Ebola-origin bats in the hollow tree?

Ebola epidemic probably started from bats in a hollow tree

31.12.2014

The current Ebola epidemic in West Africa probably originated in a hollow tree that served as a shelter for bats. Investigations conducted by the Robert Koch Institute (RKI) revealed that the so-called „Index patients“ (first infected patient) - a two-year-old boy from the village of Meliandou in Guinea - could have become infected while playing in the hollow tree trunk. The results of their investigations, the researchers have in the journal „EMBO Molecular Medicine“ released.

Already in former Ebola outbreaks, the bat species Pug condylurus was determined as an animal source of infection. Proof of the genetic material of these bats in a hollow tree trunk that served to play in the village's children therefore suggests that the biennial index patient may have become infected in this way. From the small village in Guinea, the disease then made its way into the cities, the neighboring countries of Liberia, Sierra Leone, other African countries, and occasionally to Europe and the United States. To date, according to the World Health Organization (WHO), nearly 20,000 people have become infected in the current epidemic and more than 7,500 people have died as a result of the infection.

Search for the animal source of infection
Shortly after the WHO confirmed that the Ebola virus was responsible for a number of deaths in southeastern Guinea, an international research team led by Fabian Leendertz, head of the project group, began „Epidemiology of highly pathogenic agents“ at the RKI, the search for the animal source of infection. The scientists traveled to the village of the two-year-old boy, who is considered an index patient of the epidemic, and went there, for example, the question of whether a major Ebola outbreak in the wildlife of the region occurs. For earlier outbreaks, significant thinning of stocks was also detectable in the animal world. This was not true here. And around the village there are, according to the RKI „no tropical jungle as in the places in Central Africa, where earlier Ebola outbreaks had started.“ As a result, the possible sources of infection were clearly limited.

Genes of bats detected
The researchers also interviewed the villagers (including the children) about their hunting practices, the contact with bushmeat and other local peculiarities. The scientists discovered a hollow tree near the local wash area. Here the children had played regularly until this - shortly before the arrival of the researchers - burned down. The tree was only 50 meters away from the house of the index patient. In the ash and soil samples, the researchers were able to detect DNA of the bat species pug condylurus, „which has been discussed as a potential reservoir in earlier Ebola outbreaks and is known to survive Ebola virus infections and have been found in antibodies to Ebola viruses“, so the message of the RKI.

Not bats, but bats
This suggests the suspicion that the animal source of infection of the current epidemic - contrary to previous assumptions - were not bats, but bats of the species pug condylurus. The current work offers the best possible insight into the origins of the epidemic. Although the bats could not be determined one hundred percent as the origin of the outbreak, as no animals of this species were found after the fire of the tree. But at least other locally caught bats and fruit bats showed no Ebola virus infection. „Further in-depth environmental and experimental studies are urgently needed to understand the role of these and other bat species in Ebola virus transmission as well as the distribution of these viruses in nature“, so the conclusion of the scientists. It also believes that the public should be better informed about the potential health risks of bats and be encouraged to minimize contact with the animals. Last but not least, warn of a stigmatization of the village of Meliandou, which was just unfortunate when the epidemic began here. (Fp)