Pathology and molecular diagnosis of first African swine fever outbreak in Meghalaya

Abstract

African swine fever is one of the most devastating, contagious viral diseases of domestic and wild pigs. Mortality in pigs following acute fatal course of disease was investigated in pig population of Meghalaya, India. The affected animals showed severe depression, inappetence, lethargy, high fever, purplish discolouration of the skin to cutaneous haemorrhages and death within 3-4 days following onset of clinical signs. Detailed post-mortem examination in affected pigs revealed cutaneous haemorrhages, swollen dark black coloured haemorrhagic regional lymph nodes, haemorrhagic enteritis with blood mixed intestinal content, swollen and haemorrhagic spleen, petechiations in kidney, non-collapsing oedematous lungs with areas of haemorrhage and haemorrhagic myocarditis. The consistent microscopical lesion observed included necrosis and depletion of lymphoid tissues, haemorrhagic interstitial pneumonia, hepatitis and haemorrhagic tubular degeneration in kidneys. The 478 bp region of the p72 gene of ASFV was successfully amplified by polymerase chain reaction of DNA from tissue lesions, which has confirmed the outbreaks as ASF. Further the phylogenetic analysis of p72 gene sequence has identified the circulating strain as the ASFV genotype II. This study reports outbreaks of ASF as the major cause of pig mortality in five districts of Meghalaya during the period from April to November 2021.