Epidemiological Investigation Of Horse Chlamydiosis In Some Regions Of Northwest China

Chlamydiosis is a zoonotic disease caused by various types of Chlamydia.The clinical symptoms of animals are bronchitis,pneumonia,miscarriage and mastitis in female animals,seminal vesiculitis in male animals and calf death.At the same time,Chlamydiosis usually does not exhibit typical clinical symptoms in the early stage and presents latent infection.Failure to detect and intervene in drug treatment in a timely can lead to losses in the later stages of maternal and fetal life.Therefore,understanding the prevalence of Chlamydiosis in the region and formulating a comprehensive prevention in advance is important for the prevention of Chlamydiosis.As a new breed industry,horse breeding industry has become increasingly prominent in the cultural and economic fields in recent years.Gansu Province and its surrounding areas are the main horse breeding areas in China.However,the public’s attention to equine Chlamydiosis are extremely lacking,and the incidence of infection is rarely reported.There is no epidemiological investigation report of equine Chlamydiosis,making it difficult to accurately formulate prevention and control measures in clinical practice.This experiment was conducted against the background of the above situation.A serological detection method combining IHA and ELISA,as well as molecular biological detection methods combining fluorescence quantitative PCR and ordinary PCR,were used to investigate the prevalence of Chlamydia infection,analyze the homology and genetic evolution relationship between the endemic strains and the reference strains,and attempt to isolate the Chlamydia strain from the sample strains in chicken embryos.The specific research results are as follows:1.Using IHA and ELISA to detect Chlamydia antibodies in 2500 horse serum samples from Gansu and Xinjiang regions,the results showed significant regional distribution characteristics.The results of IHA showed that the positive rate of Chlamydia in the region was 4.68%,horses in Ili region of Xinjiang Province being the most severely infected,with a positive rate of 34.00%,The positive rates of Chlamydia in Tianzhu and Shandan regions of Gansu Province are relatively low,being 4.10%and 0.50%;The positive rate of C.abortus in horses in the region was slightly lower than that of Chlamydia,which was 4.24%,indicating that the region’s horses were mainly infected with C.abortus.The highest positive rate of C.abortus infection in horses in Ili was 50.00%,significantly higher than the positive rate in Tianzhu and Shandan regions of Gansu(50.00%vs.1.45%;50.00%vs.0.50%).2.Using quantitative real-time PCR to detect the family Chlamydia and 8 main pathogenic species of Chlamydia.A total of 576 samples were collected from Gansu Province,and the overall positive rate of Chlamydia infection was 47.09%(267/567).C.abortus is the main type of Chlamydia infection in Gansu Province.A total of 4 positive species were detected in 8 species of Chlamydia,including C.abortus(64.42%,172/267),C.psittaci(16.48%,44/267),C.felis(14.98%,40/267),and C.pecorum(8.99%,24/267).There were multiple samples infected with 2～4 species of Chlamydia simultaneously.In the four sampling areas,horses in Shandan and Shimen have the most severe Chlamydia,with 77.73%and 77.55%,while horses in Maqu have the lowest infection rate of 4.00%.Feeding mode is one of the important social factors for the prevalence of Chlamydia equi.The positive rate of Chlamydia infection in house fed is as high as 74.21%,significantly higher than that in grazing horses(74.21%vs 12.45%).3.Homology comparison and Isolation of Chlamydia strains.The positive samples for Chlamydia sequencing are highly homologous to the 16S rRNA and 23S rRNA sequences of C.abortus and C.buteonis,respectively.A live strain of Chlamydia was successfully isolated in the chicken embryo inoculation experiment.The 16S rRNA,23S rRNA,and ompA genes were amplified and analyzed for genetic evolution.The results showed that the isolated strain was classified as C.abortus,indicating that it was C.abortus.In summary,this study is the first to reveal the prevalence of Chlamydia in Gansu and Xinjiang regions in northwest China from the perspective of serology and molecular biology.It is clear that there are multiple mixed outbreaks of Chlamydia infection in horses in Gansu and Xinjiang regions,and the phylogenetic relationship between endemic strains in the region and reference strains is clear.And successfully isolate C.abortus strains from horse fecal samples.This study provides a reference basis for the prevention and control of Chlamydia in the horse breeding industry in Gansu and Xinjiang regions,and provides material support for the development of Chlamydia vaccines and drugs.