The filaments of the Marburg virus, which can be straight or contain a "shepherd's crook", and which gave the filovirus family its name.This photo of the Marburg virus brought to you by the number 11, the letter d, a backwards Egyptian s, and an important (and suggestive) year in US history with a bubble wand on top. Also, by the CDC and Drs. Erskine Palmer, Russell Regnery, and Hermann Rorschach, who in no way support or endorse my interpretation. Magnification 100,000 x.
As if the bats of the world didn’t already have enough to contend with, what with their bad (albeit sometimes deserved) rap for rabies and drinking human blood, numerical decline thanks to habitat loss, and the White Nose Syndrome that is anihilating the bats of eastern North America (and maybe eventually all of North America), last month came news that a reservoir for the deadly Marburg virus had been confirmed: African cave-dwelling fruit bats.
This is big news because scientists have been looking for the natural reservoir species for Marburg and its cousin Ebola for some time. Marburg and Ebola are hemorrhagic fever viruses that are among the deadliest on the planet*. They are sole members of the Filovirus family, and are single-stranded negative-sense RNA viruses. Mortality rates range between a quarter and nine-tenths of those infected. And Marburg is not a pleasant way to go. Here’s how the CDC describes it:
After an incubation period of 5-10 days, the onset of the disease is sudden and is marked by fever, chills, headache, and myalgia. Around the fifth day after the onset of symptoms, a maculopapular rash, most prominent on the trunk (chest, back, stomach), may occur. Nausea, vomiting, chest pain, a sore throat, abdominal pain, and diarrhea then may appear. Symptoms become increasingly severe and may include jaundice, inflammation of the pancreas, severe weight loss, delirium, shock, liver failure, and multi-organ dysfunction.
Sounds fun! Hemorrhagic fevers are so called because they somehow punch holes in capillary walls that allow blood to seep into the body and out of certain external openings you would not wish blood to ever pass through. As recounted in Richard Preston’s gruesome early 90’s bestseller The Hot Zone , this can cause people to spill or spatter infectious blood all over any unfortunate passersby or airline seatmates (sometimes the little “summon stewardess” button can’t fully convey the depth of your need). It must be said, however, that the bleeding isn’t usually what kills you, and that unlike its cousin Ebola, Marburg is not nearly so inclined to make you bleed from bodily orifices. Whew!
In The Hot Zone, Preston described (at least in my memory) how some cases of Marburg or Ebola were found in people who recently visited mines or caves or who had spent times in rooms or factories where bats roosted. Although some people seemed to acquire the virus from sick apes or bushmeat, scientists already suspected the virus reservoir, or full-time host, was not apes or monkeys, because they die just as we do from the virus. Suspiciously, however, apes and monkeys that transmitted the virus had often fed at fruit trees that bats frequented. But repeated tests of bats and the sticking of unfortunate “sentinel species” in caves to see if they got sick could never produce leads. For decades, scientists were baffled and frustrated. How could such a deadly virus remain so mysteriously hidden?
Then four years ago a survey of more than a thousand small vertebrates Gabon and Democratic Republic of Congo during an Ebola outbreak turned up evidence of asymptomatic Ebola infection in bats, hinting they might be the long-sought reservoir. Inspired, scientists in 2007 finally isolated antibodies and Marburg virus genetic fragments from fruit bats. Then last month an article in PLoS Pathogens contained the damning evidence: the isolation of live infectious viruses from the Egyptian fruit bat (Rousettus aegyptiacus) in Kitaka Cave, Uganda. There can be little doubt now that bats are carriers.
Could you resist this face? No! Bad bat! Don't give me deadly Marburg Hemorrhagic Fever! The Egyptian Fruit Bat, Rousettus aegpitiacus. Courtesy Dawson, Creative Commons Attribution 2.5 License.
The infected bats appeared healthy, and the genetic diversity of the viruses found in Kitaka Cave seems to indicate Marburg has been living with and adapting to the bats for a long time. If the virus had only recently penetrated the bat population from another species, you’d expect there to be only one or a few virus types.
Moreover, a significant share of the bats in the surveyed cave are infected. About 5.1% of their sample hosted the virus, which, if extrapolated, would mean over 5,000 bats out of an estimated 100,000 in the cave are infected. And indeed, two miners infected in Kitaka were sickened by different strains of the virus, implying they picked up their diseases independently and that human transmission is not a rare event. The strains, though different, closely matched the sorts of strains found in the scientists’ fruit bat samples.
Although the viral lineages were highly variable within Kitaka Cave, some strains found in one part of Africa were much more closely related to strains found in caves hundreds of miles away than they were to strains in their bat neighbors. As the bats migrate hundreds of miles and mingle over most of the continent annually, it’s not hard to see why Africa may be one giant Marburg virus melting pot.
I just hope this news doesn’t prompt a bat holocaust in Africa on the part of people, corporations, or authorities. Bats have enough troubles already and [cliche alert] provide valuable ecosystem services[/cliche alert] by hoovering up pesky insects and/or dispersing seeds. The solution, I think, is bat avoidance, though how practical that is in a mine I do not know.
Note to self: scratch caving in Africa off to-do list**.
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*In other news, the first-ever case of Marburg in the United States was recorded in February in Colorado . . . wait, what? A deadly Ebola relative made its way to Colorado this year and I didn’t even know it? How they managed to keep the fact that a virus with a 90% mortality rate was in Colorado on the DL I’ll never know, although I did find an article in the Rocky (RIP) about it ex post facto. I need to start keeping closer tabs on our local newsgathering establishment.
**Several of the people who got sick (including the Colorado victim) did so after visiting some sort of “python cave” in Uganda that also is home to thousands of bats (do the snakes just sit on the ground with their mouths open waiting for manna from heaven?). Second note to self: question sanity if *ever* consider visiting something called a “python cave”.
“Snakes. . . . why’d it have to be snakes?”
“Pythons. Very dangerous. You go first.”
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If I ever hear you talking about going to a “python cave”, I shall first get the worst attack of heeby-jeebies since the screening of “Killer Klowns from Outer Space”. Following that, I will surely summon the nice men in their clean white coats.