Wuchereria bancrofti
are parasitic worms that live in humans and cause lymphatic filariasis. This disease, also known as elephantiasis, causes pain and extreme disfigurement because the lymph nodes will become fibrous and extremely enlarged. Radical surgery is the usual way to treat this. This disease also can be caused by brugia malayi, which is a similar type of parasite, but Wuchereria bancrofti are much more common. In 1994, the World Health Organization estimated that about 100 million people suffered from either form of lymphatic filariasis. Because mosquitoes transmit the parasites, the disease is most prevalent in tropical zones where mosquitoes thrive.
Microfilariae
Wuchereria bancrofti begin as microfilariae in the blood of an infected person. The microfilariae are about 0.244 to 0.296 millimeters long and .0075 to .001 millimeters wide. The microfilariae stay at this size and stage until a mosquito bites a human and ingests the microfilariae with the infected blood.
L1 Larvae
Once inside the mosquito, the microfilariae lose a protective outer sheath and then penetrate the mosquito's midgut and enter the thoracic muscles. They then begin to grow and develop into the first larval stage: L1 larvae.
L3 Larvae
The L1 larvae continue to grow and develop in the mosquito until they are L3 larvae, which is when they become infectious to humans. It is at this point that the larvae migrate to the mosquito's proboscis, which is what it uses to bite a human and ingest blood. At the mosquito's next meal, the larvae are injected into the victim and the life cycle continues.
Adults
Once inside the blood of a human, the larvae move to the lymph nodes and begin to grow and develop into adults. This takes about three to 12 months and causes a lot of damage and enlargement of the lymph nodes. Adult females grow to be about 8 to 10 centimeters long and 0.24 to 0.3 mm wide. Males grow to be about 4 cm long and 0.1 mm wide. It can take up to 15 months before symptoms of this disease become evident. The adults can survive in a human for about five to 10 years.
Procreation
Once the Wuchereria bancrofti mature into adults, the males and females are able to mate. The female then gives birth to microfilariae to continue the life cycle. One female can produce millions of microfilariae over her lifetime.
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