Cases Analysis Of Feline Infectious Peritonitis In Wuhan And Isolation And Identification Of The Virus

Feline infectious peritonitis(FIP)is a chronic,progressive,fatal infection of felines caused by feline infectious peritonitis virus(FIPV).It is caused by peritonitis and massive ascites or granulomatous lesions in various organs and high mortality are the main clinical features.The disease is endemic in all parts of the world,and its high mortality rate has caused significant economic losses to the companion animal industry.Therefore,it is of great significance to carry out research on FIP pathogens,epidemiology,pathogenic mechanisms and preventive and therapeutic measures.The purpose of this study was to investigate the prevalence of FIP in Wuhan,Hubei Province.Based on the outpatient clinical cases of the Animal Hospital of Huazhong Agricultural University,1036 samples collected during the period of November 2017 to September 2018 were tested by means of Feline coronavirus rapid identification strips and RT-PCR,and the infection situation and characteristics of all cases were analyzed.According to the results,a total of 61 cases were tested positive for FIPV with the detection rate of 5.9%.In terms of time distribution,the positive rate in January of 2018 remained the highest,accounting for 13.4%,and the rates in other months were at the range of 6.0%~8.0%.In terms of population distribution,the positive rates of,British Shorthair and domestic cats were much higher,accounting for 63.9%.British shorthairs accounted for 41.0%,while domesticl cats accounted for more than 10.0%.Besides,the positive rate of male cats(70.0%)was obviously higher than that of female cats(30.0%),and the rate of kittens under 12 months was 72.1%.This study shows that the incidence of FIP in Wuhan,Hubei Province is closely related to cat breed,age and gender.In order to analyze the molecular epidemiological characteristics of current FIP-positive cats in Wuhan,this study isolated and identified the virus infected by clinical FIP cats.Twelve FCoV strains HN-1~HN-12 were successfully isolated from 12 positive samples,Five of them were randomly selected for S gene fragment analysis and phylogenetic tree analysis using MEGA6.0.Among them,4 strains belong to the FCoV I serotype and belong to the FECV(Feline enteric coronavirus)biotype.HN-6 strain forms a separate subpopulation.In order to further explore the molecular biological characteristics of the virulence-related genes 3c and 7ab of the isolated strains,this study amplified the 3c and 7ab of the 12 strains isolated,and construction of serotype and biotype phylogenetic tree for positive samples.3c serotype genetic phylogenetic tree analysis showed that 8 strains of them belonged to FCoV I,1 strain belonged to FCoV II,and 2 strains of them formed an independent subgroup.3c biotype phylogenetic tree analysis showed that 8 strains of them belonged to FECV,1 strain belonged to FIPV,and the remaining 2 strains formed an independent subgroup.Analysis of 7ab serotype phylogenetic tree showed that 3 strains of them belonged to FCoV I,2 strains belonged to FCoV II,and 4 strains of them formed an independent subgroup.The 7ab gene biotype phylogenetic tree analysis showed that 3 strains of them belonged to FECV,2 strains belonged to FIPV,and the remaining 4 strains formed an independent subgroup.Based on the serotype and biotype genetic evolution analysis of the S,3c,and 7ab genes of each strain,the serotypes of HN-1 and HN-8 strains belong to FCoV I,and other strains produce different results based on different genotyping.Different results indicate that phylogenetic tree analysis can determine its genetic evolutionary relationship,but cannot analyze its serotype and biotype.This study analyzed the molecular epidemic characteristics of FIP in Wuhan,laid a theoretical foundation for the prevention and control of feline infectious peritonitis in Wuhan,and provided assistance for the targeted development of clinical FIP vaccine.In summary: This study is based on the clinical epidemiological situation of the Animal Hospital of Huazhong Agricultural University in Wuhan from November 2017 to September 2018,and mastered the epidemiological characteristics of FIP in Wuhan,and isolated 12 FCoV strains.Based on its S,3c and 7ab genes,the phylogenetic analysis of serotypes and biotypes was constructed,and the molecular biological characteristics of 3c and 7ab were explored,which provided a theoretical basis for the prevention and treatment of the disease.