| Porcine deltacoronavirus(PDCoV),porcine epidemic diarrhea virus(PEDV),porcine rotavirus(PRo V)and porcine transmissible gastroenteritis virus(TGEV)are common porcine diarrhea-like viruses in recent years.Their clinical symptoms are very similar,which can cause watery diarrhea,vomiting,anorexia,dehydration and other symptoms in pigs.PDCoV is a newly discovered virus that can cause viral diarrhea in pigs in recent years.Compared with sows,piglets have higher morbidity and mortality,and it has been found that the disease is co-infected with other porcine intestinal viruses,which not only brings serious economic losses to the breeding industry,it also brings some difficulties for scientific prevention and control of PDCoV.At present,there are few studies on the pathogenic mechanism of PDCoV at home and abroad,and the understanding of the disease is not comprehensive enough to effectively prevent and control PDCoV.,Therefore,it is of great significance for the prevention and control of PDCoV to carry out local epidemiological studies and molecular genetic evolution analysis of the virus.1.Epidemiological investigation of major porcine diarrhea pathogens diseases in Guangxi from 2017 to 2019.In order to investigate the prevalence of major porcine viral diarrhea pathogens in Guangxi from 2017 to 2019,clinical samples of tissues,intestinal contents and anal swabs were collected from sick and dead pigs from different areas in Guangxi.PDCoV,TGEV,PEDV and PRo V were detected by multiplex RT-PCR.The results showed that PDCoV,PEDV,TGEV and PRo V positive rates were 5.67%(83/1463),10.12%(148/1463),1.30%(19/1463)and 5.95%(87/1463),respectively;the co-infection rates of two pathogens and three pathogens were 5.26%(77/1463)and 1.64%(24/1463),respectively;and the co-infection rate of PDCoV and PEDV was the highest up to 2.32%(34/1463).The results indicated that the infection of PDCoV,PEDV,TGEV and PRo V was very common in pig herds in Guangxi province,while mixed infection was serious.It should be further strengthened for pathogen surveillance and comprehensive prevention and control of these viruses.2.Genetic diversity of porcine deltacoronavirus in Guangxi province from 2017 to 2019To understand the genetic diversity of porcine deltacoronavirus(PDCoV)in Guangxi,diarrhea samples were collected from suspected piglets from 2017 to2019 in Guangxi.The clinical samples were detected by RT-PCR for PDCoV,and randomly selected positive samples for amplification and sequence of S,M,N genes.Finally,16 S,M and N gene sequences of PDCoV were obtained.The nucleotide and amino acid homology analysis showed that PDCoV S,M,N genes among Guangxi strains were 95.8%-99.9% and 91.5%-99.5%,95.9%-100% and 92.2%-99.5%,97.9%-99.9% and 97.1%-100%.The nucleotide and amino acid identity of S,M and N genes among Guangxi strains and reference strains were 95.1%-100% and 90.6%-100%,95.0%-100% and91.7%-100%,96.3%-99.9% and 93.6%-100%,respectively.Sequence alignment showed that S1 protein existed amino acid mutations and insertions,and there were some variations among different epidemic strains.Phylogenetic trees were established in the based of S,M and N genes and all strains could be divided into Group I,Group II and Group III,of which Group I came from USA,Japan and Korea,Group II came from China,and Group III came from China,Vietnam,Laos and Thailand.Most strains from Guangxi distributed in Group I,other strains distributed in Group III,and some strains formed a single small branch.The PDCoV S,M and N genes evolutionary rates of Guangxi strains and reference strains were 2.57×10-4,2.07×10-4,1.70×10-4 s/s/y,showing that the evolutionary rate of S gene is the fastest.The results indicated that PDCoV strains from Guangxi province had some variations and existed genetic diversity,which provided fundamental data for prevention and control of PDCoV. |
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