By Patrick Foote

Is a nematode. Causes Ochocerciasis or “river blindness” Nematode does not cause blindness, but its endosymbiont Wolbacia pipientis (bacteria) Second leading cause of blindness. Estimated 18 million suffer from Ochocerciasis, and 270,000 cases of blindness.

Taxonomy Kingdom Animalia Phylum Nematode Class Rhabditea Order Spiruida Superfamily Filaroidea Family Onchocercidae Genus Onchocerca SpeciesVolvulus

Hosts Definitive: Humans (only ones) Intermediate: Black fly (Simulium yahense)

Geographic Central and South America. Mainly Africa

Morphology Males are 19 to 42 cm long and 130 to 210 um wide. Females are 33.5 to 50 cm long and 270 to 400 um wide. Infective larvae of O. volvulus are 500 micrometers by 25 micrometers

Life Cycle

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Pathogenesis Adult worm is least pathogenic. In Africa, found in pelvis region. In Americas, it is found above the waist. Sometimes causes enlargement of body parts and “ hanging groin” which loses elasticity in skin. Inflammation, can spread to nearby tissues (eye) Itchy skin Abnormal pigmentation. Bacterial infection

Diagnosis Blood free skin snip (biopsy) Diagnosis is based on symptoms. History of exposure to black flies.

Treatment Treatment and control is done by Ivermectin. Ivermectin is effective in killing larvae, but does not affect adult worm.

Control Vector control (black fly) Treatment of infected patients Avoidance of black fly. OCP “Ochocerciasis Control Program” launched in First tried larvacide on fast flowing rivers to control them. No real effect treatment with Ivermectin for infected people, eliminating it as public concern.

Questions: What is the definitive host of O. volvulus? How do you diagnose O. volvulus? What can this parasite cause? Where is the parasite found?

References: treatments/articles/20195.aspx treatments/articles/20195.aspx me-worms-in-my-eye.html me-worms-in-my-eye.html