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Another Bat Die-Off Leads to Discovery of First European Ebola Virus Relative

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Marburg Virus. Note distinctive "Shepherd's crooks". CDC/ Dr. Erskine Palmer, Russell Regnery, Ph.D., CDC Public Health Image Library #275; Public Domain. Click for link.

Back in 1994, Richard Preston scared the bejeesus out of everyone with his eye-opening non-fiction thriller “The Hot Zone”. It was a gripping read, and teenage me couldn’t put it down. In it, Preston documented the depredations of filoviruses — a family of wildly contagious filamentous RNA viruses that cause horrible, gory, swift deaths by multiple organ failure. You may be bleeding from any number of orifices when this happens.

Death rates for the two classic filoviruses — Marburg Virus and Ebola Virus — hover between 30 and 90%, and for Ebola, consistently hit the higher end of that range. In fact, death is so swift that experts have theorized that it actually limits the success of the virus among humans. It so far has failed to escape either Africa or the labs in which it is studied in other continents. So far.

One of the central mysteries of “The Hot Zone” was just where the viruses were coming from. Although it was clear that some apes and primates could also get sick, they, too, died from it. They did not seem to be hosting the virus during quiet periods in which the disease disappeared. Based on studies of victims who hadn’t gotten sick by eating contaminated bushmeat, suspicion fell on caves, and perhaps bats, but nothing conclusive could be shown.

In the last two decades, evidence has accumulated that bats are, indeed, filovirus’s true hosts. I covered one such revelation in a blog post here. Up ’til now, it has seemed as if bats infected with Marburg or Ebola were perfectly healthy, however, and only when the viruses escaped into primates did they become lethal. It now appears that that isn’t always the case.

It flew under the radar last fall, but in October scientists announced the discovery of the first filovirus found not in Africa or Asia, but in Europe. It’s not time to hit the panic button yet, though. In the case of the new virus, it seems like it’s the bats we should be worried about.

The slinky, sinuous, and frighteningly efficient killer Ebola Virus. Note the branches in this filament. CDC/ Cynthia Goldsmith. CDC Public Health Image Library #1832. Public Domain. Click image for link.

Sometime in 2002, Schreiber’s bats (Miniopterus schreibersii) across France, Spain, and Portugal died by the score. In Spanish caves, several bat colonies were wiped out in less than 10 days. The dead bats looked normal, but their lungs were filled with immune cells while their spleens were depleted of them. The signs pointed to viral pneumonia.

A team of Spanish and American scientists, who reported their results to PLoS Pathogens last year, tested dead bats found in Lloviu Cave (that’s pronounced “Yo-view”, I think) in Spain for a variety of viruses, and found evidence of filovirus DNA in the expired bats. Healthy bats showed no sign of infection. Although the researchers took pains to note that they had not demonstrated causality, the evidence seems pretty damning for the virus in question, which they named Lloviu Virus.

When they sequenced up their virus, they found it to be a new type that displayed characteristic filovirus traits: a mere seven open reading frames (basically, genes) on a single strand of negative-sense RNA. Analysis of its RNA polymerase — the enzyme it uses to replicate its genome — indicated it is more closely related to Ebola virus than to Marburg virus, but that it’s clearly not nested within the Ebola viruses and is in a group of its own. (See Fig. 3 in the paper)

Though bats seem easy prey for this virus, so far there seem not to have been any human infections, in spite of human visitors to virus-infested caves. Perhaps that has something to do with the fact that the filoviruses that are pathogenic to humans seem to co-exist happily with bats, while Lloviu virus bumps off bats. Or perhaps not.

In any case, I think it is the bats we should be worried for.  Given the devastating losses we’ve seen in North America thanks to the fungus Geomyces destructans, the cause of White Nose Syndrome, it’s unsettling to hear about another emerging pathogen of bats. I can’t find any information on whether these die-offs have continued since 2002 or not, or whether they threaten European bats the way that White Nose looms here.

However, the authors of the study note with some concern that the geographic distribution of the affected bat M. schreibersii in various locations throughout the sub-tropical Old World (though interestingly totally outside filoviruses’ traditional African stomping grounds) and the tendency of known filoviruses to have a stable host-parasite relationships may mean that there are many more bats at risk. Though homely, bats help keep the world running smoothly. The last thing they need is another pestilent disease — especially one who comes from a virus family with such a nasty reputation.

I can’t find any information on whether these die-offs have continued since 2002 or not, or whether they threaten European bats the way that White-Nose Syndrome has devastated North American bats.
Jennifer Frazer About the Author: Jennifer Frazer is a AAAS Science Journalism Award-winning science writer. She has degrees in biology, plant pathology/mycology, and science writing, and has spent many happy hours studying life in situ. Follow on Twitter @JenniferFrazer.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. kdimoff 2:51 pm 04/3/2012

    crazy fascinating. i like bats. ebola, not so much. viruses are so interesting. side note, i had been surprised to see a bat as the start of the pandemic in the movie “contagion”. of course, it was totally fiction, but i had thought that birds->pigs->humans was the normal host-to-host-to-host transmission. bats plus filovirus puts a new spin on it, and another pr loss for bats :(

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  2. 2. Xenobio 9:25 am 04/14/2012

    KDimoff, the virus in Contagion was supposed to be a fictionalised version of Nipah virus, not Ebola. In the outbreak in Malaysia when it was first discovered, the transmission route was indeed bats -> pigs -> humans. In India and Bangladesh where there is little to no pig farming (due to being mostly Hindu and Muslim communities), the route is bats -> palm nectar/juice containers -> humans. Outbreaks occur pretty frequently in India & Bangladesh whereas there has been no outbreak in Malaysia since the first one. There has been some success in preventing Nipah by getting people to cover the juice containers that are left in the palm trees overnight, so that the bats can’t get into them.

    Nipah is also closely related to Hendra virus in Australia where it goes bats -> horses -> humans.

    The bats that are getting killed off by WNS in North America and the Spanish bats in this article are insect-eating bats (microchiroptera, or kelawar in Malay). The bats that spread henipaviruses are fruitbats (megachiroptera, or keluang in Malay). Fruitbats mostly do not live in caves if I remember correctly.

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  3. 3. Xenobio 9:32 am 04/14/2012

    Btw, in case I wasn’t clear enough, Nipah is not (closely) related to Ebola. They are both in Mononegavirales but Nipah is a paramyxovirus, not a filovirus. Aside from the obvious parallels with the natural history of Nipah, you can kind of see this in the movie where the people at the CDC are doing a BLAST search or something and there’s some line in the results that says morbilivirus.

    Also, I thought the timeline in the movie is totally ludicrous. 21 days might be enough time to make a crude vaccine like formalin-inactivated mashed infected monkey brains, but certainly not long enough to test it, let along to make and test a live attenuated vaccine, ESPECIALLY from a previously unknown virus. Also, the professor who continued working on it after the government ordered everyone outside the CDC to stop work wouldn’t be a hero, he’d be in jail.

    Yes, I know it’s Hollywood…

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  4. 4. Contagions Round-up 22: Unusual Pathologies & Prevention Schemes « Contagions 12:09 am 04/21/2012

    [...] Frazer, the Artful Amoeba, posted on a newly discovered Ebola-like virus in European bats, on the trail of Kawasaki disease transmission and on the marine bacterial origins of [...]

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  5. 5. kdimoff 12:04 am 05/12/2012

    xenobio, oh totally, there were holes all over that movie! and i know it wasn’t ebola, i guess i thought it was more like an avian flu or “swine” flu so i just found it interesting that they had used bats. that’s the first time i had ever considered bats as an original host! and now i’m even more curious now that you mention the nuances between countries that do/do not farm pigs and the virus still find a way, like in the case of the palm nectar!

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