The spectrum of disease in lymphatic filariasis.

Lymphatic filariasis affects predominantly the poorer sector of a community, who can least afford to have the disease. According to an estimate by the World Health Organization in 1984, more than 90 million people are currently infected. It is postulated that the different disease manifestations of filariasis are caused by different host immune responses. An understanding of the clinical spectrum of lymphatic filariasis is essential for the effective treatment and control of the disease, and for correctly correlating clinical status with host immune responses. The disease should be divided into lymphatic filariasis caused by adult worms and occult filariasis due to hyper-responsiveness of the host against microfilariae. The acute stage of filariasis is characterized by episodic adenolymphangitis, followed by obstructive lesions one or more decades later. In brugian filariasis, adenolymphangitis is most commonly observed at the inguinal region, and elephantiasis predominantly involves the leg below the knee. In bancroftian filariasis, the lymphatics of the male genitalia are frequently affected, leading to epididymo-orchitis and hydrocele. Lymphatic filariasis runs an accelerated clinical course in previously unexposed adult migrants. Occult filariasis is not a disease of public health importance. It is characterized by lymphadenopathy, asthmatic bronchitis, hypereosinophilia, and an increase in the production of antibodies, especially immunoglobulin, against microfilarial antigens.