Bat-borne zoonoses: climate change and biodiversity loss are reshaping spillover risk

Climate change, biodiversity loss and land-use change are altering where bats live, how they interact with humans and domestic animals, and consequently where zoonotic spillover may occur. A new review argues that prevention must move beyond outbreak response and address the ecological conditions that increase opportunities for transmission.

The review examines the major bat-associated zoonoses of public-health importance: Ebola, Marburg, Nipah, Hendra, rabies, Australian bat lyssavirus and histoplasmosis. Transmission pathways differ, but most involve exposure to infected bats, their body fluids or excreta, contaminated environments, or intermediate animal hosts.

Domestic animals can become epidemiological bridges

Several of the reviewed infections demonstrate the importance of the animal–human interface.

For Nipah virus, transmission can occur directly from bats or through infected animals, with pigs playing a major role in the Malaysian outbreak. Human-to-human transmission is also documented.

For Hendra virus, flying foxes are the natural reservoir, but horses act as the key intermediate host for human infection. Transmission to horses is thought to occur through contamination of feed or pasture with bat secretions or excreta, while human cases have followed close contact with infected horses.

Rabies illustrates another complex wildlife–domestic animal interface. Globally, dogs cause more than 95% of human rabies cases, but bats and other wildlife can maintain sylvatic cycles and repeatedly reintroduce infection into domestic populations.

Bats are important reservoirs, but not the enemy

The authors stress that bats provide essential ecosystem services and that disease prevention should not rely on indiscriminate bat control. Instead, risk reduction should focus on reducing opportunities for contact, protecting livestock feed and housing, improving farm biosecurity, preventing human exposure to bats and bat-contaminated environments, and using vaccination where available.

Vaccines currently exist for human rabies and Zaire ebolavirus, while Hendra vaccination is available for horses. For several other bat-borne diseases, including Nipah and Marburg, vaccine development remains under way.

Prevention must start upstream

The review’s broader message is ecological. Habitat loss, agricultural intensification and urbanisation can push bats into landscapes where interactions with livestock and people become more frequent. Climate change can also alter bat abundance and geographical distribution. The authors therefore argue that zoonotic preparedness should combine conventional surveillance, vaccination and outbreak control with better ecological stewardship and land-use policies designed to reduce risky interfaces before spillover occurs.

Preventing the next bat-associated zoonosis requires protecting not only human and animal health, but also the ecosystems that determine when and where those species meet.