LYMPHATIC FILARIASIS

Lymphatic filariasis is a parasitic disease caused by microscopic, thread-like worms. There are three different species that can infect humans. Most of the infections worldwide are caused by Wuchereria bancrofti. In Asia the disease can also be caused by Brugia malayi and Brugia timori. The infection spreads from person to person by mosquito bites. The adult worm lives in the human lymph vessels where it mates and produces millions of microscopic worms also known as microfilariae. These circulate in the person's blood and infect the mosquitoes when they bite, and they pass the infection to other people. Adult worms can live for five to seven years. Many bites over several months to years are needed for infection to occur so travelers to these areas are normally at low risk.
The parasite damages the lymph system. People with active infection may have fever, chills, headache and skin lesions while many show no symptoms at all. If the infection goes untreated then complications like lymphedema and elephantiasis can develop. This is caused by fluid collection due to improper functioning of the lymph system as a result of damage from the infection. The swelling usually affects the legs but can also affect the arms, breasts and genitalia. The swelling and the reduced function of the lymph system make it harder for the body to fight infection so these people are more prone to bacterial infections in the skin and lymph system. Good skin hygiene and exercise can help prevent this. When the skin hardens and thickens it is called elephantiasis. Men can develop swelling of the scrotum, called a hydrocele. People can also develop a complication called tropical pulmonary eosinophilia. This causes cough, shortness of breath, and wheezing and occurs more commonly in those infected in Asia.
Diagnosis is confirmed using blood collected at night that is stained with Giemsa or hematoxylin and eosin and examined under the microscope for detection of microfilariae. People with active infection also have increased levels of antifilarial IgG4 which can also be detected in the blood. People with lymphedema often test negative because these complications often develop years after an active infection.
Treatment is with albendazole and ivermectin or with diethylcarbamazine (DEC). Doxycycline has also shown effectiveness. Treatment is only given to those with active infections. Patients with complications for untreated infections should be treated symptomatically. Patients with lymphedema and elephantiasis benefit from good hygiene, exercise and wound management. Patients with hydrocele normally require surgical management.
The best prevention is to avoid mosquito bites. These mosquitoes typically bite between dusk and dawn. You should sleep in an air conditioned room if possible under a mosquito net. Wear long sleeves and pants when out at night and use mosquito repellent on unprotected skin. In some areas that are highly endemic annual mass treatment with antifalarial medications is given.