Three species
of Mansonella infect man : M. perstans, M. ozzardi, and M.
streptocerca.
M. perstans inhabits Africa and South
America. M. ozzardi is restricted to areas of South America and the
Caribbean, and M. streptocerca is found in portions of West and
Central Africa.
The symptoms caused by M. perstans and
M. ozzardi are minor and nonspecific.
Both worms live in the abdominal
cavity, where they provoke little or no inflammation.
The only sign of infection is usually
circulating microfilariae.
By contrast, the adult M. streptocerca
lives in the dermis of the upper trunk, shoulders, and arms.
The microfilariae are concentrated
there, but have also been identified in lymph nodes.
Infection by M. streptocerca causes
itching and hypopigmented macules of upper trunk, shoulders and arms.
After treatment with diethylcarbamazine
(a potent filariacide) microfilaria and adult worms degenerate in the
dermis and cause diffuse and focal inflammation.
The diagnosis is made by placing a skin
snip in saline and watching the microfilaria emerge.
The hypopigmented macules of
streptocerciasis must be distinguished from macules of leprosy.
Species of Culicoides, the biting
midges, are intermediate hosts for all three species of Mansonella.
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