Filariasis, Lymphatic

Description

Lymphatic filariasis is caused primarily by adult worms (filariae) that live in the lymphatic vessels. The female worms release microfilariae that circulate in the peripheral blood and are ingested by mosquitoes; thus, infected mosquitoes transmit the infection from person to person. The two major species of filariae that cause lymphatic disease in humans are Wuchereria bancrofti and Brugia malayi.

Occurrence

Lymphatic filariasis affects an estimated 120 million persons in tropical areas of the world, including sub-Saharan Africa, Egypt, southern Asia, the western Pacific islands, the northeastern coasts of South and Central America, and the Caribbean Islands.

Risk for Travelers

Short-term travelers to endemic areas are at low risk for this infection. Travelers who visit endemic areas for extended periods of time and who are intensively exposed to infected mosquitoes can become infected. Most infections seen in the United States are in immigrants from endemic countries.

Clinical Presentation

Most infections are asymptomatic, but the living adult worm causes progressive lymphatic vessel dilation and dysfunction. Lymphatic dysfunction leads to lymphedema of the leg, scrotum, penis, arm, or breast, which can increase in severity as a result of recurrent secondary bacterial infections. Tropical pulmonary eosinophilia is a potentially serious progressive lung disease with nocturnal cough, wheezing, and fever, resulting from immune hyperresponsiveness to microfilaria in the pulmonary capillaries.

Prevention

No vaccine is available, nor has the effectiveness of chemoprophylaxis been well documented. Protective measures include avoidance of mosquito bites through the use of personal protection measures (see Protection against Mosquitoes and Other Arthropods).

Treatment

The drug of choice for treatment of travelers with W. bancrofti or B. malayi infections is diethylcarbamazine (DEC). DEC, which is available to U.S.-licensed physicians for this purpose, can be obtained from the CDC Parasitic Diseases Drug Service at 404-639-3670. (See Immunobiologics Distributed by The Centers for Disease Control and Prevention from the CDC Drug Service.) DEC kills circulating microfilaria and is partially effective against the adult worms and tropical pulmonary eosinophilia. Many patients with lymphedema are no longer infected with the filarial parasite and do not benefit from antifilarial drug treatment. For chronic manifestations of lymphatic filariasis, such as lymphedema and hydrocele, specific lymphedema treatment (including hygiene, skin care, physical therapy, and in some cases, antibiotics) and surgical repair, respectively, are recommended. Travelers should be advised to consult an infectious disease or tropical medicine specialist.

— David Addiss