Filariasis is caused by an infection with one of the various types of filarial nematodes (round worms). The disease is caused by several species of nematodes of the Filariidae family and is transmitted by blood-feeding arthropods, such as mosquitoes, blackflies, and deerflies. Filariasis comprises several diseases including blindness and disfigurement causing economic, social and personal impairment. The economic loss to a country from filariasis has never been calculated, but it would seem reasonable to assume that it must be considerably greater than the cost of an effective control programme.
Filariasis has infected 80 million people in 76 countries, and 900 million people are at risk of becoming infected. Major foci continue to exist in Africa. Southeast Asia and Oceania. In the endemic foci in tropical Africa, in Yemen, and in Middle and South America, filariasis is estimated to number more than 30 million cases. The disease is relatively severe in Guatemala, Mexico, Venezuela, Brazil, Colombia and Northern Yemen.