Epidemiological Investigation And Pathogen Biological Characteristics Of Streptococcus Sheep In Shigatse City

The stock of sheep in Shigatse accounts for more than 1/3 of the total,so the sheep industry plays a key role in the production and life of farmers and herdsmen in Shigatse.Streptococcus sheep is one of the important factors that endanger the health and green development of Shigatse sheep breeding industry,and it also seriously affects the economic income of local farmers and herdsmen.In order to better prevent and control the disease in the future,and to provide a scientific drug use plan,this study analyzed the biological characteristics of the disease from the epidemiological investigation of Streptococcus sheep,the isolation and identification of pathogens and the whole genome of highly pathogenic strains,so as to provide a scientific theoretical basis for the prevention and control of the disease.The main research contents are as follows:1 Seroepidemiological investigation of Streptococcosis in Sheep in Shigatse CityIn order to understand the epidemic situation of Streptococcus sheeps in some main sheep breeding counties（districts）in Shigatse,Tibet,1458sheep serum samples were collected from 5 counties（districts）in Shigatse from 2020 to 2021.Streptococcus antigens were detected by enzyme linked immunosorbent assay（ELISA）,and R software was used to analyze the sheep of different age,sex,breed,altitude,sampling year and different feeding mode.The results showed that the individual positive rate of Streptococcus sheeps in Shigatse was 6.93%（101 hand 1458）,and the population positive rate was 82%（41）.The results of statistical analysis showed that the individual positive rate of Streptococcus in 2020 was significantly different from that in 2021（OR=2.16,95%CI:1.39%～3.39%）,and that of sheep in low altitude（<4000m）was significantly different from that in high altitude（>4000m）（OR=0.62,95%CI:0.41,0.93）.The individual positive rate of Streptococcus sheep in farms was significantly different from that of sheep streptococci in herdsmen（OR=2.64,95%CI=1.71%～4.10%）.The results showed that sheep streptococcosis was still prevalent in Xigaze area,and there was no difference in age,sex,breed and altitude.It is suggested that local farmers should strengthen the feeding management and vaccine immunity of sheep so as to improve the immunity of local sheep.2 Isolation,Identification and Biological characteristics of Streptococcus from Sheep in Shigatse CityIn order to explore the current situation of streptococci infection in sheep in Shigatse area and the related biological characteristics of streptococci,the isolated strains were tested for drug sensitivity and grouping by isolation and culture,PCR identification and 16Sr RNA sequence amplification and sequencing.The results showed that 16 strains of Streptococcus aureus were isolated from 42 nose swabs,and the isolation rate was 38.10%.Among them,there were 9 strains of Streptococcus luteinus,5 strains of Streptococcus equi,1 strain of Streptococcus multianimal,1 strain of Streptococcus micrococcus,and 56.25%of Streptococcus luteum.In addition,through the hemolysis test,it was found that 1 strain showedβhemolysis and the others showedαhemolysis.The serum group grouping test showed that 14 strains of 16 strains of streptococcus were group C streptococci,the other 2 strains were group D streptococci,and group C was the dominant group prevalent in this area.The lethal rate ofβ-hemolytic streptococcus to mice was 100%,in which the LD₅₀of the strain was 4.86×10⁶CFU/ml.α-hemolytic streptococcus could cause mild diarrhea in mice.The results of drug sensitivity test of isolated strains showed that the sensitive rate of 16 streptococci to 10 antibiotics such as doxycycline,chloramphenicol,clindamycin,ofloxacin,vancomycin and penicillin was 50%to 100%.The resistance rate to polymyxin B,kanamycin,cefuroxime,gentamicin and amikacin was more than 50%.This study studied some biological characteristics of Streptococcus from sheep in Shigatse area,which laid a theoretical foundation for better prevention,control and treatment of the disease in the future.3 Sequencing and Analysis of the whole Genome of Streptococcus equis isolated from SheepThe whole genome of Streptococcus equis isolated from sheep was sequenced by Illumina Mi Seq high-throughput sequencing.The results showed that the total length of the whole gene of Streptococcus equi was2272497 BP,the content of Genec was 41.1%,and it was predicted to contain 2124 coding genes.The prediction results of RNA showed that the number of 5Sr RNA,16Sr RNA and 23Sr RNA was 5,the number of t RNA was 57,and 4 pre-changes were detected.4 virulence genes were also detected.