McGill University. CAN: In April,
shortly after the World Health Organization announced that the Zaire
Ebolavirus was responsible for a number of deaths in southern Guinea, an
international team began the search for the animal origins of the
epidemic. The team wanted to know whether there was a larger Ebolavirus
outbreak happening in wildlife in the region and how the index case, a
two-year-old boy in Meliandou, Guinea might have gotten infected and
sparked the epidemic that has since spread into other areas of Guinea
and then Sierra Leone, Liberia, Nigeria, Senegal, the U.S, Spain and
Mali, representing the largest ever recorded outbreak.
What did the wildlife samples show?
Fortunately for the animals in the forest -- and mirroring the
findings of the monitoring team led by Vincent Lapeyre in Guinea --
these wildlife samples all tested negative for the virus. In Guinea, the
estimates of large mammal densities before and after the outbreak
further suggest that there has been no major decline in this region and
that there was likely not an “amplifying epidemic” in wildlife in the
region.
What led the team to deduce that the epidemic may have stemmed from contact with bats?
Since the monitoring data showed that larger wildlife in the region
didn’t experience a recent decline, they seemed unlikely to have served
as the source for the Ebola virus disease epidemic. But fruit bat
hunting and butchering are common activities in southern Guinea and
children are also exposed to insectivorous bats through hunting in and
around villages. The bat-surveying team found no fruit bat colonies in
the index village in Guinea, but discovered a large burnt tree near the
home of the two-year old boy who was the first reported case. Children
reported playing in and around this tree, which had burned accidentally
on March 24th, shortly before the research team arrived. Luckily the
team was able to identify the species of bats that had inhabited this
tree by deep-sequencing soil and ash samples. This bat species, Mops condylurus,
has been implicated in a previous ebolavirus outbreak, can survive
experimental infections, and has even shown hints of antibodies against
ebolaviruses in the wild, so they seem the most likely source of the
present epidemic.