Life Cycle

For a complete description of the life cycle of W. bancrofti, please refer to the following diagram and the explanation below:

(Image 7)

1. Infective larvae exit the mosquito vector through the probiscus as the mosquito bites the human host. Mosquito enters the skin of the human host.

2. Infective larvae migrate to the peripheral lymphatics where they can access lymph nodes and lymph vessels. In the nodes or vessels, the larvae matures for a period of 6-12 months. If both males and females are present in the same area, they will mate. Because sexual reproduction occurs in the human, the human is called the definitive host. Adult worms can live in the lymphatic system for up to 10-15 years (Reference 16).

3. After mating, females release sheathed microfilariae that migrate from the lyphatic system to the blood circulatory system. Adult female worms can release microfilariae for 3-5 years, and the microfilariae is able to live within the lymphatic and blood circulatory systems for up to 18 months (Reference 16).

4. Once in the blood circulatory system, the microfilariae is able to be picked up by the mosquito vector through a blood meal taken by the mosquito.

5. The sheathed microfilariae are ingested into the stomach of the mosquito where their sheaths are digested. Once they are unsheathed, the microfilariae bores through the stomach into the body cavity. They migrate to the thoriacic musculature where they mature (Reference 17).

6 & 7. Maturation occurs for a period of 10-14 days. At the end of this period, the microfilariae is now in its infective stage (Reference 16).

8. The now mature microfilariae migrates to the probiscus of the mosquito where it is ready to be injected again into a human host. Because stages of growth occur within the mosquito, it is known as an intermediate host (Reference 16).