Conditions predict heightened Hendra virus spillover risk in horses this winter: actions now can change outcomes.

The research focuses on how specific environmental conditions can predict spillover of the Hendra virus from flying foxes to horses, thereby presenting an opportunity to mitigate the impact of such spillovers. The study strongly suggests that the winter season of 2020 will carry a heightened possibility for Hendra virus spreading.

Significance of Understanding Bat Virus Spillover

• As the COVID-19 pandemic is believed to have originated from a wildlife source, studying similar spillovers can provide useful insights into how to predict and mitigate such events in the future.
• Understanding the drivers of viral emergence from bat reservoirs has become particularly crucial to improve readiness against epidemics arising from such spillovers.
• While Hendra virus spillover from bats to horses has not resulted in human epidemics like coronaviruses, its periodic occurrence offers rich opportunities to study the causative conditions and help predict when these might occur.

Predicting Hendra Virus Spillover

• Through long-term datasets on flying fox ecology and climatic conditions, researchers have been able to predict periods of heightened Hendra virus spillover risk.
• The spillover events often coincide with periods when flying foxes, which are primarily nomadic nectar feeders, experience food shortages, specifically during moderate to severe El Nino winters.
• During these periods, bats tend to feed more on non-native fruit and nectar plants, and if infected bats feed and urinate on trees within horse paddocks, those horses become exposed to the virus.

History of Hendra Virus Spillover

• The largest recorded cluster of equine Hendra virus spillover events occurred in winter 2011, where 18 instances were reported after a chain of climate events – extreme El Niño (dry), strong La Niña (serious flooding), and an extensive food shortage for flying foxes.
• Similar conditions were observed in 2017, resulting in another series of spillover events. The researchers thus anticipate a similar risk for winter 2020 due to comparable climatic and ecological preconditions.

Impact of Bushfires on Predictability and Risk

• Unprecedented bushfires in 2019-2020 in eastern Australia have significantly depleted winter-flowering habitats, a critical food source for flying foxes.
• This impact on the bat’s ecology could increase the spillover risk in 2020 and the following years. Thus, further studies are needed to better comprehend bushfire implications for Hendra virus risk.

Preventive Measures

• Vaccination can greatly reduce the risk for horses. Since its introduction in 2012, the uptake of the Hendra virus vaccine appears to reduce spillover occurring in subtropical Australia.
• Increasing awareness about this risk among veterinarians and horse owners can encourage vaccination and instate safety measures, including proper usage of personal protective equipment.
• Tracking population changes due to vaccination as a result of this warning will aid in assessing the accuracy of predictions made by the researchers.