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Is a Cure or Vaccine for Ebola in the Blood of Bush Hunters and Ebola Survivors?

Planned Clinical Trials of Convalescent Serum Offer Hope -- but Face Many Hurdles and Concerns About the Impact on HIV and Hepatitis

November 26, 2014

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Global health journalist, activist and author Anne-christine d'Adesky

Global health journalist, activist and author Anne-christine d'Adesky

Most Americans might never step into, buy or eat something from a rural Chop Bar in West Africa, a typical feature of roadside markets that line dirt roads leading deep into the interior bush. There, one can encounter traders hawking buckets of dried out bats or the still-fresh, bloodied stumps of any number of exotic species -- hippo, gazelle, monkey, snake. Across Africa, bushmeat, as it's called, has long been a staple for locals, just as Americans eat hamburgers and chicken wings. In recent years, the export market for bushmeat has grown, turning up on the menus of fancy restaurants the world over. But now, with over 14,000 West Africans exposed to the fast-spreading Ebola virus and 5,200 dead from the disease (as of mid-November), there's a renewed interest in bushmeat as a possible source of contagion for humans, and a stronger consumer warning: Don't eat it.

In the early years of AIDS, similar concerns about tainted bushmeat were raised when SIV (simian immunodeficiency virus) strains were identified in primates. Tabloid stories, some with racist overtones about primitive African customs, warned against sex with monkeys and eating monkey meat. In fact, studies showed the greater risk of exposure was to bush hunters and traders handling bloody meat and carcasses who might have cuts on their hands that could increase a theoretical risk of exposure to a blood-borne animal virus. Cooking kills viruses, reducing the risk of exposure from eating cooked bushmeat.

To date, Ebola viruses have been isolated in many animals, and can live up to 20 days in a carcass. As with SIV, bushmeat hunters may be at higher risk of exposure. Could that be why some of them may also be immune to Ebola?


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Tales of Immunity Among Bushmeat Hunters

That's a tantalizing question raised by some rural hunters in Ebola hot zones who claim they -- and their families and communities -- are resistant to Ebola. University of California, Berkeley researcher Justin Brashares is an assistant professor of Wildlife Ecology and Conservation at the UC's Department of Environmental Science, Policy and Management, who studies animal diseases that can be passed to humans. He's also a bushmeat expert who's been reviewing migration patterns of fruit bats in West Africa and the link to Ebola. His early findings suggest that where the bats fly -- and poop -- Ebola will later turn up. Fruit bat droppings are eaten by other species, including monkeys, who are then hunted. Put crudely, bat shit offers a road map to track Ebola: where it's going and where it's been.

During his field work, Brashares has met bush hunters who never got sick from the virus and claim they're immune to Ebola. "We don't know how many people may have acquired resistance to Ebola, but it's something we need to look at now," said Brashares, speaking at a recent UC forum on social pathways to Ebola's spread. "It's possible it could be widespread but we don't have the research to back this up yet. We haven't looked at their blood."

So while health officials warn against bushmeat, could those who hunt and sell it be somehow more protected? Could exposure have seeded, or be newly seeding, immunity to Ebola in some rural communities? And could this immunity be genetically passed on? Such questions underlie new Ebola treatment and vaccine studies being rolled out in different countries. What's not in dispute is that locals have always hunted and eaten bushmeat in West Africa long before 1976, when Ebola was first documented in a human.


Acquired Immunity to Ebola Is Compelling, With Trial to Start in December

The immunity claims of rural hunters support a growing number of documented cases of West Africans, and now U.S. health care workers, who tested positive or got sick from Ebola Viral Disease (EVD) then recovered and appear immune to reinfection. This resistance -- an acquired immunity to the Ebola virus -- can be measured in titers of neutralizing antibodies to the virus in their blood. Antibodies are proteins generated in response to a viral invader; neutralizing antibodies recognize and kill or disable that invader.

In December, a first clinical trial in Guinea will test how well blood transfusions from recovered Ebola patients can treat or cure others exposed to the virus. There's a lot of hope this approach will work, based on early cases with albeit mixed results.

"It's a very compelling approach but there are many questions that it raises," Dan Bausch, a member of the WHO Filovirus Working Group and WHO advisor on EVD Convalescent Serum as a therapy, told TheBody.com. "We need to proceed quickly, but carefully."

For starters, the trials must establish the safety of convalescent serum. While blood transfusions have become routine in African clinics, the possible coinfection of patients with HIV or hepatitis worries AIDS activists. In a recent journal editorial, Nigerian ethics researcher Morenike Upkong warns about a theoretical risk of spreading HIV and hepatitis. She cited 2011 prevalence rates of hepatitis B (HBV) at 9.8% and HIV rates of 1.4% in Guinea as evidence backing her concerns. Today, Guinea has a very weak health system with one doctor per 71,000 residents.

"Ebola infected countries may therefore see an upsurge in the prevalence of other blood-borne infections both during and following the EVD epidemic, further taxing the health care system," she writes, advocating training for health providers on proper blood management and addressing public myths, stigma and misperceptions about Ebola to reduce these risks.

As noted by reporter Theo Smart in coverage of a roundtable discussion at the recent American Society of Tropical Medicine and Hygiene meeting in early November, reports are emerging of a black market in Ebola survivor's blood. He quotes Dr. Lina Moses of Tulane University, who has been working in Sierra Leone and Liberia during the current outbreak, who said:

I've first-hand seen requests for this from several survivors. But one of the problems with black market convalescent serum is that it has not been screened for other pathogens -- which makes it particularly dangerous. It is also something that a lot of organizations don't have the power to enforce. The ministries of health in these three countries really need to take a hold of this very serious issue.

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