Veterinary and industry perspectives on the emergence of Japanese encephalitis in Australian swine herds.

In 2022, Australia experienced an unprecedented outbreak of Japanese encephalitis virus (JEV) across four states, resulting in seven human deaths. Occurring during a significant La Niña period, the event posed major challenges for detection and response across human and animal health sectors. This study explores the experiences of frontline veterinary and industry professionals to understand the operational and biological challenges encountered. We conducted a qualitative epidemiological study with 15 swine veterinarians, industry professionals and medical entomologists directly involved in the response, using thematic analysis to explore outbreak dynamics, perceived risk factors, and decision-making under uncertainty. Participants described marked heterogeneity in disease presentation, severity, and duration. Transmission was perceived to be vector-mediated and shaped by environmental and farm-level factors, with no field observations supporting direct pig to pig transmission. A key biological challenge was the delay between infection and clinical recognition in swine. On-farm mitigation focused primarily on mosquito control to reduce exposure in high-risk animals. Constraints included uncertainty regarding local transmission ecology, systemic surveillance gaps, limitations of diagnostic tests and the absence of a swine vaccine. Knowledge sharing and the need for adaptive, evidence-informed government responses were seen as important. These findings illustrate how climate-sensitive, vector-borne zoonoses challenge outbreak response frameworks, and demonstrate how integrating veterinary field observations and industry experience into One Health surveillance and response planning can strengthen preparedness for emerging vector-borne diseases in regions with commercial swine industries.