The warmer weather, extra rain showers and spring season signal the return of a not-so-popular pest in the U.S. Yes, it’s time for the annual surge in the mosquito population.
Pork producers are urged to implement robust control strategies to reduce mosquito populations near swine farms and minimize potential production impacts, the Swine Health Information Center (SHIC) points out in its recent newsletter. The changes in environmental conditions, specifically during high rainfall seasons, often result in increased mosquito populations that can be a risk for emerging disease and other swine production challenges.
Through global disease monitoring by SHIC, awareness for mosquito control stems from the recent 2025 re-emergence of Japanese encephalitis virus (JEV) in Australia. JEV, a mosquito-borne virus which has waterbirds as a natural reservoir host but is capable of infecting pigs, humans, and horses, can cause reproductive failure, delayed farrowing, stillbirths, mummified fetuses, abortions and weak piglets in swine breeding herds.
In February 2025, JEV was reported at two piggeries in southern Queensland, Australia, marking the first detections of the virus in Australia commercial swine since July 2022. Although no cases were detected in piggeries during 2023 or 2024, this re-incursion of JEV into Australian piggeries requires close monitoring, SHIC says.
Detections in mosquito populations more recently in Goondiwindi, Inglewood, and Monto, as well as in mosquito and feral pig populations in New South Wales, have raised concerns about further potential spread of JEV, particularly with wet season conditions increasing mosquito activity.
“The U.S. is currently negative for JEV,” SHIC reports. “In December 2024, SHIC, along with the Foundation for Food & Agriculture Research, funded six research projects to enhance U.S. prevention, preparedness, mitigation and response capabilities for JEV. Understanding the biology and lifecycle of mosquitos can aid in the development of mitigation and control strategies to reduce risks of pathogen transmission as well as improve swine health and welfare.”
Chris Rademacher, DVM and associate director of the Iowa Pork Industry Center, shared information with producers detailing mosquito control strategies in an August 2024 webinar hosted by SHIC.
“Effective environmental management includes diligent control of standing water, a breeding ground for larvae, and vegetation management around buildings, which serve as resting sites for mosquitoes,” Rademacher said. “Ventilation adjustments within barns can also play a crucial role in mosquito population control.”
He encouraged producers to consult with entomologists, who can offer expert pest identification and control strategies like site maintenance.
Site maintenance includes establishing rock barriers for proper water drainage around buildings, maintaining short grass, and controlling weeds around all production facilities. He urged producers to pay particular attention to curtain pockets, which can retain water. Operating stir fans at night during peak mosquito season in naturally ventilated barns and running tunnels at night in tunnel-ventilated barns can help mitigate mosquito populations within barns. Proper adjustment of misters, waterers and sprinklers is another important way to prevent water pooling in all barn types.
Chemical mitigation should be integrated into a comprehensive pest management strategy, with adult mosquito spraying considered the least effective component, SHIC says.
“Utilizing non-residual and residual sprays, with strict adherence to label instructions, is critical,” SHIC adds. “Fogging devices, employing oil or water-based pyrethrins, are recommended for adult mosquito infestations within buildings. Residual sprays should be applied to resting surfaces, not directly on animals. To mitigate resistance, rotating the mode of action groups of chemical mitigants is essential.”
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