Comparative Study On The Infection Rate Of Mycoplasma Pneumoniae In Different Sheep Breeds In Xinjiang

Objective: Mycoplasma ovipneumoniae(MO)is a highly contagious disease caused by mycoplasma infection,which is extremely harmful to the development of sheep industry in Xinjiang.Through serological investigation for disease,we can understand the infection of Mycoplasma ovipneumoniae of different sheep breeds in large-scale sheep farms of Xinjiang.To screen the candidate gene NLRP3 SNP,to explore the correlation between the polymorphism of NLRP3 SNP and the infection rate of sheep mycoplasma pneumonia.The correlation between polymorphism of this gene loci and infection rate of Mycoplasma ovipneumoniae was explored by screening candidate gene NLRP3 SNP loci.Methods: In this study,serological detection of Mycoplasma ovipneumoniae antigen and antibody was performed in the serum samples of 1628 non-immunized sheep from 4 sheep breeds in Bayingol Mongolian Autonomous Prefecture(Bazhou)of South Xinjiang and Ili Kazak Autonomous Prefecture(Ili)of North Xinjiang by using Mycoplasma ovipneumoniae enzyme-linked immunosorbent assay(ELISA)kit.On the basis of this experiment,NLRP3 gene was selected as the candidate gene,and the single nucleotide variants(SNV)in the coding sequence(CDS)of NLRP3 gene was detected by direct sequencing.The genetic polymorphism of Kazak sheep,Bayinbuluke sheep,Dorper sheep and Suffolk sheep was analyzed to identify the rule of genotype distribution,and the correlation of infection rate of Mycoplasma ovipneumoniae was analyzed for missense mutation loci.Result: After serological investigation,it was found that MP infection occurred in different sheep breeds from two areas of Xinjiang.In Ili area,the positive rate of MP antigen(Ag)and MP antibody(Ab)were 20.29% and 16.62%,respectively.Among them,there were 20.04% and 23.22% in Kazak sheep,respectively;the positive rate of MP-Ag and MP-Ab were 20.61% and 8.30% in Suffolk sheep,respectively.In Bazhou area,the positive rate of MP-Ag and MP-Ab was 14.42% and 14.65%,respectively.Among them,the positive rate of MP-Ag and MP-Ab were 17.91% and 18.65% in Bayinbuluke sheep,11.08% and 11.08% in Dorper sheep,and 14.70% and 13.23% in Suffolk sheep,respectively.Through the analysis of SNP loci in the coding sequence(CDS)of NLRP3 gene,14 SNP loci in the coding sequence were screened out,among which the missense mutation occurred in exon 3,rs161871942,and the amino acid changed from methionine to arginine(M645R).There were 3 genotypes in the third exon rs161871942(M645R)of NLRP3 gene in four sheep breeds: GG,GA and AA.There were significant differences in the distribution of genotypes in some sheep breeds(P < 0.05).There were 3 genotypes in the fifth exon rs403816614 of NLRP3 gene in Kazak sheep,Suffolk sheep and Dorper sheep: TT,TG and GG;there were GG and TG genotypes in Bayinbuluke sheep;there were significant differences in the genotype distribution between Kazak sheep and Suffolk sheep and Dorper sheep(P < 0.05);there were significant differences in the genotype distribution of Bayinbuluke sheep and Dorper sheep at this loci(P < 0.01).There were 3 genotypes of rs109222749 loci in exon 8 of NLRP3 gene in Kazak and Bayinbuluke sheep: CC,CT and TT,and CC and CT genotypes occurred in Suffolk and Dorper sheep populations;the genotypes distribution of four sheep breeds was significantly different(P < 0.05).There was a significant difference in the frequencies of MP-Ab positive and MP-Ab negative genotypes in Kazak sheep and Dorper sheep at the loci rs161871942(M645R)of exon 3 of NLRP3 gene(P < 0.05);there was no difference in the frequencies of MP-Ab positive and MP-Ab negative genotypes and alleles in Suffolk sheep and Bayinbuluke sheep(P > 0.05).Conclusion:The results of serology showed that the infection of Mycoplasma ovipneumoniae was common in different sheep breeds from large-scale sheep farms in Bazhou area of South Xinjiang and Ili area of North Xinjiang,and the positive rate in the detection of Mycoplasma ovipneumoniae antibody in different sheep breeds from different areas was higher than that of the imported breeds in the same area;The infection rate of antibody level of sheep Mycoplasma ovipneumoniae is different in different ages.The rs161871942(M645R)loci of NLRP3 gene may be correlated with MP infection rate of Kazak and Dorper sheep,but it may not be correlated with MP infection rate of Suffolk and Bayinbuluke sheep.This study provided a reference for the evaluation of the prevalence of Mycoplasma ovipneumoniae in Xinjiang and the breeding of disease resistance in sheep.