Molecular Epidemiology And Complete Genome Sequence Analysis On Porcine Teschovirus In Jiangxi Province

Porcine Teschen disease,caused by porcine teschovirus(PTV),is characterized by a variety of clinical symptoms including polio,reproductive disorders,pneumonia,diarrhea,pericarditis,and myocarditisin in pigs of all ages.PTV is a non-segmented,positive-sense RNA virus,belonging to the genus Teschovirus,the family Picornaviridae,the order Picornavirales.Pigs serve as natural hosts of Teschovirus.To date,13 serotypes of PTV were identified in pigs,including viruses in serotype 1 to serotype 12 from domestic pigs and serotype 13 from wild boars.The virulent strain of serotype 1 PTV(PTV-1)could cause severe polioencephalomyelitis in pigs,while the attenuated strains could lead to mild or letent infection.Thus,PTV-1 has been classified as the second-class infectious agent by the Organization for Animal Health(OIE).The disease caused by PTV in the early 20 th century in Europe has led to severe economic losses in the pig industry.However,there was limited information on the epidemiology and genome in PTV in China.In this study,a total of 934 samples from pigs with different ages collected in Jiangxi Province from Sept 2016 to Feb 2018 were tested.Of which,537 were fecal and intestinal samples,and 297 were brain,lung,and lymph nodes samples.A pair of specific primers for PTV was designed for the investigation of the epidemiology of PTV by testing aforementioned samples.The results showed that PTV was a common virus in farmed pigs in Jiangxi,and the positive rate of PTV in feces was as high as 49.5%,and the rate in brain,lung,and lymph nodes was 35.0%.The positive rates of PTV were different in pigs during different growing stages.The positive rate of suckling piglets was 22.34%,the lowest rate,and the rates in nursing and finishing pigs were 56.08% and 56.35%,respectively.Samples collected in winter and spring showed higher detection rates of PTV than that in summer and autumn.Co-infection of PTV with other diarrheal viruses was also observed,and the highest co-infection event was PTV and porcine epidemic diarrhea virus(PEDV),with a positive rate of 43.61%.In order to address the genetic variations of PTV in Jiangxi province,five pairs of PTV-specific primers were designed to amplify the full length of the genome sequence of PTV.To amplify the extreme end of the genome of PTV,two RACE primers were designed.Two representative strains of CH/JX/JA strain and CH/JX/JJ strain,sampled from Ji'an,Jiangxi Province and Jiujiang,Jiangxi Province,respectively,were amplified.Each amplified fragment was ligated into the pMD19-T vector and cloned and sequenced.Sequencing analysis was performed using SeqMan in the DNAStar Lasergene software package;genome-wide sequence similarity and phylogenetic tree analysis were performed using MEGA 6.05 and MegAlign from the DNAStar Lasergene software package.The total lengths of the CH/JX/JA strain and CH/JX/JJ strain were 7,107 nt and 7,098 nt,respectively.Homologous analysis of the two strains of the virus genes showed that the nucleotide homology between the two Jiangxi strains was 81.9%,and the homology between the two strains and reference PTV strains ranged from 80.5 to 91.4%.Compared with the reference strains,CH/JX/JJ and CH/JX/JA had different degrees of variation,the conservation of the genome sequences of of PTVs were relatively low,and there were also various variations among the genomes of the reference PTV strains.