Filariasis

A group of tropical diseases, caused by various parasitic worms or their larvae, which are transmitted to humans by insect bites. Some species of worm live in the lymphatic vessels. Swollen lymph nodes and recurring fever are early symptoms. Inflammation of lymph vessels results in localized oedema. Following repeated infections, the affected area, commonly a limb or the scrotum, becomes very enlarged and the skin becomes thick, coarse, and fissured, leading to a condition known as elephantiasis. The larvae of another type of worm invade the eye, causing blindness (see onchocerciasis). A third type, which may sometimes be seen and felt moving beneath the skin, causes loiasis, characterized by irritating and sometimes painful areas of oedema called calabar swellings. The diagnosis of filariasis is confirmed by microscopic examination of the blood. The anthelmintic drugs diethylcarbamazine or ivermectin most often cure the infection but may cause side effects such as fever, sickness, muscle pains, and increased itching. Diethylcarbamazine can be given preventively, and the use of insecticides and protective clothing help to protect against insect bites. (See also roundworms; insects and disease.)