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Lymphatic Filariasis

Introduction

Filariasis affecting both legs.

Lymphatic filariasis, commonly known as elephantiasis, is a devastating parasitic infection that is caused by the worm Wuchereria Bancroft and spread by infected mosquitoes.More than 1 billion people in approximately 80 countries live at risk of contracting lymphatic filariasis (LF).

More commonly known as elephantiasis, LF is a devastating parasitic infection spread by mosquitoes. Currently over 120 million people are already infected, with more than 40 million incapacitated or disfigured by the disease.

About 90% of the filariasis infections occur in Africa, Asia, the Pacific Islands, and the Americas. The remaining 10% of the infections are caused by the worm Brugia malayi and occur in Asia and some Pacific Islands.

Photomicrograph of microfilaria.

How Filariasis is transmitted

Filariasis is not transmitted by direct human-to-human contact. It is spread through the bite of nfected mosquitoes in the following sequence.

When a mosquito bites a human to take a blood meal, immature parasitic worms known as microfilariae, are deposited on the surface of the skin. These microfilariae are so small they cannot be seen without magnification.
The microfilariae enter the skin and find their way into lymphatic vessels. Here, during the next 6 to 12 months, they develop into adult worms.
These adult worms live within the lymphatic vessels of the victim from 5 to 10 years. The adults mate here and the females release millions of microfilariae that live in the bloodstream .
When mosquitoes feed on individuals with microfilariae in their blood, these mosquitoes take up the microfilariae with their blood meal. These microfilariae develop within the mosquito for 7 to 10 days.
When the mosquito takes another human blood meal, the microfilariae are deposited on the skin of the new host and the cycle continues.

Symptoms of Filariasis

There are seven stages of filariasis progressing ranging from stage 1, which is slight swelling, to stage 7 in which the individual is severely disabled.

Swelling, which can affect almost all body parts, is the first symptom of this condition.
The very large swollen leg with folds of tough skin is characteristic of the later stages of the disease. This stage is commonly known as elephantiasis.
In stage 6, knobs and mossy lesions that cause the swollen feet and legs to look almost like a tree trunk are present.
By stage 7, the individual is no longer able to care for himself.

The Prevention of Filariasis

This condition can be cured, or prevented, through two major drugs that are used to kill the microfilariae in the blood. These medications are diethylcarbamazine (DEZ) and ivermectin.

A single dose of this medication kills microfilariae and keeps the blood free of them for up to a year. This prevents the spread of the disease but does not cure the infected individual.
Annual treatment must be continued for 5 to 10 years or until all of the adult worms within the individual have died.
Another way to eliminate filariasis is for everyone in an affected community to use salt that is fortified with diethylcarbamazine (DEZ) daily. When this fortified salt is used, instead of regular table or cooking salt, everyone gets a small dose of the medication every day. These small doses are enough to clear the blood of microfilariae.

References

[1] Global Alliance to Eliminate Lymphatic Filariasis 2009. This is a group of public health and charitable organzations working together to eliminate this condition.

[2] WHO Lymphatic Filariasis

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Category: What is Lymphedema? Updated: 2010-02-09

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