Cause

Lymphatic filariasis is caused by infection with parasites classified as nematodes (roundworms) of the family Filariodidea. There are 3 types of these thread-like filarial worms:

Wuchereria bancrofti, which is responsible for 90% of the cases

Brugia malayi, which causes most of the remainder of the cases

B. timori, which also causes the disease.

Adult worms lodge in the lymphatic system and disrupt the immune system. The worms can live for an average of 6-8 years and, during their life time, produce millions of microfilariae (immature larvae) that circulate in the blood.

Mosquitoes are infected with microfilariae by ingesting blood when biting an infected host. Microfilariae mature into infective larvae within the mosquito. When infected mosquitoes bite people, mature parasite larvae are deposited on the skin from where they can enter the body. The larvae then migrate to the lymphatic vessels where they develop into adult worms, thus continuing a cycle of transmission.