Poster Presentation 14th Lorne Infection and Immunity 2024

Seroprevalence and risk factors of flavivirus infections in horses in South-East Queensland post Japanese encephalitis virus incursion (#156)

Nicholas Yuen 1 , Althea Wang 1 , Jessica Harrison 2 , Gervais Habarugira 2 , Mitchell Coyle 3 , Helle Bielefeldt-Ohmann 2 4
  1. School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia
  2. School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia
  3. Equine Unit, Office of the Director Gatton Campus, The University of Queensland, Gatton, QLD, Australia
  4. Australian Infectious Diseases Research Centre, The University of Queensland, St. Lucia, QLD, Australia

Introduction

Mosquito-borne flaviviruses, including Japanese encephalitis virus (JEV), Murray Valley encephalitis virus (MVEV) and West Nile virus (WNV), present a growing threat to animal and human health in Australia. The recent emergence of JEV in Australia following extended periods of substantial rainfall due to the La Niña weather event prompted an update into the seroprevalence of flaviviruses and better understanding of the influence of meteorological conditions on flavivirus circulation.

Methods

Serum samples collected from a South-East Queensland mare and foal populations between 2020 – 2023 were tested in a pan-flavivirus blocking-ELISA. Positive samples were further subjected to testing for JEV, MVEV and WNV-specific antibodies. Cox proportional hazards analysis was applied using two approaches to determine if the meteorological variables, daily and cumulative rainfall, relative humidity and air temperature are associated with flavivirus seropositivity.

Results

Serological testing revealed JEV was the most prevalent of the three flaviviruses tested for in both mares (63.7%) and foals (61.5%), followed by MVEV (9.1% and 26.9%, respectively) and WNV (0% and 11.5%, respectively). The highest number of seroconversions were observed in 2022 in foals, peaking between March and May. Significant hazard ratios (p < 0.05) were identified for air temperature, relative humidity, and cumulative rainfall. In addition, air temperature with time-lag effect was significantly associated with reduced hazard ratio.

Conclusion

Our findings indicate the significance of meteorological conditions on flavivirus seroconversions in horses and demonstrate seroprevalence to JEV for the first time in South-East Queensland horses.