Chapter: Medical Microbiology: An Introduction to Infectious Diseases: Tissue Nematodes

Onchocerca volvulus : Parasitology

The 40- to 60-cm thread-like female adults lie, together with their diminutive male partners.

ONCHOCERCA

Onchocerciasis or river blindness, produced by the skin filaria O. volvulus, is character-ized by subcutaneous nodules, thickened pruritic skin, and blindness.

Onchocerca volvulus : PARASITOLOGY

The 40- to 60-cm thread-like female adults lie, together with their diminutive male partners, in coiled masses within fibrous subcutaneous and deep tissue nodules. The female gives birth to more than 2000 microfilariae each day of her 15-year lifespan. These prog-eny lose their sheaths soon after leaving the uterus, exit from the fibrous capsule, and mi-grate for up to 2 years in the subcutaneous tissues, skin, and eye. Ultimately they die or are ingested by black flies of the genus Simulium, which breed along the banks of turbu-lent, fast-moving streams. After transformation into filariform larvae, they are transmitted to another human host. There they molt repeatedly over 6 to 12 months before reaching adulthood and becoming encapsulated.

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Medical Microbiology: An Introduction to Infectious Diseases: Tissue Nematodes : Onchocerca volvulus : Parasitology |