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November 2006, Volume 4, Number 11
Bats in the News - Vampire Bats may Save Lives

Vampire bats do indeed drink blood – although they lap, not suck, it up. To do that, says the Los Angeles Times, the common vampire (Desmodus rotundus) typically settles onto a sleeping horse or cow, creates a tiny wound with razor-sharp teeth and spends up to half an hour lapping up about a tablespoon of blood.
 
But that leisurely meal is possible only because the vampire has in its saliva an enzyme that has been “super-optimized by evolution” to dissolve blood clots, a researcher says. Normally, blood from the small wound would begin clotting within a few minutes, but this enzyme keeps it flowing smoothly.
 
And, scientists believe, that vampire enzyme can do that same thing for human beings: reopen clogged blood vessels so effectively that damage and death from certain kinds of strokes can be prevented, the newspaper reports. Studies with human patients are under way at 80 medical centers in Europe, Australia, Canada and the United States.
 
Early development of the drug – n genetically engineered version of the vampire-saliva enzyme called desmoteplase – was described in “The Vampire’s Gift” in the Spring 2003 issue of BATS magazine. Only three of more than 1,100 bat species are vampires; all live in Latin America and only one feeds on mammals.
 
The clot-busting drug is designed for emergency treatment of ischemic stroke, in which the blood supply to the brain is choked off. The only currently available clot-dissolving drug (called tPA) is helpful only within the first three hours after a stroke, the Times said, and just 3 percent of stroke victims reach a hospital in that time frame. Desmoteplase seems to extend that crucial window to nine hours and, according to initial human and animal tests, to have fewer side effects than tPA.
 
The hope, writes reporter Regina Nuzzo, is that “desmoteplase acts to dissolve only the clotted area [that is] blocking blood flow to the brain and causing stroke – thus leaving fragile blood vessels in the brain intact.”
 
The drug is being developed by Paion in Germany and Forest Laboratories in New York. The U.S. Food and Drug Administration has granted “fast-track status” to the approval process because it is aimed at unmet medical needs. In the United States, about 700,000 people a year suffer strokes and about 20 percent of them die within a month.
 
The human trials are not complete and results are not available, but previous, smaller clinical studies were very promising.
 
Dr. Wolfgang Söhngen told the newspaper that desmoteplase was optimized by evolution, not scientists. “If vampire bats were not good at feeding on blood, they would have disappeared. The enzyme’s only job is to break up clots.”
 
And that is the life-saving gift that the much-despised vampire bat may give to humans.
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All articles in this issue:
A Dutch Bat House
In America, the Dutch like to say, “everything is bigger.” The cars are longer, skyscrapers are taller, even some of trees ...

Bat Conservation in Canada
Crouching in a low, hot attic, balanced on the rafters, I shined my red-filtered flashlight into the crevice between the chimney ...

Bats in the News
Vampire bats do indeed drink blood – although they lap, not suck, it up. To do that, says the Los Angeles Times, the common ...



Unless otherwise noted, all images are copyright ©Merlin D. Tuttle and/or ©Bat Conservation International