Onchocerca volvulus; convoluted filaria (river blindness)

Epidemiology: 1) equatorial Africa 2) Saudi Arabia 3) Central & South America 4) infection is transmitted by the bite of the blackfly (Simulium) 5) the blackfly develops along freely flowing rivers & streams, particularly rapids Pathology: 1) infects primary the skin, eyes & lymph nodes 2) infective larvae from the blackfly develop into adults in subcutaneous nodules 3) 7 months to 3 years after infection, the gravid female releases microfilariae that migrate out of the nodule & concentrate in the dermis 4) infection is transmitted when a female blackfly ingests microfilaria from the host's skin 5) males are 3-6 cm in lenth, females 40-60 cm in length 6) adults live up to 18 years, average 9 years 7) damage is induced by microfilariae, not adults 8) inflammatory changes in the skin, with fibrosis & atrophy 9) neovascularization & corneal scarring lead to corneal opacities 10) inflammation in anterior chamber of the eye & posterior chamber of the eye results in anterior uveitis, chorioretinitis & optic atrophy Clinical manifestations: - see onchocerciasis Laboratory: - diagnosis is made by recovery of an adult worm in an excised nodule or of microfilaria on skin snips a) material is incubated in tissue culture medium or saline on a glass slide for 2-4 hours or overnight b) microfilariae emerge from the skin & may be seen under light microscopy c) no sheaths Management: - see onchocerciasis

Properties

KINGDOM: animal PHYLUM: helminth

References

Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 1174