Comments
INITIAL SYMPTOMS:
Severe, intractable pruritus, localized papular eruptions, and conjunctivitis; [ID, p. 2370]
FINDINGS:
Adult filarial worms produce microfilariae that migrate through the skin (dermatitis and nodules) and into the eye (visual impairment and blindness). "Leopard skin" pigmentary changes appear on the lower extremities. The skin nodules containing adult worms are called "onchocercoma." Massive enlargement of inguinal and femoral lymph nodes may occur. The disease varies by region probably because of different strains of the parasite: blindness in African savannas and skin disease in forests. [Merck Manual, p. 1347-8; CCDM, p. 438]
SKIN DISEASE:
Sowda is a skin disease that usually affects only one limb, and it is found in Yemen and central Sudan. [CCDM, p. 438] Onchodermatitis has been classified as: 1) acute papular dermatitis; 2) chronic papular dermatitis; 3) lichenified dermatitis; 4) atrophy; and 5) depigmentation. Sowda is a syndrome of hyperpigmented papules and plaques with associated regional lymphadenopathy. The most common symptom in expatriates is itching--an urticaria-like rash is often present on the trunk. Marked eosinophilia is associated with this infection. [Guerrant, p. 742-4, 943] Subcutaneous nodules are about 0.5-3 cm in size and usually detected over bony prominences. These onchocercoma contain the worms that can live for 8-10 years. Sonography can distinguish between onchocercoma and other subcutaneous nodules. [Cecil, p. 2073-4]
EPIDEMIOLOGY:
Travelers at risk are expatriate groups, such as missionaries, field scientists, and Peace Corps volunteers. Blackflies typically bite during the day near flowing rivers. [CDC Travel, p. 271] Local control programs have been very effective; [CCDM]
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