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Bats responsible for recent West African Ebola epidemics

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For the first time, the type of deadly Ebola virus responsible for recent epidemics has been found in a bat in West Africa, The New York Times reports Liberian health officials have announced. Bats carrying the disease had already been found in Central Africa, and scientists have long suspected that bats were a natural host of Ebola and a source of some human infections in other areas as well. But until now they had not found any bats in West Africa that harboured the epidemic species, known as Zaire ebolavirus.

The report says although the bat was found in Liberia, the country has not had any human cases of Ebola since 2016, and the bat was not associated with any illness in people.

The finding is preliminary and not yet ready for publication in a peer-reviewed journal, the usual venue for presenting scientific discoveries, the report says. Only 20% of the bat’s genome has been studied, and research on it is continuing. But because of its potential impact on public health, officials in Liberia wanted to share the information widely as soon as possible.

“It’s an incomplete study, a work in progress,” said Simon J Anthony, a virologist at Columbia University who has performed genetic analyses on samples from the infected bat. “It feels premature scientifically, but on the other hand, you have the public health aspect. We do have enough data to suggest to me that it is Ebola Zaire in this bat. We agree with our Liberian government partners that this information should be shared.”

The report says knowing which types of bat carry Ebola may help health officials prevent outbreaks by educating the public about how to prevent contact with the creatures, scientists said. The newly implicated bat roosts in caves and mines, so people can be warned to avoid those places. But Anthony said there were probably more bat species, with different habitats, that might also carry the virus.

The report says avoiding caves is clear-cut advice, but other routes of infection may be harder to block: People in many parts of the world eat bats, and may be infected while catching or preparing them for cooking. Hunters and cooks may not be able to tell one bat species from another.

The researchers said the findings did not mean that bats should be exterminated. They protect humans and crops by eating insects and pollinating fruit trees. Disrupting complex ecosystems by slaughtering bats could even make disease outbreaks worse.

The report says Zaire Ebola virus is the cause of the current epidemic in the Democratic Republic of Congo, with more than 700 cases and more than 400 deaths. The outbreak, which has spun out of control in a war-torn region, is the second largest ever. The largest, caused by the same Ebola species, occurred in West Africa from 2013 to 2016, infecting nearly 30,000 people and killing 11,000.

The West African epidemic, in Guinea, Liberia and Sierra Leone, is thought to have begun with a small boy in Guinea handling an infected bat, but, the report says, the origin is not known for sure.

A Liberian team in full protective gear – Tyvek suits, gloves, masks, goggles, hoods, boots – trapped and released 5,000 bats from about 10 species. They took samples of blood, urine and faeces, and oral swabs.

The report says Anthony’s lab at Columbia found genetic material from the virus in a mouth swab taken from just one bat, captured in Liberia’s north-eastern Nimba District. That animal was a greater long-fingered bat, from the species Miniopterus inflatus, a furry beast the size of a small mouse, weighing half an ounce, with a 12-inch wingspan. It eats insects.

Tests also found that the bat had antibodies to the Zaire ebolavirus, an immune system response, providing further evidence that it had been infected.

The report says the research team came from the Liberian government, Columbia University, the University of California-Davis and EcoHealth Alliance, a non-profit group that studies emerging diseases that originate in animals and spill over into humans. The research was paid for by the US Agency for International Development and is part of a project called Predict, which is trying to find viruses before they jump into humans and cause epidemics.

The report says the bat did not appear sick from the virus, and scientists do not know how the animals become infected. The bats and Ebola have probably been associated for a long time and most likely evolved together, said Jonathan Epstein, a veterinarian and EcoHealth Alliance’s vice president for science and outreach.

 

The DRC’s Ebola outbreak has spread southwards into an area with high security risks, the World Health Organisation (WHO) said. According to a Polity report the outbreak, the country’s worst, has killed 439 of the 713 people believed to have caught the disease.

The fight against Ebola depends on tracing people who may have had contact with the disease and could fall ill and spread it further. But, the report says, the outbreak in a region of Congo with frequent fighting makes it hard for health workers to move around and monitor potential sufferers and to spread messages about how to avoid becoming sick.

Most of the cases since the start of the year have been in Katwa health zone, where the WHO said Ebola workers had faced “pockets of community mistrust” and most people falling ill were not on lists of people suspected of coming into contact with Ebola.

“The outbreak has also extended southwards to Kayina health zone, a high security risk area,” the WHO is quoted in the report as saying. There have been five cases in Kayina, which lies between the main outbreak zone and the major city of Goma, which is close to the Rwandan border.

The WHO said that after running an Ebola simulation exercise in Rwanda, it was sending a team to beef up the country’s preparedness and to vaccinate health workers who would be first to come into contact with Ebola if it spread across the border. However, WHO spokesperson Fadela Chaib said there had also been a decline in cases around the previous hotspot Beni.

“It is very premature to shout victory, it’s true we had some success in Beni because all the steps we’ve taken have had an impact, but unfortunately we see cases turning up in other areas,” she said. “The country is not only facing Ebola but other health threats, just to name malaria, cholera, vaccine-derived polio, and also a very long humanitarian crisis and a lot of violence in several regions.”

The report says more than 60,000 people have been vaccinated in Congo, as well as 2,500 in Uganda, one of the countries at “very high” risk from the disease. Chaib said there were 4,000 people with potential Ebola contact under surveillance and 156 patients in hospital.

The New York Times report
Polity report


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