| Giardia duodenalis is a common gastrointestinal protozoon in mammals.G.duodenalis can cause infected animals indigestion,diarrhea,abdominal pain and slow growth,resulting in harm to human health and loss of livestock.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.Therefore,we investigated the distribution of G.duodenalis in yaks and Tibetan sheep in Qinghai Province by multilocus genotyping(MLG)technology,and compared it with the results obtained from the intensive farming dairy cattle(post-weaned)in Jiangsu Province to analyze the prevalence of G.duodenalis in different farming methods.In order to analyze the distribution of G.duodenalis in yak,Tibetan sheep and dairy cattle,we collected a total number of 1100 fecal specimens from eight counties in Qinghai Province,including 495 samples of Tibetan sheep fecal,605 samples of yak fecal,as well as 512 samples of dairy cattle from Xinhua,Jiangsu Province.Those specimens were analysed for G.duodenalis by PCR targeting the ΞΎ-giardin(bg),glutamate dehydrogenase(gdh),and triosephosphate isomerase(tpi)genes.Multilocus genotyping(MLG)technology was used to divide genotypes and subtypes.According to the positive results of three loci,the constructions concerning naming methods and phylogenetic tree can be applied to genetic relationship.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,10,18 and 7 subtypes of Assemblage E were detected at the bg,gdh and tpi loci,including 1,10,and 2 new subtypes,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.We have detected 40 positive samples from 512 weaning cows in Xinghua,Jiangsu Province and the positive rate was 7.8%.Among those specimens,the positive rate of G.duodenalis reached to 96.7%in one-week weaning dairy cattle.The specimens were mainly detected as Assemblage E and one zoonotic subtype A1 were respectively detected at bg and gdh loci.Among the sequences obtained in this study,6,5,and 7 subtypes of Assemblage E were detected at the bg,gdh and tpi loci,respectively,and a new subtype were found in each locus.The dominant subtypes of each locus in dairy cattle shared among yaks and Tibetan sheep,suggesting these subtypes had long history and wide distribution,with the possibility of some cross-species transmission.Results of a phylogenetic analysis of the sequences obtained have revealed the presence of host-specific clusters of MLGs,with one Cluster only including the MLGs from dairy cattle.Furthermore,nucleotide differences were also found by comparing the MLG sequences obtained in Jiangsu Province with the MLGs obtained from Qinghai Province,showing the geological differentiation existed.The above results helped us to know the distribution of G.duodenalis in different species and different regions,and provided a theoretical basis for the prevention of transmission between animals and humans. |
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