Filariasis

Synonyms

Elephantiasis.

Epidemiology

Tropical and subtropical areas of Asia, Africa, thePacific Islands, several of the Caribbean Islands, and South America.

Definition

Tropical disease, infestation by nematodes, resulting in massive disfiguration by thickening of the skin and underlying tissues.

Aetiology & Pathogenesis

Infestation mostly by Wuchereria bancrofti (90%), which causes, Brugia malayi, and Brugia timori. After a bite of infected mosquitoes, the larvae which have been deposited in the lymphatic system develop into adult worms, blocking the lymphatic vessels, resulting in disfiguring elephantiastic swelling of the extremities, scrotum, vulva, and breasts.

Signs & Symptoms

Hardening of the hyperkeratotic and hyperpigmented, warty skin, which shows folds, fissures and cracks, is swollen, painfull and foul smelling. Recurring acute lymphadenitis with swelling of lymphnodes in the groin and axillae is an immune response to dying adult worms.

Chronic, initially reversible lymphedema, finally leads to elephantiasis.

Elephantiasis is a disfiguring, chronic manifestation and presents months to years after initial infection as severe swelling of the extremities, scrotum, vulva, and breasts. Following treatment acute filarial lymphangitis with small, tender nodules at the site of the dying worms may be seen.

Localisation

Extremities, scrotum, vulva, and breasts.

Classification

Early and late (chronic).

Laboratory & other workups

Antigen released by adult filarial worms can be detected by immunochromatographic test.

Mikrofilariae can be detected in peripheral blood during the early stages of filariasis. Blood eosinophilia.

Dermatopathology

Edematous and fibrotic thickening of the skin with dilated lymph vessels. Dense lymphocytic inflammatory reaction with many eosinophils. In advanced stages, edema gradually resolves and is replaced by fibrosis.

Course

Chronic.

Complications

Superinfection.

Diagnosis

Clinical feature; laboratory findings (see there).

Differential diagnosis

Podoconiosis (‘‘mossy foot’’), which is a noninfectious tropical lymphedema occurring in tropical volcanic highland areas.

Prevention & Therapy

Diethylcarbazine (DEC): 200 mg PO q12h 3 12 days, repeat 10 days later, or 6 mg/kg/day PO 3 12 days (pediatric dose), repeat 10 days later.

Special

DEC is no longer approved by the FDA. Cave use in patients with concurrent onchocerciasis.

10.4.1 Filariasis