Hello student,

With some internet research on the topic of life cycle of Wucheria bancrofti, here is the answer to your query :

Wucheria bancrofti completes its life cycle in two hosts:

Definite host: Human

Intermediate host: mosquito, belonging to genus Culex, Aedes and Anopheles.

Life cycle in Human:

The infection is acquired by the bite of infected mosquito during which L3 larva are deposited on the skin. These are not directly injected into the blood stream. The L3 larva are deposited on the skin near the site of the puncture which when attracted by the warmth of the skin, the larva enters through the puncture wound or penetrates through the skin on their own. The L3 larva after penetrating the skin, reaches the lymphatic channels, settles down at some spot, metamorphose and becomes sexually mature.

The male fertilizes the female and the gravid females discharge microfilariae which usually appear in the peripheral blood in 8-12 month of infection. These micro filariae circulate in the blood for 6 months to 2 years and then die if not taken by mosquito.

Life cycle in Mosquito:

Microfilaria ingested by the mosquito lose their sheath within 2 to 6 hours of their arrival in the stomach. Then they penetrate the gut wall and migrate to the thoracic muscle, where they rest and begin to grow.

In the next 2 days, microfilaria become thick, short sausage shaped with a short spiky tail,  This is the first stage larva L1.

During 3-7 days of time, the larva grows rapidly, moults once or twice. This is the second stage larva L2.

Metamorphosis completes by 10-11days with distinct features such as the tail atrophies to a mere stump and the digestive system, body cavity and genital organs are now fully developed. This is the third stage larva L3. These larva are the infective form which enters the proboscis sheath of the mosquito on or about the 14th day.

When the mosquito bites a man during the blood meal, these larva are released from the tip of proboscis of mosquito and the cycle is repeated.

Development in mosquito takes place within 10-20 days.

Thank you.