Lymphatic filariasis. A woman with her right leg affected by lymphatic filariasis (elephantiasis). She is attending a health education meeting and has been given free soap and antibiotics. Filariasis is caused by parasitic worms spread by blood-sucking insects. The worms invade the lymphatic system producing thousands of larvae that spread around the body. Repeated infection causes inflammation of lymph vessels and accumulation of fluid, which can lead to enormous enlargement of parts of the body (elephantiasis). Treatment is usually with the drug diethyl- carbamazine. Soap, water, and antibiotics to prevent secondary infection can also be effective.