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Ebola mystery may be solved

HELEN BRANSWELL
Wednesday, November 30, 2005
Canadian Press

A team of scientists may have cracked the mystery of the reservoir or source of the deadly Ebola virus, finding evidence of the virus in three species of fruit bats in Gabon and the Republic of Congo.

While they say their work isn't proof positive that these bats are the sole reservoir of Ebola, they believe their findings "strongly suggest" these bats are one source of the virus.

"We can not exclude that other species of bats might also be a reservoir," lead author Eric Leroy said in an e-mail Wednesday from Gabon, where he is based at the Centre International de Recherches M?dicales de Franceville.

Fruit bats are eaten by humans in the areas where Dr. Leroy's team studied, suggesting a possible mode of transmission of the virus. The paper says educating people about the risk of eating bats may help reduce future outbreaks in humans.

Dr. Karl Johnson, co-discoverer of the virus, said he never thought it would take 30 years to find the source of Ebola when he flew to Northwestern Zaire in 1976 to investigate a mystery virus that had wiped out an entire hospital.

It was the first reported outbreak of what Dr. Johnson, who was then with the U.S. Centers for Disease Control in Atlanta, named Ebola virus after the river that flowed near the hospital.

While stressing these finding aren't a slam-dunk, Dr. Johnson nonetheless called the work the closest yet to defining the natural host of the Ebola virus, which randomly jumps into populations of great apes or humans with devastating consequences.

"It's the hottest thing ever in terms of pointing a direction," he said in an interview. "I think it's definitely worth major league follow up."

The team, from institutes in Gabon, Paris, Sandringham, South Africa and Thailand, reported their work in this week's issue of the journal Nature.

Following outbreaks of Ebola in humans and in apes in Gabon and the Republic of Congo between 2001 and 2003, the researchers set out to try to find the source of the virus.

They trapped 1,030 animal - including 679 bats, 222 birds and 129 small vertebrates - looking for evidence of Ebola.

Other teams, including one led by veteran U.S. virologist Dr. C.J. Peters, have done similar work over the years, but have failed to find any trace of the virus.

This team found antibodies to the Ebola virus in blood drawn from three species of bats. As well, fragments of virus were found in some of the bats using PCR or polymerase chain reaction testing.

That combination is considered strong evidence. But the ultimate proof eluded the group.

"The definitive conclusion is the isolation of the virus. We did not get it," Dr. Leroy said.

Dr. Peters, co-author and subject of the bestseller Virus Hunter and now director of the Center for Biodefense and Emerging Infectious Diseases at the University of Texas Medical Branch in Galveston, found the work persuasive.

"In the part of my brain that says 'These are things that I wonder about and these are things I believe,' I now believe that fruit-eating bats have been found to be infected with Ebola virus," he said in an interview.

"And I believe if I were going out there to look for the reservoir . . . I know where I would go. I'd go to where the fruit-eating bats live and I would follow them around and find out what they do."

Dr. Peters said more work needs to be done to determine whether these bats are getting the virus from something or somewhere else. He quickly added Dr. Leroy's team is probably already doing that work.

"I'll bet you that right now, they're . . . out there wherever these bats roost finding out what else is in that roost and catching it and studying it."

Dr. Johnson said as well that it is time to try to do experimental work in laboratories with these species of bats to test out the theory.

Dr. Peters said these findings should provide strong leads for the pursuit of the source of virus responsible for Marburg fever, another of the hemorrhagic fevers. Marburg, like Ebola, is caused by a filovirus.

"Certainly you'd go looking for Marburg in bats," he said.

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