Sasabonsams are vampiric, spindle-legged creatures native to Nigeria. The Nigerian National Quidditch team uses them as mascots. At the 2014 Quidditch World Cup, the Sasabonsams became one of the creatures to attack, becoming frenzied due to the spilled blood.
Myths of the Sasabonsam, a vampire-like being, originated in West Africa.
Sasabonsams are vicious, blood-thirsty, uncontrollable creatures, so why would a Quidditch team choose them as mascots? Oh wait, it's Quidditch ... witness this comment from Rowling's interview with Raincoast Books:
Q: What do you most like about Quidditch?
JKR: That would probably be the violence. (RC)