Lymphatic Filariasis Patient Information Fact Sheet

What is lymphatic filariasis?
Lymphatic filariasis, commonly known as elephantiasis, is a disease caused by a threadlike worm that can grow and reproduce in the human lymphatic system, an important part of the body's immune system. The worms can live for up to seven years and can block the drainage of the lymph, causing painful swelling of the limbs and scrotum. The worms can also damage the kidneys. The disease can be found in 80 countries in Asia, South/Central America, Africa, and the Pacific Islands. More than 40% of all infected people live in India. The risk to tourists or travelers with short visits is very low.

How do you contract lymphatic filariasis?
The larvae of these microscopic worms are transmitted to humans by the bite of an infected mosquito. A number of different mosquito species can carry the worms, including Culex and Anopheles. Many people never show outward symptoms of infection, but this may result in unknown damage to the kidneys and lymphatic system. Symptoms can take months or years to develop after the initial infection and include swelling of the arms, legs, or other body parts.

How is lymphatic filariasis diagnosed?
Diagnosis involves detecting the parasites in a blood sample. Usually blood samples are taken at night because the microfilariae that cause lymphatic filariasis circulate in the blood at night. Different species of worm may only be detectable at certain times of the day.

How is lymphatic filariasis treated and prevented?
Treatment includes one dose of diethylcarbamazine (DEC) together with either albendazole (Albenza) or ivermectin (Stromectol). This has been shown to remove 99% of the worms present, and the effect lasts for a full year. The treatment needs to be repeated annually if there is continued risk.

Prevention involves reducing the risk of mosquito bites by sleeping under netting covered with repellent and using an effective insect repellent on exposed skin, especially when it is dark outside. Wearing long sleeves and pants at night can also lower the chances of being bitten by a mosquito. Risk is also reduced by treating local communities with drugs that kill the adult worms and interrupting the cycle of transmission. In 2001, the World Health Organization launched a mass treatment program for people in 22 of the most affected countries.

Further information
World Health Organization: www.who.int/lymphatic_filariasis/en/
Centers for Disease Control and Prevention: www.cdc.gov/parasites/lymphaticfilariasis/

Last Reviewed: June 2013