Fruit bats blamed for Ebola outbreaks

Researchers have found strong evidence that fruit bats are responsible for outbreaks of the deadly Ebola virus in people.

Their findings — the latest in a decades-long effort to learn where the Ebola virus lives when it is not causing deadly disease outbreaks  — will be published tomorrow (1 December) in Nature.

Ebola causes a fever that kills 50 to 90 per cent of infected people. Since the first recorded human outbreak in 1976, researchers have tried unsuccessfully to find the virus's 'reservoirs' — one or more species it can survive in without causing symptoms.

Identifying these reservoirs could help scientists devise ways to prevent the virus from infecting people.

To find them, a team led by Eric Leroy of the International Centre for Medical Research in Franceville, Gabon, set traps near where Ebola had killed gorillas and chimpanzees in the Democratic Republic of Congo and Gabon.

They caught 1,030 animals, including bats, birds and rodents, and found evidence of the Ebola virus in three fruit bat species. None of the bats had symptoms of disease.

This, says Leroy, is the very definition of a reservoir species. "Too many things point to the bat as a reservoir species to continue doubting it," he told SciDev.Net.

Previous research has shown that captive bats infected with Ebola do not show symptoms. Bats are also known to be reservoirs for several other viruses including rabies, Nipah, Hendra and SARS.

Andy Dobson of Princeton University, United States, says understanding why bats are so good at withstanding viral infections could help scientists control viruses in people and livestock.

Dobson suggests studying how the DNA of bats and other mammals affects their ability to fight disease. "We need to know whether and why [this is different] in bats as it could lead to great breakthroughs in treatments for viral disease of humans," he told SciDev.Net.

Leroy and colleagues noted that Ebola sometimes kills more apes in the dry season, when forest fruit is scarce. This might be due to more contact between the apes and fruit bats as they compete for food.

Knowing that bats are a reservoir for Ebola, says Leroy, means that public health specialists can consider what measures need to be taken to limit future outbreaks.

He adds that warning local populations about the risk of capturing and eating bats is an important starting point.

Link to full paper in Nature

Reference: Nature 438, 575 (2005)