What is Lymphatic Filariasis?

Lymphatic filariasis is a disease that is caused by microscopic roundworms and is spread by mosquitoes. It damages the lymphatic system and sometimes causes excessive swelling in one or more parts of the body. Affected people might become permanently disabled, depending on the severity of the infection.

The disease is primarily found in the Pacific Islands, South America, the Caribbean islands and South Asia, with the heaviest epidemics in Africa and India. The United States saw occasional outbreaks of lymphatic filariasis before 1900. The disease had disappeared from the U.S. by the early 20th century.

The adult roundworms that cause lymphatic filariasis live in human lymph vessels, but their offspring, called microfilariae, live in the bloodstream. Mosquitoes become infested with the larvae when they bite infected human hosts. They pass the worms to other human hosts as they feed.

The disorder mainly affects adults and is more common in men than in women. It is most prevalent among poor people who live in rural areas or slums. The disease sometimes causes permanent physical disability and renders its victims unable to work, perpetuating the cycle of poverty.

The symptoms begin to develop five to 18 months after a person is bitten by an infected mosquito. Many people who are infected do not develop external or visible signs of the disease, but on the inside, the worms cause serious damage to their kidneys and lymphatic systems. Some people also develop respiratory conditions.

People who have been infected with lymphatic filariasis for many years might develop a condition called lymphedema. Fluid collects in a part of the body such as the legs, arms, breasts or genitals, causing swelling. The affected body part often becomes enlarged or deformed. The skin thickens and hardens from frequent bacterial infections.

Individuals who suffer from this condition, also called elephantiasis, are socially stigmatized in many parts of the world. Family members and friends sometimes refuse to associate with infected people. Men sometimes suffer from permanent damage to the genitals, and women with elephantiasis might be considered unsuitable or ineligible for marriage.

Doctors diagnose lymphatic filariasis by taking a blood smear and examining the sample under a microscope. The worms are most active at night, so the physician might schedule the blood test during the evening hours. The doctor might also look for elevated levels of immunoglobulin G4 (IgG4), which are antibodies in the blood.

Medications such as albendazole, ivermectin and diethylcarbamazine kill the parasites, but they do not reduce the swollen part of the body. Pressure bandages and exercises can help limit the swelling caused by lymphedema. Patients who have lymphedema should wash regularly with soap and water to avoid contracting bacterial infections.