The Effect of Diurnal Temperature Fluctuations on the Decay of Japanese Encephalitis and Murray Valley Encephalitis Virus RNA Seeded in Piggery Wastewater

Japanese encephalitis virus (JEV) and the Murray Valley encephalitis virus (MVEV) are mosquito-borne pathogens capable of transmission from animals to humans, causing significant economic and public health impacts in affected countries. Pigs serve as amplifying hosts for JEV and potentially play a role in the natural ecology of MVEV. Reports of JEV viral shedding underscore the prospect of wastewater surveillance for early detection and intervention for animal and human health. To assess the feasibility of wastewater surveillance, the decay rates of JEV and MVEV RNA were determined under the simulated diurnal temperatures in summer and winter by seeding these viruses in piggery wastewater collected from three potential surveillance sites (shed, pit, and lagoon). During a 52-day experiment, a one log₁₀ reduction in RNA copies was found for JEV within 24.8–36.4 days, while MVEV experienced a 90% reduction ranging from 15.5 to 24.4 days, which was significantly faster than that of JEV. Seasonal temperature and site-specific differences significantly influenced the RNA decay rates of both viruses in piggery wastewater samples. These data indicated the sufficient persistence of JEV and MVEV under diurnal temperatures in summer and winter conditions, which would facilitate surveillance of viruses in piggery environments.