Isolation and Characterization of a Highly Virulent Getah Virus Causing Acute Lethal Infection in Neonatal Piglets.

Getah virus (GETV) is a mosquito-borne alphavirus with an expanding host range and an increasing impact on swine production, particularly in neonatal piglets. In this study, a severe disease outbreak characterized by acute diarrhea and high mortality occurred among suckling piglets on a commercial pig farm in central China. Comprehensive pathogen screening excluded common bacterial pathogens and major enteric viruses, whereas GETV RNA was consistently detected in multiple tissues. A GETV strain, designated GETV-WH, was successfully isolated from lung tissue and propagated in BHK-21 cells, where it reproducibly induced pronounced cytopathic effects (CPEs). The isolate was confirmed by immunofluorescence assay (IFA) using a GETV E2-specific monoclonal antibody and further purified by plaque assays. Growth kinetics analysis demonstrated efficient viral replication, with peak titers exceeding 108 TCID50/mL at 24 h postinfection. Experimental infection of 5-day-old piglets resulted in rapid disease progression characterized by hypothermia, systemic viral dissemination, severe multiorgan lesions, and 100% mortality within 2 days postinoculation, indicating high virulence of the isolate in neonatal piglets. Complete genome sequencing and comparative analysis identified multiple amino acid substitutions relative to the reference strain MM2021, including two unique substitutions located in NSP1 and the E2 protein. Phylogenetic analysis based on complete genome sequences placed GETV-WH within genetic Group III, where it formed a distinct branch among contemporary Chinese strains. Collectively, these findings demonstrate that GETV-WH is a highly pathogenic GETV strain capable of causing acute systemic infection and lethal disease in neonatal piglets, highlighting the potential threat posed by highly virulent GETV variants to swine health.