Mosquitoes have a long tradition of infecting humans with horrible diseases -- old classics like malaria and encephalitis, as well as relative newcomers, like West Nile virus. Another increasingly common and crippling gift from the mosquito to mankind is lymphatic filariasis, more commonly known as elephantiasis.
Though not common in the United States, it's far from unknown around the tropical and sub-tropical world: About 120 million people have been infected by the parasite that causes elephantiasis [source: World Health Organization]. As its name suggests, elephantiasis infection can result in the painful enlargement of a limb, the genitals or the breasts.
When mosquitoes bite an infected person, they pick up the tiny parasitic worm responsible for infection and pass it along to other humans over the next one to three weeks. These worms make the lymphatic system their home, lodging themselves among the lymph nodes and vessels. Over the next five years or so (during which time no outward symptoms may develop), these filarial worms multiply until millions of them infect the body. The real damage caused, regardless of whether or not there is external enlargement of your body parts, is to the kidneys and lymphatic system.
Swollen body parts can be treated largely through careful cleaning -- it reduces infection that has gone unchecked by the compromised lymphatic system. Anti-parasitic drugs can eliminate the adult worms responsible for the ongoing infection.