Onchocerciasis

Onchocerciasis, commonly known as river blindness, is a parasitic disease caused by the filarial nematode Onchocerca volvulus. The infection is transmitted to humans through the repeated bites of infected blackflies (Simulium species), which breed near fast-flowing rivers and streams in tropical regions. The disease is endemic primarily in sub-Saharan Africa, with smaller foci in Latin America and Yemen. Onchocerciasis predominantly affects the skin, eyes, and lymphatic system. When adult female worms residing in subcutaneous nodules (onchocercomas) release millions of microfilariae, these larvae migrate through the skin and eyes, provoking intense inflammatory responses. Key clinical manifestations include severe pruritus (itching), chronic dermatitis with skin changes (such as depigmentation known as "leopard skin," skin atrophy, and lichenification), subcutaneous nodules, and progressive ocular disease. Eye involvement can affect both the anterior and posterior segments, leading to punctate keratitis, sclerosing keratitis, iridocyclitis, optic neuritis, chorioretinitis, and ultimately irreversible blindness. Onchocerciasis is the second leading infectious cause of blindness worldwide. The primary treatment is ivermectin (Mectizan), which effectively kills microfilariae and suppresses their production by adult worms, though it does not kill adult worms outright. Ivermectin is administered as a single oral dose every 6 to 12 months, often through mass drug administration programs. Doxycycline, an antibiotic targeting the Wolbachia endosymbiont bacteria essential for worm survival and reproduction, has shown efficacy as a macrofilaricidal treatment when given over 4 to 6 weeks. Surgical excision of palpable nodules (nodulectomy) may also be performed. Large-scale community-directed treatment with ivermectin, coordinated by programs such as the African Programme for Onchocerciasis Control (APOC), has significantly reduced disease burden in endemic areas.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Onchocerciasis