Lymphatic filariasis is caused by nematodes (roundworms) that inhabit the lymphatic vessels and lymph nodes of a human host. Wuchereria bancrofti, Brugia malayi and Brugia timori cause lymphatic filariasis.
Infective larvae are transmitted by infected biting mosquitoes during a blood meal. The larvae migrate to lymphatic vessels and lymph nodes, where they develop into microfilariae-producing adults. The adults dwell in lymphatic vessels and lymph nodes where they can live for several years. The female worms produce microfilariae which circulate in the blood. The microfilariae infect biting mosquitoes. Inside the mosquito, the microfilariae develop in 1–2 weeks into infective filariform (third-stage) larvae. During a subsequent blood meal by the mosquito, the larvae infect the human host. They migrate to the lymphatic vessels and lymph nodes of the human host, where they develop into adults.