Elephantiasis. Computer illustration of the leg of a person affected by elephantiasis, also known as lymphatic filariasis, and close-up view of microfilaria in patient's blood. This disease is caused by parasitic nematode worms transmitted in larval form by the bite of mosquitoes. The larvae develop into adult worms (macrofilariae) that lodge in and block the lymphatic system. This causes lymph fluid to accumulate in the limbs, a form of lymphoedema. Elephantiasis is rarely fatal, but causes widespread suffering in tropical regions. Treatment involves drug therapy and rigorous hygiene to prevent skin infections.