Ebola has been the number one health buzzword throughout 2014. As this year draws to a close, are we any closer to gaining insight into the origin of this devastating, deadly virus? Researchers from the Robert Koch Institute in Berlin, Germany, may have finally located the source: free-tailed bats.
As of December 24th, Ebola outbreak case counts have skyrocketed to numbers totaling 19,497 cases, 12,418 laboratory-confirmed cases and 7,588 deaths. The US has experienced four of these cases, with one death.
Experimental vaccines and treatments for Ebola are under development, but where did Ebola virus come from and how did it transmit to humans?
Ebola virus disease is of zoonotic origin, meaning a disease that has been transmitted to human populations from animals, through two possible infection routes:
- Contact with larger wildlife, or
- Direct contact with the infected animal itself.
The second infection route appears more plausible, as direct contact with bats is usual in the affected region.
The animal – in which a zoonosis lives its existence, over the long term, and without causing symptoms – is called a reservoir host.
The study, published in EMBO Molecular Medicine, suggests the outbreak of the Ebola virus disease occurring in West Africa may have originated from contact between humans and virus-infected bats. The insectivorous free-tailed bats in particular have been identified as plausible reservoir hosts.
It was previously thought that fruit bats of the Pteropodidae family, attracted by towering reeds and oil palm cultivations in the remote area, are the natural hosts of Ebola virus and passed the virus to humans. However, in the village of Meliandou, located in Guinea’s Gueckedou province, the locals reveal an alternative source.
Meliandou was home to Ebola’s first victim, Emile Ouamouno, who was just 2 years old. The virus subsequently took the lives of his 3-year-old sister and their pregnant mother in the days that followed.
Interviews with Meliandou locals revealed that exposure to fruit bats through hunting and consumption of meat in this region is common, yet fruit bats seem an unlikely source of infection.
The authors note that if the infection had occurred as a foodborne transmission, the adults would have been infected before or concurrently with the 2-year-old boy. But this was not the case, which suggests the source of infection is unrelated to food.
A second opportunity for infection could be attributed to a large colony of free-tailed insectivorous bats, housed in a hollow tree nearby the home of Emile. Villagers report that children often used to play in and around the tree – this may have resulted in a massive exposure to the bats.
In April 2014, the multidiscipline teams of researchers led a 4-week field mission in Guinea to examine human exposure to bats, to survey local wildlife and to capture and sample bats in Meliandou and neighboring forests.
The results of the research reveal free-tailed bats as a likely source of the Ebola epidemic in West Africa and that larger wildlife populations are not the source of infection.
Study leader Fabian H. Leendertz, of the Robert Koch Institute, says:
“We monitored the large mammal populations close to Meliandou in south-eastern Guinea and found no evidence for a concurrent outbreak.”
These new findings begin to shed light on the source of the deadly virus that spread from Meliandou into other areas of Guinea and Sierra Leone, Liberia, Nigeria and Senegal.
Medical News Today recently reported findings from a study that reveal the success of an Ebola vaccine in an African population.