A Deadly Ebola Mystery
Pastor Dale Morgan
Friday Apr. 27, 2007
*A Deadly Ebola Mystery*
By MICHAEL D. LEMONICK
Time Magazine
There's nothing like an outbreak of Ebola virus to guarantee screaming
headlines. That's largely due to the mid-1990s bestseller The Hot Zone,
which described the disease's horrifying course in gruesome detail,
leaving many readers to believe that Ebola posed a looming threat to
human existence. The truth is, however, that since the first recorded
human cases in the 1970s, only a few hundred people have died from it.
Of all the diseases you need to be afraid of, Ebola is near the bottom
of the list.
Unless, that is, you're a gorilla. Over the past decade or so, tens of
thousands of the great apes have died of Ebola in central Africa, along
with similar numbers of chimpanzees. That the disease was responsible
was established in a paper published in December in Science. Now a
report in the American Naturalist explains just why Ebola is spreading
among the animals so furiously — and shows how it could be stopped,
according to lead author Peter Walsh of the Max Planck Institute for
Evolutionary Biology in Leipzig, Germany. The epidemiological tactics
used to treat outbreaks of human scourges like E. coli hold the answer.
Ebola is transmitted by contact with body fluids, and it's rapidly
fatal. When people get it, they become so sick so fast — their organs
literally liquefy — that others try to stay away from them. What's more,
the mere fact of their quick immobility means they can't carry the virus
very far. Ebola usually burns through an isolated village or community
and then has nowhere else to go.
"People always assumed it was the same for gorillas," says Walsh. This
belief made particular sense since gorillas live in relatively compact
packs that don't interact much with other packs. Ebola, however, is
oddly aggressive in great apes, ignoring pack boundaries and advancing
across great-ape habitats at a rate of about 47 km a year. Heading into
the field to study the outbreaks, as well as animal behavior that could
be contributing to them, Walsh and his team soon cracked the mystery.
It turns out that animal epidemiologists had based all their Ebola
assumptions on mountain gorillas — the kind studied by Dian Fossey — and
not on Western gorillas, which were actually dying. The mountain variety
subsists mostly on leaves, which are available all over the forest.
Western gorillas, by contrast, live mostly on fruit, a scarcer resource
that draws different groups of gorillas and chimpanzees to the same
trees at different times of day. "They defecate and urinate in and
around the trees," says Walsh, leaving infected body fluids to sicken
the next group. Gorillas also examine the bodies of dead apes they come
upon, perhaps because they're smart enough to want to know if whatever
claimed that life is a threat to them. This provides another means of
direct transmission.
Now that the mechanics of the epidemic are known, putting the brakes on
it could be comparatively easy. Ebola vaccines exist, but public-service
announcements won't exactly bring gorillas to a vaccination center where
the entire population can be inoculated. Instead, epidemiologists can
use selective-vaccination techniques, which work with human communities
when universal vaccination isn't practical. Just inoculate a few gorilla
groups along the infection chain, and when the virus reaches them, it is
stopped cold.
"We're not talking about massive vaccination anymore," says Walsh.
"We're talking about getting a vaccine into key gorilla populations."
And the cost? Perhaps as little as $2 million — chump change, Walsh
calls it, to save our closest evolutionary kin from extinction.