Lymphatic filariasis. Woman with a swollen leg due to severe lymphatic filariasis (elephantiasis). This condition is caused by infection of the lymphatic system with parasitic worms such as 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 (fluid accumulation and swelling). Following repeated infection the affected area becomes greatly enlarged and the skin becomes thick and fissured. A course of anthelmintic drugs (typically diethylcarbamazine) usually clears up the infection.