| Canine distemper(CD)is an acute and highly contagious disease caused by canine distemper virus(CDV).It can cause a variety of host infections such as canine,mink,raccoon and so on.CD is distributed all over the world,which is highly contagious and easy to co-infection and secondary infection of other pathogenic microorganisms with more than 80% of mobidity.It has become one of the important diseases affecting the health of pet dogs,wild animals,fur economic animals and some marine animals,and brought serious economic losses to the society.With the improvement of pet owners’ level of feeding,management and the enhancement of awareness of prevention,the epidemic has gradually changed from mass,frequent and pandemic to sporadic.In this study,we investigated the clinical incidence of CD and the genetic evolution of partial N gene and H gene in some areas of Guangxi in the past three years for undestanding the incidence regularity and epidemic characteristics of CD in pet dogs which provide important theoretical support for the prevention and control of CD in future.In this study,917 cases of CD disease confirmed by clinical diagnosis and colloidal gold test strip in some areas of Guangxi from September 2016 to September 2019 were collected for retrospective study and analysis.The results showed that the proportion of CD in the number of clinical infectious diseases in dogs was 24.13%,13.20% and 20.70% respectively in the three statistical cycles,with an average of 18.80%,indicating that CD is prevalent in pet dog breeds to a certain extent.CDV showed a downward trend year by year,and the onset time was concentrated in winter and spring,especially from December to April.CD can occur in different ages,genders,breeds and body types,but the incidence of puppies aged from 2 months to 12 months is higher than the other ages,which reached to 81.89%.In order to further understand the genetic evolution of CDV in Guangxi,the partial N gene and H gene of some strains were amplified by RT-PCR.It was found that 5 of N gene and 3 of H genes were all in the same branch with Asian type 1(Asia-1)representative strain.The homology of partial N and H gene between them was 91.7%-99.2% and 97.6%-99.7%.Among these sequences,the GXNN20160508 strain shared 100% nucleotide homology with fox strain(LN(10)1)from Liaoning Province,China,suggesting that the outbreak of CD may be caused by wild animal infection.The results of genetic evolution analysis of some N genes showed that the wild strains GXLZ20190729 and GXNN20160207 were closely related to the northeast strain and were in the same branch.The two strains of GXNN20170528 and GXNN20160513 are in a small branch with Liaoning strain,Beijing strain and Heilongjiang strain.GXNN20160508 is in another small branch with Changchun strain.The results of genetic evolution analysis of some H genes showed that GXNN20160508 and GXNN20160513 strains obtained in the same year had close genetic relationship and were divided into a small branch with Thai strain.The results showed that all the strains in this study were Asian type 1,and there was genetic diversity among different strains.To sum up,the epidemic trend and clinical infection of CDV in Guangxi in the past three years were analyzed,which provided an important reference for the prevention and control of CD and the use of vaccine by understanding their genotypes through genetic analysis. |
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