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Hunting Down Ebola's Origins: Too Little Too Late?

Aug 20, 2014 06:46 PM EDT
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The deadly Ebola virus that is sweeping across west Africa, infecting and killing thousands of people, is thought have had originated in small and unassuming animals. Researchers have stumbled upon a number of carriers of the disease in the animal kingdom, where it is just as much an epidemic as it is in urban Africa. Some hope that finding the source of the disease will help them understand how it suddenly became so prevalent among humans.
(Photo : REUTERS)

The deadly Ebola virus that is sweeping across west Africa, infecting and killing thousands of people, is thought have had originated in small and unassuming animals. Researchers have stumbled upon a number of carriers of the disease in the animal kingdom, where it is just as much an epidemic as it is in urban Africa. Some hope that finding the source of the disease will help them understand how it suddenly became so prevalent among humans.

According to the World Health Organization (WHO), as of Aug. 18, 1,350 people have died from Ebola virus disease (EVD) - formerly known as Ebola hemorrhagic fever - with more than 1,100 additional cases of infection confirmed and currently receiving treatment. Even with early medical care from aid groups based in Guinea, Liberia and Sierra Leone, the WHO expects that about 90 percent of those affected will not survive the disease.

Nature World News recently reported about the new "miracle cure" that recently saved the lives of one American missionary and one doctor who were working in Liberia; however, that treatment is still considered "highly experimental" and was only administered to the Americans on compassionate grounds by the drug's manufacturers. The unfortunate truth is that there is no cure coming to west Africa anytime soon.

And experts know it.

Eating Some Bad Bat

That's why researchers are scrambling to confirm the biological origin of the outbreak, which was first identified in remote villages in the rainforest of eastern Guinea.

As of last March, Guinea officials had banned the sale and consumption of bat meat, according to BBC News. Rene Lamah, of Guinea's health ministry, hastily announced the ban while taking a tour of the forested region - the suspected epicenter of the epidemic.

You might be thinking, "Well of course eating bat would make you sick! That's why you don't eat bat!" But in fact, a lot of people do eat bat, and not only in remote villages in the rainforests of Guinea. (Scroll to read on...)

Paniki (Fruit Bat) meat cooked in spicy Rica green chilli pepper. An exotic Indonesian dish.
(Photo : Wiki CC0 - Gunawan Kartapranata) Paniki (Fruit Bat) meat cooked in spicy Rica green chilli pepper. An exotic Indonesian dish.

Travelers in parts of China, Thailand, Guam and even Australia might run across bats in food markets and restaurants. Varieties of fruit bats, including the sizable flying fox bat, are the most popular to eat. They are meaty and often beheaded, then deep fried with pepper and onions and sold as street food in more urban settings. For the most part, bat is just as healthy as any other bush meat.

Of course, the animal's diet certainly influences how safe it is. About 10 years ago, researchers found that flying fox dishes in Guam were actually slowly poisoning Chamorro people with a neurotoxin the foraging bats got from cycad seeds. However, the fruit-heavy diet of Guinea's bat population doesn't include this harmful seed.

Still, the bat ban was certainly not the wrong idea. Fruit bats of the Pteropodidae family have always been considered to be the natural host of the Ebola virus, and the first suspected victims commonly handled and prepared bat corpses for their village.

However, the actual transmission of bat-borne Ebola to humans was never confirmed.

A Wild Goose (Bat?) Chase

A study published in the journal Viruses last April found that Ebola has long been circulating among a great number of fruit bat species that find their homes across Asia, west Africa, Central Africa and the Congo.

However, similar to a study conducted on MERS-carrying Camels in Saudi Arabia, it simply left the question, "why now?" What exactly was so special about last December (when Guinea's first cases were identified) that sparked a massive outbreak in a portion of the world that has always seen just small and contained cases? (Scroll to read on...)

(Photo : U.S. Air Force - Staff Sgt. Melissa B. White)

Disease ecologist Kevin Olival, the author of the study, admitted that even with the virus pumping through their blood, "the evidence is scant that bats are to blame for the West African outbreak."

In the wake of this study's publication, Fabian Leendertz, an epidemiologist and disease ecologist at the Robert Koch Institute in Berlin, led a 17-member team to Guinea. He hoped to conclusively identify a strong animal-to-human transferrable - a process called zoonosis - strain of the virus the in the local fauna.

The study's results remain unpublished, but the researcher did reveal to Science News that they didn't find anything compelling.

"We were still three months late," Leendertz added. "Many things may have changed in the meantime."

It may simply be that disease carriers had already moved away from the area, with migration and unrelated environmental changes causing the outbreak's true culprits to wander away before the research team showed up.

"We didn't stumble across any dead animals," he lamented.

The Clue is in the Corpses

That sounds like a pretty morbid thing to be upset about, but the researcher has good reason to be disappointed.

A study conducted in 2012 found that a focused analysis of recently deceased animal populations in Ebola-affected regions were far more successful at identifying the responsible virus strain, compared to a study of live samples. (Scroll to read on...)

(Photo : Flickr: Miran Rijavec (Artist in doing nothing))

"You can't test every single animal, so we used information from historical outbreaks to figure out how to help the field response team focus their effort," Sarah Olson, a Wildlife Conservation Society (WCS) epidemiologist and the lead author of the report, explained in a statement. "It turns out that carcass sampling yields a 50 percent chance of finding Ebola virus or antibodies compared to less than six percent when sampling free-ranging live animals."

The study occurred in the wake of the predictable and contained Ebola outbreaks that occur in rural parts of Central Africa.

"This study digests over 30 years of accumulated knowledge so field teams can arrive informed and prepared," added senior author Damien Joly.

Interestingly, the study reports that only three percent of sample bat populations were carrying implicated Ebola strains. It was actually the carcasses of gorillas and chimpanzees that proved to be the most useful samples.

Too Little To Late

Unfortunately, a study published just this month in the Journal of Animal Ecology supports the theory that Leendertz and other investigators did indeed miss their opportunity to find the Ebola zoonosis source.

If gorillas are the prime samples, the affected population was likely long gone three months into the outbreak. (Scroll to read on...)

(Photo : pixabay)

According to Pascaline Le Gouar, senior author of the study, Ebola disrupts gorillas in a very unique way, with entire populations quickly moving from an affected region and dissolving.

"Along with the decrease in survival and in reproduction, Ebola outbreak perturbed social dynamics in gorilla populations," Le Gouar explained in a release.

According to the study, once gorillas became aware of an Ebola threat they began to purposely isolate themselves, no longer immigrating with neighboring populations and only rarely breeding. The result? The virus quickly runs out of hosts, disappearing from shrinking populations entirely in the course of a few months. 

And while that's good for gorillas, it leaves investigators with nothing to work with, and back at square one.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

- follow Brian on Twitter @BS_ButNoBS

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