Epidemiological Investigation And Preliminary Formulation Of Immunization Program Of Sheep Mycoplasma Pneumonia In A Large-scale Sheep Farm

Objective: In order to understand the infection of sheep mycoplasma pneumonia in a large-scale sheep farm in Xinjiang,this study plans to conduct an epidemiological investigation of sheep mycoplasma pneumonia in this large-scale sheep farm,isolate the pathogen and analyze the sensitivity to drugs and disinfectants.On this basis,explore the prevention and control scheme based on vaccine immunization,in order to provide reference for the prevention and control of sheep mycoplasma pneumonia in this large-scale sheep farm.Methods:(1)Field epidemiological investigation.The scale of sheep farm and the production status of sheep were investigated,and the incidence of sheep respiratory diseases and sheep mycoplasma pneumonia were statistically analyzed.(2)Seroepidemiological investigation.The positive indirect hemagglutination test(IHA)was used to detect and analyze the serum antibodies of sheep Mycoplasma pneumoniae(Mo)and goat Mycoplasma pneumoniae subspecies(Mccp)in different stages and breeds of sheep in the sheep farm.(3)Molecular epidemiological survey.The collected disease materials were detected by PCR with specific primers of Mycoplasma ovine pneumoniae,Mycoplasma mycoides subspecies,Mycoplasma goat subspecies,Mycoplasma goat subspecies of pneumonia and Mycoplasma arginine.Some samples were selected for gene sequencing and their molecular characteristics were analyzed.(4)Separation and main characteristic analysis of mo.The positive samples were isolated and cultured,the 16 S r RNA and P30 gene of the isolates were amplified and sequenced,the sequencing results were analyzed by bioinformatics software,and the phylogenetic tree was constructed;The minimal inhibitory concentration(MIC)and minimal bactericidal concentration(MBC)of 13 common antibiotics were determined by microdilution method;Five common environmental disinfectants such as phenols,quaternary ammonium salts and chlorine were selected for sensitivity analysis by spectrophotometry.(5)Preliminary formulation of immunization programme.On the basis of epidemiological investigation,commercial vaccines were selected,and the growth and decline of antibodies after immunization were measured and analyzed by positive and indirect hemagglutination method.Results:(1)The management level of the sheep farm is relatively backward.From December 2020,the number of respiratory diseases and lamb deaths in the sheep farm showed an upward trend.The incidence of sheep is mostly concentrated from December to April of the next year.The lambs aged 31-45 days and46-60 days in this farm are the high incidence days of respiratory diseases,and most of them are Hu sheep.(2)Serological investigation results: the average positive rate of Mo was 50.42%;The highest positive rate of Hu sheep was 79.17%;The highest positive rate was in non weaned lambs,with a positive rate of75.00%.In addition,anti Mo and anti Mccp antibodies were detected in some sera at the same time.(3)Molecular epidemiological investigation: the overall positive rate of Mycoplasma was 50.49%,the positive rate of Mo was 43.69%,and the positive rate of Ma was 6.80%;The highest infection rate of Hu sheep Mo was 54.28%.The sample Mo.10 had the highest affinity with Mycoplasma ovipneumoniae strain FJ-SM.(Mycoplasma ovipneumoniae strain FJ-SM.KU870650.1)and the sample Mo.9 had the closest affinity with Mo GH3-3 isolated from Lanzhou Institute of veterinary medicine,Chinese Academy of Agricultural Sciences.Other sequencing strains formed a separate branch;Mycoplasma arginine sample ma6 has the closest affinity with C1 strain(HQ661823.1)and G230 strain(NR 041743.1).(4)Isolation and main characteristic analysis of Mo: two strains of Mo were successfully isolated and named HR-1 and HR-2 strains;The homology showed that the homology between the isolate and Mo y98 was as high as98%,and there were partial base deletion or variation in the outer membrane protein P30 gene;HR-1 is sensitive to ciprofloxacin hydrochloride,azithromycin and other drugs,HR-2 is sensitive to ciprofloxacin hydrochloride,azithromycin,doxycycline and other drugs;The disinfection effect shows that the effect of sodium hydroxide is better than that of other disinfectants.(5)Exploration of immunization scheme: choose inactivated goat Mycoplasma vaccine(Mo GH3-3 + M87-1 strain),the first immunization protection period can reach 4 months,and the second immunization protection period can reach 6 months.Conclusion: The epidemic of sheep mycoplasma pneumonia in this large-scale sheep farm is relatively serious.Sheep Mycoplasma pneumoniae is the main epidemic strain.If goat Mycoplasma inactivated vaccine(Mo GH3-3 + M87-1 strain)is selected,the first immune protection period can reach 4 months and the second immune protection period can reach 6 months.