Molecular Epidemiological Investigation And Identification Of Mycoplasma Bovis In Large Scale Cattle Farms In Southern Xinjiang

Mycoplasma bovis is a cause of multiple diseases of cattle,such as bronchopneumonia,mastitis and arthritis.It has been widely spread in the world and caused great economic losses to cattle industry in various countries.In order to understand the prevalence of Mycoplasma bovis in some areas of Southern Xinjiang,a total of 350 nasal swabs and 3 lung samples of dead cattle were randomly collected from 10 large-scale cattle farms in Aksu,Hetian,Bazhou and Tumushuke from 2019 to 2020.The samples were detected by PCR using Mycoplasma bovis specific primers and Mycoplasma generic primers.The PCR positive samples were sequenced,and the sequences were analyzed by using biological analysis software mega and DNA star.Phylogenetic tree was constructed based on 16 S r RNA gene sequence;Modified Haflick medium was used to isolate and culture Mycoplasma,and colony morphology of the isolates was observed by light microscope,and then PCR method was used to further determine the species of the isolates.PCR results showed that 80 positive samples of Mycoplasma bovis and 238 positive samples of Mycoplasma were detected in 350 nasal swabs.The positive rates of Mycoplasma bovis in the four regions were 23.93%,26.04%,20% and 19.44% respectively,and the total positive rate of Mycoplasma bovis was 22.86%.The positive rates of Mycoplasma were 76.07%,58.33%,66.15%and 69.44% respectively,and the total positive rate of Mycoplasma was 68.00%.All the lung samples were positive for Mycoplasma bovis by PCR.The positive rate of Mycoplasma in calves was higher than that in adult cattle.Phylogenetic analysis showed that the 16 S r RNA gene sequences of Mycoplasma collected in this study could be classified into three types: Mycoplasma bovis,Mycoplasma bovirhinis and Mycoplasma bovoculi.Among them,Mycoplasma bovis was closely related to cq-w70 and pg45 strains,Mycoplasma bovirhinis was closely related to gs01 and pg43 strains,and Mycoplasma bovoculi was in the same branch with m165 / 69 strains.The results of Mycoplasma isolation showed that 15 strains of Mycoplasma were isolated from selected samples.According to the relative sequences published in Gen Bank,the results showed that the homology of 3 isolates in this study with Mycoplasma bovis was 99.7% ～ 100%,and that of 12 isolates with Mycoplasma bovirhinis was 98.8% ～ 100%.Therefore,they were identified as Mycoplasma bovis and Mycoplasma bovirhinis respectively at molecular level,and no Mycoplasma bovoculi was isolated.This study confirmed that there are three species of Mycoplasma epidemic in cattle farms in southern Xinjiang,the relevant departments should strengthen the introduction,transportation and quarantine,the farms should strengthen the feeding management,and regularly monitor the cattle,in order to prevent affecting the healthy development of local animal husbandry.