Study Of Pathology,Isolation And Identification And Genetic Evolution Of Important Genes Of Virus Of Equine Rhinopneumonia

Equine rhinopneumonia is an infectious disease caused by equine herpesvirus type 1(EHV-1)and equine herpesvirus type 4(EHV-4)characterized by abortion and pneumonia in equine animals,and is one of the infectious diseases of equine animals that must be quarantined at entry and exit in China.Equine rhinopneumonia is found in countries around the world and has a large impact on the development of the equine industry.In this research paper,a pathological study of an aborted foal with equine rhinopneumonia was conducted by clinical history,necropsy and histopathological methods.Equine herpesvirus was isolated and identified from the liver and spleen of the aborted foal by MDBK cell culture and PCR,and finally the gB,gC,gD,gE,gG,gI,gM,ORF30 and ORF37 genes were obtained by specific PCR and sequencing,and genetic evolutionary analysis was performed.The results showed that the aborted dead foal was well developed,the abdominal cavity was filled with blood-like ascites,and the fatty tissue around the subcutaneous and internal organs of the body was severely edematous in the form of yellowish transparent jelly.There were scattered gray-white lesions of corn size on the surface of the liver,scattered hemorrhagic spots of varying sizes on the surface of the spleen,epicardium,pulmonary pleura,and skull surface,and diffuse necrosis on the cut surface of the right ovary.Histopathological manifestations of necrotizing hepatitis,interstitial pneumonia,necrotizing ovaritis,necrotizing lymphadenitis,and necrotizing splenitis.Foci of necrosis of variable size were scattered in the liver tissue,diffuse areas of necrosis were seen in the ovarian cortex and medulla,diffuse necrosis of lymphocytes in the lymph nodes,focal necrosis in the white marrow of the spleen,and typical eosinophilic viral inclusion bodies were seen in the nuclei of hepatocytes at the margins of the necrotic foci in the liver,in the nuclei of reticulocytes in the necrotic foci in the lymph nodes,and in the nuclei of localized fine bronchial epithelium.Homogenates of liver and spleen tissues inoculated with bovine kidney cells for48 h showed typical cytopathic lesions such as cell rounding,fusion,shedding and clustering into grape bunches,which were identified by specific PCR as an equine herpesvirus type 1strain,named strain EHV-1-NM2021.The multigene genetic evolution results showed that the gB,gC,gD,gE,gG,gI,gM,ORF30 and ORF37 genes of the isolated strain EHV-1-NM2021 had the highest homology with the reference strains from Europe,America and East Asia and were located within the same genetic evolutionary branch,which led to the hypothesis that the study strain was most closely related to the strains from these regions and probably originated from a common ancestor.The research results can lay the foundation for the pathological diagnosis,in-depth pathogenic research and vaccine development of equine nasal pneumonia in Inner Mongolia.