| Hepatitis E virus(HEV)is an important zoonotic pathogen that can infect a variety of animals such as humans,pigs,cattle,sheep,rabbits,poultry and rodents,and sick pigs usually present asymptomatic and can be used as a source of infection for humans.Tibetan pigs are the only pig breeds growing in high altitude areas of China,mainly free-range grazing,which is widely popular because of its excellent quality and is one of the industries revitalized by rural areas in Tibetan areas.With the continuous expansion of breeding scale,the occurrence and prevalence of infectious diseases have gradually become a factor restricting the development of Tibetan pigs,of which hepatitis V,as an important zoonosis,poses a threat to public health and safety.In recent years,there have been not many studies on HEV in Tibetan pigs.In order to understand the prevalence and genetic evolution characteristics of HEV in Tibetan pigs in Ganzi Prefecture,205 diarrhea and healthy fecal samples of Tibetan pigs collected from 6 Tibetan pig farms in Ganzi Prefecture were detected for HEV and common intestinal pathogens.After genotyping the HEV positive strains,typical strains were selected for whole gene amplification and genetic evolution analysis.The results are as follows:1.In order to understand the prevalence of HEV in Tibetan pigs in Ganzi Prefecture,diarrhea and healthy fecal samples were collected from Tibetan pigs in 6 Tibetan pig farms in 5 counties of Ganzi Prefecture,and porcine HEV was detected by nested PCR,and the mixed infection of common enteropathogens Salmonella,porcine rotavirus(Po RV),porcine epidemic diarrhea virus(PEDV),porcine Delta coronavirus(PDCo V)and transmissible gastroenteritis virus(TGEV)was detected by RT-PCR,and the HEV genotypes and molecular characteristics of positive samples were also identified by genetic evolutionary tree and homology analysis.The results showed that HEV was detected in all6 Tibetan pig farms,and the overall positive rate of samples was 14.6%,in which the positive rate of diarrhea samples was 26.4% and the positive rate of healthy samples was8.3%.There was very significant difference between the two groups(P<0.01).The genotype was determined to be HEV-4a by genetic evolutionary tree after sequencing the PCR products,with the highest amino acid identity(98.5%-100.0%)to the representative strain of HEV-4.In summary,it can be seen that the prevalence of HEV in Tibetan pigs in Ganzi Prefecture is high,and the harm to the breeding industry needs to be evaluated.At present,HEV-4a is one of the main genotypes infecting humans in China,and the harm to local public health and safety deserves high attention.2.In order to further study the genomic characteristics of HEV in Tibetan pigs in Ganzi Prefecture,four representative strains were selected from the positive strains,and 10 pairs of primers were designed for segmental amplification,followed by splicing and assembly with Seqman software,homology analysis with Meg Align software,and genetic evolutionary tree establishment with MEGA 7.0 software to understand genetic evolution.The results showed that the target fragment was amplified this time.After splicing and assembly,it was proved that 4 strains of approximate complete gene sequences containing complete coding regions were obtained.The nucleotide identities between the 4 strains were 89.5-94.5%,with the highest nucleotide identities with genotype 4(82.8%-98.3%)and 72.8%-75.8% with genotype 1,genotype 2 and genotype 3.There were a total of 32 amino acid sense mutations in the 4 strains,which were randomly distributed in the 3coding regions.The significance of the mutations remains to be discussed.In summary,four genomes were obtained in this study,the structure was solved,and the genome of HEV was enriched,providing valuable scientific basic data for in-depth understanding of the study of HEV and the prevention and control of this zoonotic pathogen. |
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