Jin Yue, Fei Jilan, Cai Jinzhong, Wang Xiaolan, Li Na, Guo Yaqiong, Feng Yaoyu, Xiao Lihua
State Key Laboratory of Bioreactor Engineering, School of Resource and Environmental, East China University of Science and Technology, Shanghai 200237, China.
Qinghai Academy of Veterinary Medicine and Animal Science, Xining 810016, China.
Vet Parasitol. 2017 Nov 30;247:70-76. doi: 10.1016/j.vetpar.2017.09.021. Epub 2017 Sep 27.
Giardia duodenalis is a common gastrointestinal protozoon in mammals. Although many studies have been reported on the distribution of G. duodenalis genotypes in sheep and cattle raised under intensive farming, few studies are available on the distribution of G. duodenalis in Tibetan sheep and yaks, which are raised free ranging in a continental plateau climate. In this study, 495 fecal specimens from Tibetan sheep and 605 from yaks were collected from eight counties in Qinghai, China and analyzed for G. duodenalis by PCR targeting the β-giardin (bg), glutamate dehydrogenase (gdh), and triosephosphate isomerase (tpi) genes. Based on PCR positivity at the bg locus, G. duodenalis occurrence rates were 13.1% (65/495) in Tibetan sheep and 10.4% (63/605) in yaks. DNA sequence analysis identified the presence of G. duodenalis Assemblages A (in 10 Tibetan sheep and 2 yaks) and E (in 51 Tibetan sheep and 60 yaks). In addition, mixed infections of the two were identified in four Tibetan sheep and one yak. Among the sequences obtained in this study, 1, 10, and 2 new subtypes of Assemblage E were detected at the bg, gdh and tpi loci, respectively. Based on sequences from the three loci, 28 multilocus genotypes (MLGs) were obtained, including 27 MLGs in Assemblage E and one MLG in Assemblage A. Each MLG was found in no more than seven animals, with most MLGs forming host-specific clusters in phylogenetic analysis except for one cluster including MLGs from both Tibetan sheep and yaks. Only two MLGs were found in both sheep and yaks. The above results demonstrate a high subtype diversity of G. duodenalis Assemblage E in Tibetan sheep and yaks raised in a traditional animal husbandry system and suggest that only limited cross-species transmission of G. duodenalis occurs between yaks and sheep sharing pastures.
十二指肠贾第虫是哺乳动物中一种常见的胃肠道原生动物。尽管已有许多关于集约化养殖的绵羊和牛中十二指肠贾第虫基因型分布的研究报道，但对于在大陆高原气候下自由放养的藏绵羊和牦牛中十二指肠贾第虫的分布情况，相关研究较少。在本研究中，从中国青海的八个县采集了495份藏绵羊粪便样本和605份牦牛粪便样本，通过针对β-贾第虫蛋白（bg）、谷氨酸脱氢酶（gdh）和磷酸丙糖异构酶（tpi）基因的PCR方法分析其中的十二指肠贾第虫。基于bg位点的PCR阳性结果，藏绵羊中十二指肠贾第虫的感染率为13.1%（65/495），牦牛中为10.4%（63/605）。DNA序列分析确定存在十二指肠贾第虫A群（10只藏绵羊和2头牦牛）和E群（51只藏绵羊和60头牦牛）。此外，在4只藏绵羊和1头牦牛中鉴定出了两者的混合感染。在本研究获得的序列中，分别在bg、gdh和tpi位点检测到E群的1个、10个和2个新亚型。基于三个位点的序列，获得了28个多位点基因型（MLGs），包括E群中的27个MLGs和A群中的1个MLG。每个MLG在不超过7只动物中被发现，除了一个包括来自藏绵羊和牦牛的MLGs的聚类外，大多数MLGs在系统发育分析中形成宿主特异性聚类。在绵羊和牦牛中仅发现了两个MLGs。上述结果表明，在传统畜牧系统中饲养的藏绵羊和牦牛中，十二指肠贾第虫E群具有高度的亚型多样性，并且表明在共享牧场的牦牛和绵羊之间，十二指肠贾第虫的跨物种传播有限。
