Ongoing Ebola outbreak traced to hollow tree | Science News for Students

Ongoing Ebola outbreak traced to hollow tree

Resident bats may have infected a two-year-old boy, the outbreak’s first victim
Jan 23, 2015 — 1:00 pm EST
hollow tree

The first victim in the current Ebola outbreak had played in this hollow tree. It has since burned down. Scientists say the tree used to host insect-eating bats that could have carried the Ebola virus. 

FABIAN LEENDERTZ

More than 21,000 people have been stricken by the ongoing Ebola outbreak in West Africa. Of these, 8,400 have died. That epidemic may have started in a hollow tree, scientists now report.

Two-year-old Emile Ouamouno appears to have been the massive outbreak’s first victim. The boy, who died of Ebola in December 2013, lived in the remote village of Meliandou in Guinea. He and his friends often played in a hollow tree near his home. But that tree also was home to a species of insect-eating bat (Mops condylurus), scientists report in the January issue of EMBO Molecular Medicine. Previous studies had pointed to that species as a possible carrier of the Ebola virus.

These insect-eating bats often dwell near people. They may even roost in homes. Because of this close contact, Fabian Leendertz worries that the next Ebola outbreak can start anywhere that these bats live. Leendertz works at the Robert Koch Institute in Berlin, Germany. As an epidemiologist, he investigates where a new disease might have started and its source.

In seeking the roots of the new Ebola outbreak, Leendertz and his team traveled to Emile’s village four months after the boy had died. They wanted to find the source animal, or reservoir, of the virus to figure out how people had first come into contact with it. But when the researchers arrived, the hollow tree had already been burned. Its bats were gone.

So the scientists interviewed villagers and studied nearby wildlife.

Many people in Africa eat bush meat — wild animals such as bats, monkeys, great apes and antelope. Fruit bats had been a prime suspect for triggering the Ebola outbreak. People come into contact with the virus by eating infected fruit bats or fruit that had been in contact with an infected bat. But the scientists determined that these bats likely were not to blame. No fruit bats roosted in Emile’s village.  The scientists also found no evidence that the boy or his family had eaten fruit bats.

In fact, they found no infected bats of any kind in or near Emile’s village. The researchers did learn, though, that insect-eating bats used to live in that hollow tree where the children had played. Such bats had been linked to earlier Ebola outbreaks. That makes them the most likely suspects in the recent outbreak, Leendertz and his colleagues concluded.

The case isn't closed. Leendertz says he cannot yet completely rule out fruit bats as the source of the virus’ spread into people. And Tony Schountz told Science News that the new evidence for these insect-eating bats “is largely circumstantial.” That means it points to a connection but falls short of being solid proof. Still, “it's a start for sure,” Schountz said. He's an immunologist at Colorado State University in Fort Collins and has studied viruses in bats.

Because people can be warned to avoid contact with certain animals, such as bats, Schountz told Science News that it's important to identify which species may carry dangerous diseases. “We have a good chance of modifying human behavior,” he said. “We have no chance of changing the bats.”

Power Words

bush meat   Wild mammals eaten by people, including not only cats, Chinese bamboo rats, squirrels, badgers and civets but also primates, such as monkeys, chimps and gorillas.

carrier    (in medicine) A person or organism that has become infected with an infectious disease agent, but displays no symptoms. The infamous “typhoid Mary” was a well-known example — an individual who could infect others with a killer disease but showed no signs of disease herself.

Ebola  A family of viruses that cause a deadly disease in people. Most cases occur in Africa and Asia. Its symptoms include headaches, fever, muscle pain and extensive bleeding. The infection spreads from person to person (or animal to some person) through contact with infected body fluids.

epidemic  A widespread outbreak of an infectious disease that sickens many people in a community at the same time.

epidemiologist  Like health detectives, these researchers figure out what causes a particular illness and how to limit its spread.

outbreak  The sudden emergence of disease in a population of people or animals.

reservoir A large store of something. People who study infections refer to the environment in which germs can survive safely (such as the bodies of birds or pigs) as living reservoirs.

virus  Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.

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Further Reading

T.H. Saey. “Insect-eating bats implicated as Ebola outbreak source.Science News. Dec. 31, 2014.

J. Raloff. “Ebola epidemic could top 1 million, CDC warns.” Science News for Students. September 24, 2014.

S. Ornes. “Ebola update: Signs of hope.” Science News for Students. Sept. 12, 2014.

J. Raloff. “Ebola emerges in the Congo.” Science News for Students. August 27, 2014.

J. Raloff. “What is Ebola?Science News for Students. August 22, 2014.

N. Seppa. “Ebola treatments and vaccines could be near.Science News for Students. August 22, 2014.

T.H. Saey. “Record Ebola epidemic strikes.” Science News for Students. August 8, 2014.

A.L. Mascarelli. “Explainer: Animals’ role in human disease.” Science News for Students. August 15, 2013.

A.L. Mascarelli. “Infectious animals.” Science News for Students. April 17, 2013.

J. Raloff. “Bush meat can be a viral feast.” Science News Online. Jan. 12, 2012.

Original journal source: A. M. Saéz et al. Investigating the zoonotic origin of the West African Ebola epidemic. EMBO Molecular Medicine. Vol. 1, January 2015, p. 17. doi: 10.15252/emmm.201404792