Tuesday, August 12, 2014

How do bats both resist and transmit Ebola?

Ebola virus is the latest killer pathogen to make international news, and scientists are striving not only to keep people alive and prevent new cases, but also to better understand how the disease spreads and where it came from.

Ebola had not been seen in West Africa before the current outbreak. The strain now causing such tragedy in Guinea (where it started – here's a map), Nigeria, Sierra Leone, and Liberia is originally from Central Africa.

Scientists know the disease spreads through bodily fluids -- blood, tissue, saliva, urine, semen, feces -- and they have strong evidence that it doesn't spread through the air (mercifully).

So how did it cross all the way into West Africa?  There are 2 theories:  Bats and Bushmeat.

First the bats: Why do they seem to be in the center of so many horrific diseases, like Ebola, SARS, and Rabies?  They stay close to each other and have great resistance. Take a look at the video, it's just 3 minutes!

(Another great video from MinuteEarth!)

Second, the bushmeat, especially meat of apes or monkeys.

Ebola, like the other nasty viruses in that video, is relatively new in humans. People are contracting these diseases as they and their livestock get closer to wild animals that harbor the disease-causing pathogens. Good question – why are people getting so close to infected animals?

1) people like to eat bushmeat -- antelope, monkeys, pigs, birds, bats...
2) they don't know if an animal is infected, so they go ahead and kill it, handle it, and eat it
3) human populations keep growing and moving into forest areas, clearing it as they go and disrupting animal populations and normal behavior.

When animals lose their natural homes and sources of food and water, either they die or they start looking for new ones. Remember natural selection?  The species that can adapt to hardship and new conditions are the ones that are still with us today.

daily life for some South Asian villagers
photo: Elephant Action League

Those deer, pigs, or elephants that feed on crops and gardens, the jaguar or puma that eats a sheep, and the bats or birds that roost or nest under a roof instead of in a tree cavity are usually responding to a loss of their regular food and shelter. Left to fend for themselves in new, human-designed landscapes, they do their best to either move on or to survive, which brings them into close quarters with people.

And, typically, human-wildlife interactions include competition for food or space, and they often end badly, especially for the animals but often for people too. Ebola transfer hurts people more than bats, but then when people go on a kill-all-the-bats campaign, as they probably will, the bats disappear together with their pollination and insect-eating services.

Learn more about each of these (if you're curious and feeling serious):

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