Lymphatic filariasis
Lymphatic filariasis is caused by the filarial nematodes Wuchereria bancrofti or Brugia malayi, transmitted by mosquito bite, producing lymphatic inflammation and obstruction that leads to lymphedema and elephantiasis, confirmed by identifying microfilariae or adult worms and treated with diethylcarbamazine.
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What this article covers
- Overview
Filarial nematode infection of the lymphatics: lymphatic filariasis is caused by the filarial nematodes Wuchereria bancrofti or Brugia malayi, which invade the lymphatic system after transmission by a female mosquito bite.
- Epidemiology
Mosquito-borne, so distribution follows vector range: transmission requires a female mosquito vector, which restricts risk to travelers and residents of mosquito-endemic tropical and subtropical regions.
- Risk factors
Residence or extended travel in an endemic tropical or subtropical region with active mosquito-borne transmission.
- Pathophysiology
Mosquito inoculation: infective larvae are deposited in the skin during a mosquito blood meal and migrate to the lymphatic system.
- Clinical features
Progressive lymphedema (the hallmark finding): swelling of an extremity or the genital region, developing 9 months to 1 year after the infective bite as a consequence of lymphatic obstruction.
- Differential diagnosis
Loiasis: another filarial nematode infection, but transmitted by the Chrysops fly rather than mosquito, producing migratory Calabar skin swellings and a visible conjunctival worm rather than fixed limb lymphedema.
- Diagnosis
Lymphatic filariasis is confirmed by identifying the parasite: microfilariae on a blood smear, or an adult worm identified within an inflamed lymphatic vessel or node, in a patient with a compatible…
- Management
First, screen for coexistent Loa loa or Onchocerca volvulus infection in patients from regions co-endemic for these filarial infections, because diethylcarbamazine can provoke severe reactions in…
- Complications
Elephantiasis: the most disfiguring and disabling complication, resulting from irreversible chronic lymphatic obstruction if infection is not treated before extensive damage accrues.
- Prognosis
Good if treated before extensive lymphatic damage: early antifilarial treatment clears the parasite and can prevent progression to elephantiasis.
- Prevention
Avoid mosquito bites in endemic areas: use insecticide-treated bed nets, protective clothing, and mosquito repellent during residence or travel in mosquito-endemic tropical and subtropical regions.
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Related articles
- Loiasis (Loa loa infection)
Loiasis is a filarial nematode infection caused by Loa loa, transmitted by the bite of the deer fly, horse fly, or mango fly (Chrysops species), producing migratory subcutaneous (Calabar) swellings and a worm visibly migrating across the conjunctiva, treated with diethylcarbamazine after excluding a high microfilarial load.
- Onchocerciasis (river blindness)
Onchocerciasis, also called river blindness, is a filarial nematode infection caused by Onchocerca volvulus and transmitted by the bite of the female black fly, producing chronic pruritic skin disease (onchodermatitis with skin atrophy and depigmentation) and subcutaneous nodules containing adult worms, and standing as a major cause of blindness in endemic rural communities; treatment is ivermectin, repeated every 6-12 months because it kills microfilariae but not adult worms, with careful screening for coendemic Loa loa before dosing.
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Cellulitis is a nonpurulent, spreading infection of the deep dermis and subcutaneous fat, usually caused by beta-hemolytic streptococci, diagnosed clinically and treated with antibiotics alone since there is no collection to drain.