Lymphatic filariasis. People with swollen legs due to severe lymphatic filariasis (elephantiasis). This condition is caused by infection of the lymphatics with parasitic worms of the species Brugia malayi, Brugia timori, or Wuchereria bancrofti. The worm larvae are spread by blood- sucking insects. The worms cause inflammation of the lymph vessels, resulting in localised oedema (swelling). Following repeated infection the affected area - commonly a limb or the scrotum - becomes greatly enlarged and the skin becomes thick and fissured. This condition is called elephantiasis. Drugs may cure early infection.