Filarial nematodes Wuchereria bancrofti, Brugia malayi, and B. timori.
Through the bite of infected Aedes, Culex, Anopheles, and Mansonia mosquitoes.
Found in sub-Saharan Africa, Egypt, southern Asia, the western Pacific Islands, the northeastern coast of Brazil, Guyana, Haiti, and the Dominican Republic. Travelers are at low risk, although infection has been documented in long-term travelers. Most infections are seen in immigrants and refugees.
Most infections are asymptomatic, but lymphatic dysfunction may lead to lymphedema of the leg, scrotum, penis, arm, or breast years after infection. Acute episodes in people with lymphatic dysfunction are associated with painful swelling of an affected limb, fever, or chills due to bacterial superinfection. Tropical pulmonary eosinophilia is a potentially serious progressive lung disease that presents with nocturnal cough, wheezing, and fever, resulting from immune hyperresponsiveness to microfilariae in the pulmonary capillaries.
Microscopic detection of microfilariae on an appropriately timed thick blood film. Determination of serum antifilarial IgG is also a diagnostically useful test. This assay is available through the Parasitic Diseases Laboratory at the National Institutes of Health (301-496-5398) or through CDC (www.dpd.cdc.gov/dpdx; 404-718-4745; firstname.lastname@example.org). Microfilariae are usually not detected in patients with tropical pulmonary eosinophilia. Diagnosis requires epidemiologic risk and filarial antibody testing.
The drug of choice, diethylcarbamazine, can be obtained from CDC under an investigational new drug protocol. Patients with lymphedema and hydrocele can benefit from lymphedema management and, in the case of hydrocele, surgical repair.