Happy Halloween – I posted this a few years ago. However, as Halloween comes around every year, it is good to be reminded that coagulation has a more exciting side linked to vampires, werewolves and Dracula.
Vampires, Dracula teeth and bats have become synonymous with the decorations for Halloween. However, the story behind Dracula and vampires is interesting and goes back to the middle ages, possibly linked to a rare blood disorder. It is not entirely clear where the story of the vampires came from. There are some theories that the myths of vampires arose during the Black Death or plague. One of the symptoms of the plague was bleeding from the mouth.
The vampire became part of literature when Bram Stoker wrote Dracula in 1897. Some of his inspiration for his book is believed to come from the story of Prince Vlad Tepes, a member of the Romanian Royal Family. Transylvania is in central Romania. Vlad ruled during the 14th century and was a member of the order of the Dragon, called Dracul in Romanian (derived from Draco, the Latin for dragon). Vlad was a particularly bloodthirsty ruler and enjoyed impaling his enemies on wooden stakes. Possibly this is where Stoker got the idea of a wooden stake through the heart to kill a vampire.
Some of the mythology about the appearance of vampires possibly comes from the features of a rare blood disorder called Congenital erythropoietic porphyria. This is an inherited disease and is extremely rare but has been reported in central Europe. The condition probably arose due to inbreeding amongst the nobility. The valleys of Transylvania is one place where cases have been reported.
People suffering from porphyria have severe light sensitivity and become disfigured from scarring. As a result, they tend to only go out in the dark. Other features include shrunken gums making their canine teeth more prominent, discoloured red teeth, called erythrodontia, increased hair growth (werewolf myth) and red urine. One of the most debilitating symptoms of this condition is abdominal pain. This is made worse by eating certain foods, particularly the chemicals in garlic, hence the vampire’s aversion to garlic. Surprisingly one thing that helps their symptoms is drinking blood. The haem pigment in the blood can survive the gastric acid and is absorbed in small amounts, and relieves the condition.
Bats have also become linked to Halloween, particularly the vampire bat, as this animal lives on blood, including human blood.
Vampire bats feed in total darkness. They have specialised hearing to identify sleeping breathing animals and a temperature sensor in the nose to find the site where the blood vessels are closest to the skin’s surface. Some species only feed on the blood of mammals. The bat has razor-sharp front teeth. It feeds by making an incision in the skin and then laps the blood from the incision. The link between vampire bats and blood clotting is in the bat’s saliva.
The saliva contains several chemicals; some act as anticoagulants, some numb the site of the bite, and one is a clot-buster drug that breaks down blood clots. A protein discovered in the 1990s was called Draculin and was partially characterised and shown to inhibit two of the clotting factors in the clotting pathway. More recently, the true nature of this protein is less certain.
As well as an anticoagulant to stop clotting, the bat saliva also contains a clot-busting chemical that breaks down blood clots to keep the blood flowing. It also enables the bat to regurgitate unclotted blood to feed their young. This chemical, called Desmoteplase, has the most potential for use in clinical practice. It is more active than tPA, the standard treatment widely used to treat heart attacks and strokes. Unfortunately, the results of three clinical trials using the drug to treat stroke did not show a benefit over placebo. As a result, the company involved is no longer developing the drug.