Until recently, five ebolavirus species were known, with three of these – Bundibugyo, Sudan and Zaire ebolaviruses – associated with large human outbreaks. The latter is responsible for the devastating 2013-16 outbreak in West Africa and the ongoing outbreak in the Democratic Republic of Congo. However, the reservoirs of ebolaviruses have remained enigmatic, though fruit bats have been implicated and demonstrated as the reservoir for related Marburg virus. Last year a sixth ebolavirus species, Bombali virus, was reported in saliva and feces from bats in Sierra Leone.
The new research focused on developing enhanced preparedness for emerging infectious disease threats, by researchers from University of Maasai Mara University, the University of Nairobi and the University of Helsinki, has now identified Bombali ebolavirus in an Angolan free-tailed bat (species: Mops condylurus) captured at Taita Hills, southeast Kenya. No ebolaviruses have been previously reported from wildlife in Kenya or other countries along the east coast of Africa. The researchers recovered high amounts of Bombali ebolavirus in bat tissues, including its full genome, confirming that productive infection does occur in this species. The bat was also shown to have antibodies towards the virus.
There is no current evidence that Bombali virus infects people. Evidence against apparent human infection was obtained by screening febrile patients reporting to clinics in the Taita Hills who have had contact with bats: no signs of Bombali virus infection or past exposure were uncovered. However, vigilance and ongoing monitoring are important to understand this viral infection and the risks it may pose to people, and further research is ongoing. Given the vast distance between the identification sites in Sierra Leone and Kenya (ca. 5500 km) and that the bat species involved are not believed to travel large distances, Bombali virus is likely to be transmitted across its range in much of sub-Saharan Africa. Although recently found, it is obvious that Bombali virus along with other ebolaviruses have been around since ancient times. The bat biologist expert of the team, Dr. Paul Webala from Maasai Mara University, emphasizes that despite being occasional virus carriers, bats are essential components of global ecosystems, serving critical functions such as insect pest control, seed dispersal and plant pollination, and their conservation is vitally important. Bats can indeed transmit deadly diseases like rabies and Nipah to humans, though transmission is exceedingly rare and easily avoided. In fact, having a virus in itself does not necessarily mean that they will automatically spill over to humans, endangering their health. Therefore, Dr. Webala avers that there is no justification whatsoever for their persecution as doing so will only harm bats and efforts to conserve them, and may compromise their roles in providing invaluable ecosystem services that benefit humans, wildlife and the environment. Previous eviction and culling attempts in response to possible disease outbreaks have backfired and may actually expose humans to potential risks of transmission.
The bat samples were collected at the University of Helsinki Taita Research Station and processed in Biosafety Level-3 laboratories of the Veterinary Faculty at the University of Helsinki. Positive samples were transferred to a Biosafety Level-4 facility in Stockholm for further investigation. The findings have been published in the Centers for Disease Control and Prevention journal Emerging Infectious Diseases.