As World Health Organization (WHO) member states bang heads in Geneva over a pandemic agreement to keep the world safe, a group of scientists has challenged global decision-makers to pay far more attention to humans’ relationship with animals.

“Although preparedness and response have received significant focus, prevention, especially the prevention of zoonotic spillover, remains largely absent from global conversations,” write the 24 scientists from a range of different global institutions in an article in Nature Communications published on Tuesday (26 March).

Using bats as their case study, they show how environmental changes exacerbate zoonotic spillover – and identify the “ecological interventions that can disrupt these spillover mechanisms”.

Their ecological countermeasures focus on bats because a number of major epidemics and pandemics” – SARS-CoV-2, Ebola, SARS-CoV-1, MERS-CoV, and Nipah virus –  have an evolutionary origin in bats.

Certain bat species also host four of the nine diseases identified by the WHO as having the potential to generate epidemics that pose a great risk to public health.

So what does an ecological approach look like when applied to bats? The authors propose three measures to prevent zoonotic spillover from bats to humans.

The first involves protecting where bats eat, which involves numerous interventions including preserving and restoring vegetation diversity and structural complexity in bat foraging habitats.

In subtropical Australia, for example, Pteropus species bats (which carry the deadly Hendra virus) feed on nectar in winter-flowering forests. But in some areas, over 90% of these forests have been destroyed.

“Replanting winter habitats would be a sustainable, scalable, and effective strategy to reduce the risk of spillover of not just Hendra virus, but other viruses carried by Pteropus species bats,” they argue.

The second measure involves protecting where bats roost.

“Roosts are locations where bats sleep, shelter, mate, socialise, and raise their young. With few exceptions, bats cannot construct shelters and must roost in pre-existing natural (eg, caves, rock crevices, tree cavities, and tree foliage) or human-made (eg, buildings, bridges, mines) structures,” the authors state.

The third measure involves protecting people and their livestock who come into contact with bats. This can be done by reducing livestock’s interactions with bats and bat excreta and providing personal protective equipment for peoplein contact with bats or their excreta.

In Malaysia, for example, “a regulation requiring fruit trees to be planted at a distance from pig sties may explain the lack of subsequent Nipah virus spillovers”, the authors note.

Integrating ecological and biomedical approaches

“Recognising that pandemics originate in ecological systems, we advocate for integrating ecological approaches alongside biomedical approaches in a comprehensive and balanced pandemic prevention strategy,” they argue.

Pandemics almost always start with a microbe infecting a wild animal in a natural environment, but when a wild animal then infects a human, this is often triggered by “human-caused land-use change”. The more land use changes, the greater the risk of zoonotic spillover.

“Designing land management and conservation strategies to explicitly limit spillover is central to meeting the challenge of pandemic prevention at a global scale,” they argue.

“In our view, the most effective strategy to reduce the probability of another pandemic is to preserve intact ecosystems and bolster their resilience through restoration and the creation of buffer zones.

“Our primary emphasis should be on maintaining and enhancing the integrity and resilience of still-intact landscapes to prevent new interfaces that could enable the emergence of Disease X.”

Pandemic agreement and One Health

Article 5 of the draft pandemic agreement is devoted to One Health, which it defines as “an integrated, unifying approach that aims to sustainably balance and optimise the health of people, animals and ecosystems. It recognizes that the health of humans, domestic and wild animals, plants and the wider environment (including ecosystems) is closely linked and interdependent”.

According to the draft agreement, parties will commit to a One Health approach for pandemic prevention, preparedness and response that is “coherent, comprehensive, integrated, coordinated and collaborative among relevant actors and sectors”.

Proposed measures include engaging communities to prevent, detect and respond to zoonotic outbreaks; workforce training; updating international standards and guidelines, and developing multilateral mechanisms to help developing countries to adopt a One Health approach.

Image Credits: Chris Black/WHO.