Epidemiological Investigation And Pathogenicity Of Enterovirus Infection In Sheep In Henan Province

Caprine/ovine enterovirus?CEV/OEV?infection is a new infectious disease reported at home and abroad.Its pathogen belongs to enterovirus genus of within the family of picornaviridae.In recent years,sheep in many areas of Henan Province have suffered from unknown diseases characterized by severe diarrhea and respiratory symptoms,which has brought great economic losses to the sheep industry.In order to determine the pathogen causing diarrhea in sheep in Henan Province,virus isolation and identification were carried out by virus isolation and culture,observation of cytopathic characteristics,electron microscope observation,TCID50 determination,physical and chemical characteristics identification,immunological identification,genetic identification and other technical methods The TCID50 of the three strains were 10^-8.50/0.1 ml,10^-8.76/0.1 ml and 10^-9.0/0.1 ml,respectively The results of biological,immunological and genetic characteristics of the three strains showed that the three strains were acid resistant,not sensitive to chloroform and ether,but sensitive to high temperature.The three strains had strong immunological reaction with CEV positive serum.The three strains were in the same branch of evolution tree as the goat enterovirus CEV-JL14 strain.The 5'UTR gene of the three isolates shared91.1%?95.1%homology with that of CEV-JL14 strain.The results showed that all the three isolates were new enterovirus,and sheep enterovirus infection existed in sheep in Henan Province.In order to determine the epidemiological background of CEV infection in Henan Province,a double antibody sandwich ELISA method was used to detect and analyze the etiology of CEV infection in fecal samples collected from different areas of Henan Province from 2015 to 2019.The results showed that the infection rate of sheep in different areas of Henan Province was 10.85%?33.65%,the positive rate of CEV increased significantly in the past two years?2018 and 2019?,sheep were more susceptible to CEV than goats,and the positive infection rate of captive rearing was higher than that of free range rearing.The results revealed the epidemiological background of sheep enterovirus infection in Henan Province,and provided an epidemiological theoretical basis for the formulation of comprehensive prevention and control measures of the disease in the future.The single infection of CEV and the mixed infection of CEV with BVDV,BDV and PPRV were analyzed.The results showed that the single infection rate of CEV in 403samples was 80.40%,and CEV/BVDV,CEV/BDV,CEV/PPRV,CEV/BVDV/BDV,CEV/BDV/PPRV infection types were 6.95%,4.71%,5.96%,1.24%and 0.74%,respectively.The results showed that there were single infection of CEV and mixed infection of CEV with BVDV,BDV and PPRV.The ZK/2018 strain of CEV was selected to experimentally infect lambs.The results showed that the morbidity and mortality of ZK/2018 strains in infected lambs by gastrointestinal,respiratory,and intramuscular injections reached 4/4 and 2/4,2/4and 0/4,4/4 and 0/4,respectively.The results also showed that the virus could be excreted via feces for at least 14 days.ZK/2018 strain could cause obvious histopathogical change including intestinal villi shedding,intestinal mucosal epithelial cells swelling,renal tubular epithelial cells granular degeneration,a large number of lymphocyte infiltration,significant necrosis and aggregation of lymphocytes,alveolar wall thickening,inflammatory cell infiltration,spleen cells in the red pulp area.Immuno-histochemistry assay results showed CEV antigen could be detected in intestine,kidney,lymph node,lung and spleen of lambs infected by ZK/2018 strain.In summary,three strains of CEV were isolated and identified in this study.The biological characteristics and genetic variation characteristics of CEV isolates were characterized.The epidemiological background of sheep enterovirus infection in Henan Province was revealed,and the pathogenicity of CEV epidemic strains was determined.These results laid a foundation for further study on pathogenic mechanism of sheep enterovirus and new vaccine research,and for Henan Province and even the whole country comprehensive prevention and control measures of sheep enterovirus provide a theoretical basis.