Continued circulation of African swine fever virus Genotype II in Mizoram, India, 2023-2025: molecular and phylogenetic evidence.

African swine fever is considered to be one of the most important viral diseases affecting pigs worldwide as it leads to high morbidity and mortality. The first occurrence of ASF in domestic pigs in India was recorded in North-eastern states in early 2020. In mid- March 2021, the disease also reached the state of Mizoram, where it continues to pose a major threat to pig production. The present study investigated ASF cases in pigs from four districts of Mizoram including Aizawl, Champhai, Kolasib, and Mamit, during July 2023 to June 2025. A total of 105 pigs showing clinical signs suggestive of ASF or sudden death were screened using a rapid antigen test (RAT) and 54 cases were confirmed by polymerase chain reaction (PCR). Molecular characterization was performed by amplification and sequencing of partial p72 and p54 genes followed by phylogenetic analysis, and four representative sequences were submitted to GenBank. Out of 105 suspected cases, 41 were tested positive using RAT and 54 were confirmed positive for ASFV by PCR across all four districts. Sequence analysis of the p72 and p54 genes revealed high nucleotide identity with ASFV Genotype II strains reported from other states of India, Asia, and Europe. Phylogenetic analysis placed all Mizoram isolates firmly within the Genotype II lineage. The study provides molecular and gross pathological observations of the continued circulation of ASFV Genotype II in Mizoram during 2023-2025, highlighting the need for sustained molecular surveillance and strengthened biosecurity measures to control ASF in the region.