As a rule, the vampire bat takes in up to 50g of blood a day. That consumption is not like sitting down to lunch at McDonald’s. The process is slow, and takes hours. How then, do they manage to keep the blood flowing, when their victims’ systems (generally cows or donkeys in South American countries like Brazil) are pumping out clotting factors into the tiny wounds?

Protein in the bat’s saliva keeps the blood liquid and mobile, until they are done the meal. When their fangs withdraw, the wound seals. Researchers who delved into the structure of that protein, came up with the drug desmoteplase, currently manufactured in Germany by the Paion company, and under study in 16 American institutions.

The drawing card for the duplicated "bat spit", is the expanded time frame for treating stroke victims. Currently the only approved drug for immediate use, is IV t-PA, which must be administered within three hours of the onset of symptoms. Desmoteplase, widens that window of opportunity to nine hours, which could mean the difference between life and death, or crippling and total recovery.

So promising is the drug, that the American Heart Association named it to their top ten list of advances in cardiac/stroke medicines for 2003.