Human deforestation activities link bats to Ebola outbreaks

Straw-colored Fruit bat (Eidolon helvum) in Lomé, Togo. Used under Creative Commons license. Stephen C. Smith

Deforestation may accelerate the spread of the deadly Ebola disease in the rainforests of West and Central Africa by increasing human-bat interactions, a new study shows.

Fruit bats (Pteropodidae) are suspected reservoir hosts for the Ebola virus (EBV), which is often fatal to humans and other primates.

Named for their dietary preferences, several large fruit bat species proliferate in fragmented rainforests or in agroforestry settings, according to research led by scientists with Spain’s University of Malaga (UMA) and the Center for International Forestry Research (CIFOR).

The research results published in Mammal Review journal, posit that when the flying frugivores are unsettled by human activities leading to deforestation, their habitats expand, increasing their contact with people and influencing the spread of Ebola.

Currently, the Democratic Republic of Congo is battling the second largest EBV epidemic on record, with more than 2,200 lives lost and 3,300 confirmed infections since the outbreak was declared in August 2018, according to data from the World Health Organization (WHO).

SWEET ATTRACTION

Forested areas are often cleared to plant fruit tree crops. Agricultural activities increase the number of people moving to areas where there is a greater food supply for bats, said John Fa, a senior associate scientist with CIFOR and a professor of biodiversity and human development at Britain’s Manchester Metropolitan University.

In turn, this could hypothetically increase the spread of Ebola.

“While heavily forested areas aren’t particularly conducive for dense populations of humans, when areas are opened for agriculture or other purposes, more people are going to be in the area,” he said. “This means the possibility and mechanism for infection is also going to be greater.”

In general, the bats also tend to live in open areas outside the forest canopy.

“Any forest areas opened up by humans are automatically going to be fairly attractive to bats because they can move around and look for food in these spaces and in marginal areas of the forest,” Fa said.

To undertake the study, scientists used maps they had previously created, and made a geo-referenced location database for 20 currently recognized African fruit bat species, whose distributions overlap with the Ebola virus area.

Their research led to biogeographical evidence supporting the hypothesis that deforestation could provide favorable conditions for five of the species to influence the nature of Ebola outbreaks.

PROTECTING BATS

“We still need to conduct further research, particularly to determine the relative scale of deforestation favoring the expansion of fruit bat populations,” said Jesus Olivero, a professor of biogeography and micro-ecology at UMA, cautioning that current findings do not provide a carte blanche to cull bats.

“As yet, we do not know the level of deforestation that will change the habits of bat communities,” Olivero said. “We need to determine if there is a tipping point beyond which catastrophic effects result.”

The consequences of eliminating fruit bats in a forest would be devastating, Olivero said, explaining that “the entire function and ecology of forests would be put at risk if these vital pollinators and seed dispersers are eliminated.”

It is crucial to explore all possible patterns that may explain Ebola outbreaks; we are not saying bats are the culprits or that we should eliminate fruit bat colonies, Fa added.

“Many unknowns still exist, including whether these bats are effectively the reservoir species carrying the disease without being affected by it themselves, but all the signs seem to point to that,” Fa said. “We need to gain clarity over whether increasing rates of deforestation can change the natural circulation of viruses and lead to a greater risk of the spread of Ebola.”

This study was supported by USAID as part of the Bushmeat Research Initiative of the CGIAR Research Program on Forests, Trees and Agroforestry, by the Spanish Ministry of Economy and Competitiveness and FEDER Funds.