Investigation On The Etiology Of Feline Coronavirus In Partial Regions Of Northeast China

Feline coronavirus(FCoV)is a highly contagious virus that is prevalent all over the world.According to its pathogenicity,it can be divided into two biotypes: FECV and FIPV.FECV exists only in the digestive tract of cats,increasing by body temperature,loss of appetite,dehydration and other symptoms,but the fatality rate is low.Infection with FIPV can cause acute and severe inflammation in the peritoneum of cats,and the fatality rate is very high.FCoV has two serotypes: FCoV I and FCoV II.There are some differences in the sequence of gene S between them.The prevalence of FCoV I is higher,but it is difficult to replicate in vitro.The prevalence of FCoV II is low,and it is relatively easy to culture in vitro,so it is the main material to study FCoV.At present,there is no relevant vaccine,no specific treatment for this kind of virus,which seriously affects the health of pet cats.The number of pet dog and cat breeding in the Northeast of China is relatively large,but the investigation and research on FCoV is relatively few,and the prevention and control of FCoV is not paid enough attention,which poses a threat to the health of pet cats.Therefore,this paper analyzes the epidemic and genetic evolution of FCoV in some regions of Northeast China,in order to provide useful reference for the prevention and control of the disease.In this experiment,331 cat feces and ascites samples are collected from 9 cities in Northeast China from 2017 to 2020.the nested PCR method is used to detect FCoV.At the same time,the basic information of each sample is collected and recorded,which is divided into 7categories,including season,region,age,sex,breed,clinical health status and living mode.The distribution of positive rate is counted,and the correlation between each influencing factor and FCoV infection is analyzed by SPSS software.The results shows that the positive rate of FCoV infection in some regions of Northeast China is 29.3%(97/331),and age(p=0.003)and living mode(p=0.003)are significantly associated with FCoV infection.In this study,the gene S fragments of 97 FCoV positive samples are amplified and sequenced by nested PCR,which can distinguish FCoV serotypes.The results of nested PCR shows that the target gene is successfully amplified in 15 samples,and the size of the amplified products is 360 BP.The serotypes of 15 samples are determined to be FCoV I type.The nested PCR product is used to construct the recombinant plasmid and sequenced to obtain the gene S fragment sequence to construct the phylogenetic tree.The results shows that the gene S fragments of all samples are located on the FCoV type I branch,and 15 FCoV samples are further proved to be FCoV I.In terms of genetic relationship,it is relatively close to the domestic Harbin strain,and the foreign Swiss strain and Korean strain.To sum up,the research systematically investigatesthe epidemic characteristics of FCoV and the influencing factors of FCoV infection in some regions of Northeast China,analyzes the genetic evolution of FCoV S gene fragments and clarified the epidemic and genetic evolution of FCoV in some regions of Northeast China,which provided a reference basis for the prevention of FCoV and follow-up research.