) was identified in wild birds, consistent with that of previous study (Huang et al. 2012). The previous and present study indicated that T. gondii infection is prevalent in animals (goat, sows, rat, and wild birds) in Hunan province, China (Zhang et al. 2004, Xu et al. 2014, Li et al. 2016), but this situation has received little attention in the past. Importantly, humans can acquire T. gondii infection from many animals, including wild birds (Dubey 2002), therefore, it is imperative to apply integrated control strategies and measures to prevent and control T. gondii infection in domestic animals, and public should be educated and enlightened to cultivate awareness to avoid consuming wildlife.

In conclusion, in this study, a total of 5.51% (13/239) brain tissues of Passeriformes wild birds were detected to be positive for the T. gondii infection in Hunan province, China. Only one genotype (ToxoDB #10) was identified in wild birds. This is the first report of the molecular prevalence and genetic characterization of T. gondii in wild birds in Hunan province, China, which would provide a foundation for the prevention and control of T. gondii infection in Hunan province and elsewhere in China.