Lymphatic Filariasis

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is lymphatic filariasis?

Lymphatic filariasis is an infectious, parasitic disease caused by nematodes (roundworms). The disease is caused by the presence of thread-like worms, called filariae, in the lymphatic vessels and lymph nodes of the body. The lymphatic channels drain excess fluid from the body and play a role in the infection-fighting immune system.

Lymphatic filariasis is transmitted by mosquitoes. A blood meal taken from an infected individual is then injected into an uninfected person. Unlike lifelong residents, travelers to affected regions usually do not accrue sufficient exposure to the parasite to generate the severe complications discussed in this article.

Lymphatic filariasis most commonly occurs in developing countries with a tropical climate. Wuchereria bancrofti, Brugia malayi, and Brugia timori are the specific worms that cause the infection. The larvae enter the body at the time of the mosquito bite and travel to the lymphatic system, where they mature into adult worms. The adult worms can live for years in the lymphatic system, and they produce immature forms that circulate in the blood.

Lymphatic filariasis causes blockage of the lymphatic channels, leading to swelling and eventual scarring of the legs, known as elephantiasis, and in men, to swelling of the scrotum, or hydrocele. These symptoms are extremely disabling. These conditions are also disfiguring, and, in some communities around the world, people with the disease may be shunned.

Globally, the disease affects more than 120 million people. The disease has been eradicated from the United States, with the last known case occurring in the 1920s. Lymphatic filariasis is found in the tropics of Asia, Africa, the Pacific, the Caribbean, and South America. Haiti, the Dominican Republic, Guyana, and Brazil are the affected countries in the Americas. Travelers to affected countries should be vigilant about mosquito protection (Source CDC).

Seek prompt medical care if you notice swelling of your genitals or extremities, or if you have been in an affected area of the world and think that you may have been bitten by a mosquito.

What are the symptoms of lymphatic filariasis?

Common symptoms of lymphatic filariasis

Typically, lymphatic filariasis does not have clinical symptoms, such as flu-like symptoms, fever, or vomiting. In fact, most people with lymphatic filariasis are unaware they have it. In a small percentage of infected people, lymphedema, or swelling, will occur, typically appearing years after the initial infection.

The characteristic swelling can occur in the arms, legs and chest, but also in the genital areas such as the scrotum and penis, where it is very painful. Left untreated, the disease can progress into a hardening and scarring of the tissues of the legs called elephantiasis. This is due to both the buildup of lymph fluid and the impaired ability of the lymph to fight infections, leaving affected people more susceptible to germs and bacteria. By the time people develop elephantiasis, most no longer have active filariae in their body.

Symptoms of lymphatic filariasis include:

  • Hardening and thickening of the skin (elephantiasis)
  • Swelling of the legs, arms, breasts and genitals

Symptoms that might indicate a serious condition

Mosquitos transmit many serious infections, including malaria. If you are traveling to tropical or subtropical areas where mosquitos are prevalent, you may be at risk for potentially serious, even life-threatening conditions. Seek immediate medical care (call 911) if you, or someone you are with, have any of these serious symptoms including:

What causes lymphatic filariasis?

Mosquitos transmit the parasites from person to person, depositing the larvae through the skin from a bite. The larvae enter the lymphatic system and develop into worms over time, typically six to 12 months. These worms can live in their human host for several years, during which millions of immature forms known as microfilariae circulate in the blood. If the infected person is bitten by a mosquito, the mosquito will carry the filariae to another host, continuing the cycle of infection.

What are the risk factors for lymphatic filariasis?

A number of factors increase the risk of developing lymphatic filariasis. Not all people with risk factors will get lymphatic filariasis. Risk factors for lymphatic filariasis include:

  • Residence in tropical or subtropical areas where the disease is endemic
  • Travel in affected regions, although short-term travelers are at lower risk

Reducing your risk of lymphatic filariasis

Avoiding mosquito bites is the best way to reduce your risk of lymphatic filariasis. When visiting affected areas of the world, you can reduce your risk of getting or transmitting lymphatic filariasis through the following actions:

  • Avoiding mosquito bites
  • Sleeping in an air-conditioned room with closed windows
  • Sleeping under a mosquito net
  • Using insect repellant on exposed skin
  • Wearing long sleeves, long trousers, closed footwear (not sandals), and socks

How is lymphatic filariasis treated?

Treatment for lymphatic filariasis depends on whether the infection is active or has progressed to complications.

Treatment for active infections

Diethylcarbamazine (DEC) is the drug of choice for treating lymphatic filariasis. This drug effectively kills the microfilariae.

Treatment for complications

Complications of lymphatic filariasis, such as lymphedema and elephantiasis, cannot be treated with DEC. The drug only kills active microfilariae.

Patients with lymphedema should be referred to a therapist, who can prescribe exercise, as well as maintenance and hygiene measures to prevent further infection.

Hydrocele (swelling of the scrotum) may be treated with surgery to relieve the swelling.

What are the potential complications of lymphatic filariasis?

Although many cases of lymphatic filariasis do not produce symptoms, getting prompt treatment is essential to avoid complications. You can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Left untreated, filarial infection can progress to complications including:

  • Adverse effects of treatment
  • Elephantiasis
  • Hypersensitivity reaction to developing larvae
  • Kidney damage
  • Swelling of the limbs
  • Swelling of the genitals
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 11
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  1. Lymphatic filariasis. World Health Organization.
  2. Lymphatic filariasis. Centers for Disease Control and Prevention.