Introduction | Lifecycle | Distribution / Map | Treatment | Loiasis
A Cycle of Destruction
Adult O. volvulus parasites live in nodules in subcutaneous, connective, or muscular tissues of infected humans. The female parasite produces offspring known as microfilariae which migrate from the nodules into other tissues.
Microfilariae in the subcutaneous tissues are taken up by a female black fly during a blood meal. During one to two weeks of development in the black fly, the microfilariae transform into third-stage larvae, which migrate to the fly’s mouthparts. The infective third-stage larvae are transmitted to humans when the fly takes its next blood meal.
Once in the human, the larvae take approximately one year to mature into adults that subsequently mate and produce microfilariae, completing the cycle. The adult female can produce millions of microfilariae in her 9-15 year reproductive life.
In early infection mild symptoms, such as itching, occur. With repeated infections, over several years, a person often develops severe dermatitis, subcutaneous nodules, sensitivity to light, diminished vision, and eventually blindness.
|
