04 Lymphatic filariasis.pmd

Lymphatic filariasis (LF), also known as elephantiasis, is a major disease of tropical and subtropical regions worldwide. LF is endemic in 80 countries, it is estimated that 120 million people are infected, with one third of them suffering from chronic manifestation of the disease. One billion more individuals are at risk of acquiring the infection [1]. Lymphatic filariasis is a mosquito-borne parasitic disease caused by three nematode worms of the family Filariidae: Wuchereria bancrofti, Brugia malayi and B. timori. Wuchereria bancrofti is responsible for 90% of worldwide infections, with 9% caused by B. malayi in southeast and eastern Asia, whereas 1% result from infection with B. timori in the Pacific region [2]. Bancroftian filariasis is caused primarily by adult worms (known as macrofilariae) that live in the lymphatic vessels. Female worms release embryonic microfilariae (MF) that in many endemic areas are characterized by nocturnal periodicity and thus circulate in the peripheral blood at night (21.00–02.00). The disease is transmitted by Anopheles, Culex and to a lesser extent by Aedes and Mansonia mosquito species. When mosquito vectors feed on infected subjects, they ingest MF along with their blood meal. In the vector, MF develop into infective larvae within 10–15 days. Mosquitoes transmit the infection from person to person. Infective larvae enter the human