Dissection of the 'Virgin-soil' epizootic of African swine fever in Mizoram, a Northeast state of India

Abstract

This article aims to analyse the first-time emergence of African swine fever (ASF) in Mizoram. We collated the outbreak data and identified the time and locations of ASF emergence. To understand the impact of the outbreak, we have calculated the morbidity rate, mortality rate, case fatality rate (CFR) and overall pig depopulation rate. We identified that ASF emerged in total 178 locations in all 11 districts of Mizoram between March-July 2021, after a peak in June, and the disease continued to spread till the end of 2021 before re-emergence in March 2022. The overall morbidity rate and mortality rate of ASF between March-July 2021 in Mizoram were estimated to be 33.8% and 31.1%, while the average morbidity rate and the mortality rate of 10 districts were found to be 29.5% and 27.6% respectively. Overall CFR of ASF between March-July 2021 was estimated to be 92.1% and the average of all 11 districts was found to be 96.1%. Toward the end of 2021, the mortality rate increased by a total of 42.7% change and an average of 25.3% change. We estimated an overall 70% depopulation of susceptible pigs by disease and culling by end of 2021. This report is evidence that ASF has remained catastrophic and, keeping in view the complex nature and history of the virus on genotype adaptability associated with a high propensity for transboundary expansion, the virus continues to be a threat.