Tree of life and death teaches about Ebola spread
PARIS // The world’s largest Ebola epidemic may have started inside a hollow tree in a remote village in Guinea.
The outbreak began with the death of a two-year-old boy in the village of Meliandou in December 2013.
Now the finger of suspicion has been pointed at free-tailed bats, Mops condylurus, that lived in the hollow tree only 50 metres from the boy’s home,
“The close proximity of a large colony of free-tailed bats … provided opportunity for infection. Children regularly caught and played with bats in this tree,” scientists from the Robert Koch Institute in Berlin concluded after an investigation into the outbreak, which has killed at least 7,800 people in west Africa in the past year.
The Ebola virus thrives in a natural haven, called a reservoir, among wild animals which are not affected by it.
The virus can infect humans who come into contact with this source directly, or indirectly through contact with animals that have fallen sick from it.
Highly contagious, the virus is then passed among humans through contact with body fluids.
One known reservoir is the fruit bat, or Epomophorus wahlbergi, a widespread tropical African species that in some countries is killed for food, offering an infection pathway to hunters and butchers.
The role of fruit bats in the current outbreak has never been confirmed. In contrast, free-tailed bats, a related species, have been found in lab tests to be able to carry the virus but not fall sick with it.
The German team said evidence that this species started the epidemic was not 100 per cent, but it was strong.
Local children not only played with the bats at the tree, they also hunted bats that roosted at village homes and grilled them for food.
The scientists also found no evidence of deaths among larger mammals, which would have been a secondary route of infection for humans.
On the other hand, no trace of Ebola virus was found in any of the bats the scientists captured and whose blood was analysed.
When the researchers came to Meliandou, they found the bat colony had fled, because most of the tree had burnt and only the stump and branches remained.
Traces of DNA in surrounding ash and soil pointed to the previous presence of the bats. But again, there was no presence of Ebola.
“The virus must be very rare in the reservoir,” said Fabian Leendertz, the scientist who led the investigation.
“That is also obvious when you think about how many tonnes of bat meat is consumed every year.
“If more bats carried the virus, we would see outbreaks all the time. That’s one of the challenges: the virus is rare and in a large multispecies reservoir.”
The possibility that this species of bat could be an Ebola vector is a worry, Mr Leendertz said.
Very little is known about how these bats live – when they migrate and reproduce, where and why they cluster, their sources of food – and only understanding this will quantify the risk for humans.
Africa’s population explosion has destroyed more and more of the bats’ habitat and brought more people into proximity with them.
Mr Leendertz said an early priority should be to encourage co-existence between villagers and bats.
Culling the insect-eating animals could encourage the spread of insect-borne disease.
“It is no solution to start killing bats or disrupting their habitat. That may backfire very badly,” he warned.
Published: December 30, 2014 04:00 AM