Which clinical specimen is most appropriate for detecting Onchocerca volvulus microfilariae?

Which clinical specimen is most appropriate for detecting Onchocerca volvulus microfilariae?

• A. Urine
• B. Blood smear
• C. Skin snip
• D. Stool

Answer: (C)

Onchocerca volvulus microfilariae reside primarily in the skin and subcutaneous tissues rather than in the bloodstream, so detecting them is best done by sampling skin. A skin snip—a tiny piece of skin taken and incubated in saline to allow any microfilariae to emerge—provides the most reliable direct evidence of infection under microscopic examination. Urine and stool are not expected sources of these microfilariae, and while some filarial infections show microfilariae in blood, Onchocerca microfilariae are not consistently found in peripheral blood, making a blood smear much less sensitive.

Onchocerca volvulus microfilariae reside primarily in the skin and subcutaneous tissues rather than in the bloodstream, so detecting them is best done by sampling skin. A skin snip—a tiny piece of skin taken and incubated in saline to allow any microfilariae to emerge—provides the most reliable direct evidence of infection under microscopic examination. Urine and stool are not expected sources of these microfilariae, and while some filarial infections show microfilariae in blood, Onchocerca microfilariae are not consistently found in peripheral blood, making a blood smear much less sensitive.