Black Fly – Summarize Spoken Text

PTE SST – Black Fly

Black fly bites cause blindness. Black flies use blade-like mouthparts to slash the skin and feed on blood. Bites are concentrated on exposed areas of skin, especially along the hairline, feet, ankles and arms. They can produce reactions from small red spots with little or no irritation to a lot of irritation and swelling.

The severity of the problem becomes clear when we consider the exposure rate. In West Africa, one person may get ten thousand bites each year. This incredibly high number is what makes the situation so dangerous. It’s not a single bite that causes harm, but the cumulative effect of thousands from infected flies.

The real danger isn’t the bite itself, but a parasitic worm called Onchocerca volvulus that some black flies carry. Volvulus following repeated bites by infected black flies can lead to blindness. The body’s reaction to the parasite’s offspring, called microfilariae, causes the damage. Persons with heavy infections will usually have one or more of the three conditions: skin rash (usually itchy), eye diseases, and nodules under the skin. These flies hide in the skin during daytime and migrate from the skin to the surface at night, which is a result of evolution selection.

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