Epidemiology: Changes to bat habitats facilitate the emergence of zoonotic viruses

Changes in climate and land use may be driving the spillover of pathogens from bats to other animals, a study in Nature suggests. An analysis of data collected in Australia reveals that scarcity of food and the loss of natural habitats contributes to the persistence of bats in populated areas, leading to spillover of Hendra virus (an emerging zoonotic disease) to its intermediate host, the horse. Understanding the connection between habitat loss, climate change and spillover risk could help in the development of measures to prevent future pandemics.

Zoonotic spillover is the transmission of a pathogen from animals to humans, often via an intermediate host. One such pathogen is Hendra virus, a bat-borne virus that mainly infects large fruit bats (Australian flying foxes). Hendra virus is not fatal to bats but can be transmitted to horses, the intermediate hosts from which the virus spills over into humans to cause severe or fatal disease. Previous research has indicated that land-use change may be linked to the spillover of viruses from wildlife to humans, but this new study provides detailed evidence of the mechanisms involved.

Peggy Eby, Raina Plowright and colleagues analyse 25 years of data (1996–2020) on land-use change, bat behaviour and spillover of Hendra virus from bats to horses in subtropical Australia. These data show that land-use change and climate are driving bats to live in agricultural and urban areas. Climatic factors such as El Niño events caused food shortages for bats, and these events preceded an increase in roosts closer to human-populated areas (which offer access to food). Similarly, the loss of natural bat habitats drove bats to roost closer to areas where humans live. Both of these factors were associated with a greater risk of Hendra virus spillover into horses. The authors note that the bats left agricultural and urban areas when there were periods of winter flowering in nearby remnant native forest (natural fruit bat habitats), and spillovers did not occur during these flowering periods.

These findings identify key processes that connect land-use change to spillover via the behavioural responses of bats to altered food availability, the authors note. Understanding the causes of virus spillover may guide efforts to mitigate bat-virus spillover, they conclude.