Lymphatic filariasis

The disease, which principally afflicts the economically disadvantaged, originates when roundworms of the order Filarioidea are transferred to human hosts by infected mosquitoes and biting flies. After infection, adult worms mature, mate, and reside in the nodes and vessels of the lymphatic system, causing changes that restrict lymph flow. Early symptoms of the disease include fever and transient swelling of the limbs; later stages are characterized by scrotal swelling and permanent swelling of the limbs. The best known symptom of lymphatic filariasis is elephantiasis, a condition of long-standing infection typified by grossly swollen, thick-skinned limbs. Reservoirs for filariasis include humans, monkeys, and domestic cats, although not every reservoir harbors the same strain of the disease. Control of lymphatic filariasis has been attempted through mass or selective treatment of human populations to reduce the parasite reservoir; vector suppression and control; and promotion of personal protection. Methods are usually applied in combination. Unfortunately, the logistical support required for effective vector control is lacking in most endemic areas, although in some areas of southern India the disease has been controlled by community efforts to reduce vector breeding sites. The most common approach to reducing transmission and morbidity has been selective or mass treatment with diethylcarbamazine (DEC). Ivermectin is now a promising alternative to DEC for use in community-based filariasis control programs.