Filariasis

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Photo by: Garry DeLong

Filariasis (fih-luh-RYE-uh-sis) is a tropical disease caused by tiny worms.

What Is Filariasis?

Filariasis is caused by different species of microscopic parasitic ^* roundworms that are passed to people through the bites of insects, most commonly mosquitoes. Several strains ^* of these worms, known as filariae (fih-LAIR-e-e), can infect humans, including Wuchereria bancrofti (vooker-E-re-ah ban-CROFT-e). There are also different types of filariasis itself, including cutaneous (kyoo-TAY-nee-us) or skin-related, body cavity, and lymphatic ^* infections. In the cutaneous disease, the worms live in the layers of the skin; in body cavity filariasis, they inhabit certain body openings and surrounding tissue; and in the lymphatic form of infection, they invade the vessels of the lymphatic system and the lymph nodes ^* .

Lymphatic filariasis, which can progress to a condition called elephantiasis ^* , is the most serious form of the disease. It begins when an infected female mosquito injects worm larvae ^* into a person's blood while feeding. The larvae travel to the lymphatic vessels, where they grow into adult worms. As adults, the worms can survive and reproduce for up to 7 years. The gradual buildup of worms in the vessels hinders the lymphatic system's ability to fight infection, and causes lymph fluid to collect—typically in the arms, legs, breasts, and male genitals—leading to swelling and disfigurement.

How Common Is the Infection?

Filariasis is most common in tropical and subtropical regions, including parts of Africa, the western Pacific, Asia (especially India), and Central and South America. In these areas, the number of cases of filariasis continues to rise. It is estimated that more than 120 million people worldwide have the lymphatic form of illness today, and approximately 40 million of them have been disabled or disfigured by the disease. Although contracting filariasis is not a risk in the United States, some recent immigrants may have it, and people who have traveled to other countries can contract the disease as well. Missionaries and Peace Corps volunteers are considered to be most at risk.

Is Filariasis Contagious?

The disease does not spread from direct person-to-person contact. Instead, it is transmitted by the bite of a mosquito. When one of these insects bites someone who is infected, it takes in the parasites along with its meal of blood. The mosquito then can pass those parasites on to the next person it bites. Usually, someone must be bitten many times, typically over a long period, to develop symptoms of filariasis.

What Are the Signs and Symptoms
of the Disease?

The lymphatic form of filariasis usually produces fever, swollen or painful lymph nodes in the neck and groin, pain in the testicles ^* , and swelling in the limbs or genitals. Males and the male urinary and genital systems are particularly likely to be affected. In elephantiasis, a severe form of chronic ^* lymphatic filariasis, the blocked flow of lymph causes one or both legs to swell significantly. Over time, the skin on the leg also can change, taking on a rough texture so that it resembles the skin of an elephant. Although elephantiasis is unusual, up to half of all men with lymphatic filariasis may show serious symptoms, such as swelling of the scrotum ^* . In some cases people may have no obvious symptoms, but they still may have serious damage to the kidneys and lymphatic system.

Lymphatic filariasis can progress to elephantiasis, a swelling and thickening of body tissues from accumulation of fluid. The skin may look thick, pebbly, and dark.

Phototake

Making the Diagnosis

Knowing that the person lives in or has spent time in a country where filariasis poses a risk can help a doctor diagnose the disease. The doctor may also take skin and blood samples from the patient to look for signs of the parasite.

What Is the Treatment for Filariasis?

Ideally, treatment begins as soon as possible after the patient becomes infected. Prompt treatment may not be possible, however, because the disease can be difficult to detect in its early stages. When the diagnosis is made, treatment may include:

• medication to kill the young worms in the bloodstream and stop the parasite's life cycle (although the medicine cannot kill adult worms)
• exercising and moving swollen limbs to improve lymph flow
• bed rest and compression bandages to treat swelling
• medications to lessen swelling and discomfort
• hospitalization and intravenous ^* (IV) antibiotics for secondary infections that might appear because the damaged lymphatic system is less able to assist in defending the body against infectious agents
• surgical treatment for deformities, such as enlarged limbs and scrotum, sometimes with several procedures and skin grafts ^* to correct cases of disfigurement

How Long Does the Disease Last and
What Are the Complications?

Filariasis can last a lifetime, and without treatment it can worsen. The disease can lead to permanent disfigurement and damage to the lymphatic system and kidneys, secondary infections, hardening and thickening of the skin, and sexual and psychological problems. In countries where the disease is common, a serious social stigma ^* often accompanies it.

Can Filariasis Be Prevented?

There is no vaccine to prevent filariasis, but controlling the populations of blood-sucking insects, especially mosquitoes, can limit the spread of the disease. In some areas where filariasis is common, people are treated yearly with preventive medicine to kill any immature worms in their blood. To protect themselves, people can also:

• Stay inside as much as possible from dusk to dawn, when mosquitoes are most active.
• Sleep under mosquito netting.
• Place screens in all windows.
• Use insecticides around living areas.
• Apply insect repellent to exposed skin.