Bats, along with spiders and snakes, are one of the most frequently feared animals. Ask any bat lover, and they will tell you that these creatures are harmless and unfairly maligned. Sure they carry rabies, but so do many other animals, including "man's best friend" the dog. People's phobias, they maintain, comes from the medieval association of bats with the Devil, or from fear of the dark, or vampire legends, or some such thing. Bats are cute and good for the ecosystem. Leave them alone and they'll leave you alone.

That last sentence may be true, but apparently some bats aren't harmless. Certain bats are now suspected of causing some of the world's most feared diseases. And all the trouble started because some people, rather than leave them alone, eat them.

Australian researchers Lin-Fa Wang and Hugh Field have found that horseshoe bats are the likely natural reservoir of the deadly SARS virus that struck southern China in 2002, killing over 700 people and sickening thousands. Originally, a SARS-like virus was found in an animal called the palm civet (a cousin to the "source" of Luak Coffee). When this turned out to be a red herring, Wang and Field placed their bets on bats. Sure enough, SARS-like viruses and antibodies against them showed up in a whole lotta bats, and the finding has been repeated by others around the world.

The duo had good reasons to suspect our flying friends. Bats had already been found to harbor the nasty Hendra and Neepa viruses. And bats have so many disease-harboring and -spreading talents that researcher Kathryn Holmes calls them "magnificent vectors". They're more closely related to humans than you might think (some classify them as primates). They are relatively long lived, a potentially stable home. They huddle together during the day, sneezing and coughing on each other and spreading viruses around, even to other bat species. Then at night, they spread out for miles, potentially spreading disease far and wide. Some even think they can carry diseases without getting very sick themselves. Yikes.

How is it that humans managed to get these diseases? It looks like the sale of bats for food is to blame for bringing folks and flying furballs together. Most Westerners cringe at the thought of eating the critters, but they are prized as food in other parts of the world. The outbreak of SARS is likely due to humans mingling with bats in the crowded markets of southern China.

Now the poor creatures are suspected of spreading the hideous Marburg and Ebola viruses. Could it get any worse? Yes. The eating of giant fruit bats or "flying foxes" on the island of Guam is now blamed for causing one of the most baffling and disturbing epidemics ever-- a sudden appearance of a Parkinson's disease-like syndrome in the 1970's.

The Chamorro people of Guam loved the taste of flying foxes. An American military presence in Guam suddenly made guns more available, and therefore made the delicious giant fruit bats more available too. After downing a flying fox, an aboriginal resident of Guam would drop the whole thing unskinned into a pot of boiling milk. In an hour or so, soup was on. But every scrumptious spoonful was causing cumulative poisoning.

Primitive, fern-like trees called cycads grow on Guam and neighboring islands. These plants produce brightly-colored fruits that often contain neurotoxins. The native peoples ate the seeds, but were wise to the danger, and they therefore washed the seeds thoroughly.

The bats, however, were not so discriminating. They ate the fruits with relish, accumulating toxins in their flesh. And then the Guamians ate them. After downing enough bats, these people started showing tragic symptoms of a new disease christened ALS-PDC. The syndrome was a ghastly amalgam of Alzheimer's-like dementia, ALS-like slow paralysis, and Parkinson's-like shaking. Eventually the disease became the leading cause of death among the adult Chamorro people.

Then just as suddenly, new cases of the disease stopped happening. Turns out that the native bats had been hunted to near-extinction, and different species were being imported from Samoa and other places where no cycads grew. The origin of the disease wasn't worked out until years later, so it remained a deep mystery for decades. The answer was over their heads the whole time-- they merely needed to look up to that leathery flapping sound.

After all of this, bats need a friend. But don't give them a hug. And don't eat them.

Written by Bryan Lowder, posted on 13 January 2006. Bryan is a bioengineer living with his family in Utah. He enjoys imagining that he has hobbies such as microcontroller programming, writing, mushroom culturing, and holography.
DOWNLOADS
eBooks and audiobooks

Further Reading:

Science news article (requires subscription) Guam and ALS-PDC

Related Articles:

The Skyhook The Spanish Flu Epidemic