Life Cycle of Lymphatic Filariasis
Lymphatic filiariasis---also known as elephantiasis---is a parasitic infestation by microscopic worms of the human lymph system. According to the World Health Organization, the parasites Wuchereria bancrofti and Brugia malayi have infected more than 120 million people with lymphatic filiariasis, most of them in Africa and Asia. Symptoms include skin thickening and damaged lymphatic function leading to fluid accumulation in the legs, breasts, genitals and arms. Lymphatic filiariasis has a four-stage life cycle.
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Stage One
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The University of Georgia's Microbiology Laboratory states that the lymphatic filariasis life cycle begins when adult females give birth to live larvae within the lymph nodes of a human host. The larvae---which are born with sheaths protecting them from the host's immune system---then migrate from the lymph nodes into the bloodstream.
The larvae remain in the host's lung arterioles (small blood vessels) during the day. They move to the peripheral blood vessels in the head, neck, abdomen, hands, lower legs and feet at night, concentrating in the peripheral blood vessels from 10 p.m. to 2 a.m. The mosquitoes they need to carry them to new hosts are most active during those hours.
Stage Two
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The second stage of the lymphatic filiariasis cycle begins when a mosquito bites a host. The larvae enter the mosquito's stomach and lose their sheaths. They move through the mosquito's digestive tract walls to its thorax, where they burrow into muscle tissue. The larvae continue to develop for about two weeks before migrating to the mosquito's mouth.
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Stage Three
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When the infected mosquito bites a victim, it releases the larvae into the bloodstream, where they travel to the nearest lymph node. The larvae develop into adults over the next three to 12 months.
Stage Four
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After mating within the lymph nodes, the female adults give birth to a new generation of larvae. These parasites remain undetectable for eight to 12 months. Left untreated, they can survive within a host for up to 10 years.
Treating Lymphatic Filariasis
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Three medicines---diethylcarbamazine, ivermectin and albendazole---are used to treat the infestation. According to Boston College, two of the drugs are administered simultaneously. Either the ivermectin or the diethylcatbamizine targets adult worms and is given as a single dose with albendazole to eradicate the larvae.
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References
Resources
- Photo Credit Centers for Disease Control and Prevention
