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Life Cycle
of Wuchereria bancrofti:
Different
species of the following genera of mosquitoes are vectors of W. bancrofti
filariasis depending on geographical distribution. Among them are:
Culex (C. annulirostris, C. bitaeniorhynchus, C.
quinquefasciatus, and C. pipiens); Anopheles (A.
arabinensis, A. bancroftii, A. farauti, A. funestus,
A. gambiae, A. koliensis, A. melas, A. merus,
A. punctulatus and A. wellcomei); Aedes (A. aegypti,
A. aquasalis, A. bellator, A. cooki, A. darlingi,
A. kochi, A. polynesiensis, A. pseudoscutellaris, A.
rotumae, A. scapularis, and A. vigilax); Mansonia (M.
pseudotitillans, M. uniformis); Coquillettidia (C.
juxtamansonia). During a blood meal, an infected
mosquito introduces third-stage filarial larvae onto the skin of the human host,
where they penetrate into the bite wound
.
They develop in adults that commonly reside in the lymphatics
.
The female worms measure 80 to 100 mm in length and 0.24 to 0.30 mm in
diameter, while the males measure about 40 mm by .1 mm. Adults produce microfilariae measuring 244
to 296 μm by 7.5 to 10 μm, which are sheathed
and have nocturnal periodicity, except the South Pacific microfilariae which
have the absence of marked periodicity. The microfilariae migrate into lymph and
blood channels moving actively through lymph and blood
.
A mosquito ingests the microfilariae during a blood meal
.
After ingestion, the microfilariae lose their sheaths and some of them work
their way through the wall of the proventriculus and cardiac portion of the
mosquito's midgut and reach the thoracic muscles
.
There the microfilariae develop into first-stage larvae
and subsequently into third-stage infective larvae
.
The third-stage infective larvae migrate through the hemocoel to the
mosquito's prosbocis
and can infect another human when the mosquito
takes a blood meal
.
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