Molecular characterization and phylogenetic analysis of African swine fever virus from a pig farm in India.

Abstract

African swine fever (ASF) is considered as one of the most threatening diseases for the pig farming industry all over the world. Due to the lack of an effective vaccine, organized farms and backyard rearing must strictly enforce control measures in order to combat the disease. The present report describes the ASF epidemic in a piggery in Uttar Pradesh state, India. The pathological samples were collected from the affected pigs and processed for histopathological and molecular studies. Gross lesions comprised of cyanosis of ear pinna, multi-focal hemorrhagic spots on ventral abdomen and inner aspect of thigh, highly congested mesenteric lymph nodes with marbling, marked congestion, hemorrhages and splenomegaly, interstitial pneumonia, and multi-focal endocardial hemorrhages on papillary muscles and wall of ventricle in heart. Histopathological investigation revealed marked congestion and hemorrhages of mesenteric lymph node, liver and spleen. Depletion of lymphocytes from the splenic white pulp was visible in the splenic parenchyma. The virus was confirmed by polymerase chain reaction and phylogenetic analysis revealed a distinct clustering of the Uttar Pradesh virus isolates from Vietnam with other Ib group isolates, indicating a close genetic relationship between these samples. Additionally, the mutant Chinese virus isolate showed clear genetic differences with the Vietnamese Ib group, confirming its suitability as an out-group for comparison. The study represents the first report of ASF outbreak in North India, establishing the phylogenetic relationship between ASF virus circulating in the study area and other regions.