Filariasis is an infectious disease that spreads through mosquito bites. Some people have no symptoms. Others may have inflammation, swelling or fever. Filariasis can lead to lymphedema (fluid retention) or hydrocele (swelling in the scrotum). You can prevent filariasis by avoiding mosquito bites if you live in or travel to tropical climates.
In the most severe cases, it can cause disfigurement, such as thickening skin and swelling in your calves. Because of this disfigurement, some people refer to filariasis as elephantiasis.
You get filariasis through tiny parasitic worms (filarial worms) that infect your lymphatic system. The lymphatic system balances fluid levels and helps protect your body from infections. Healthcare providers sometimes call the condition lymphatic filariasis because it affects your lymphatic system.
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Filariasis is most common in tropical climates. Countries in Asia, Africa and South America have higher cases of filariasis infection. The condition is rare in North America. The worms that cause filariasis don’t live in the United States.
People rarely get a filariasis infection during a short visit to one of these countries. You are more likely to get filariasis if you stay in a high-risk area for months or years.
About 120 million people worldwide — 1.5% of the world’s population — have a filariasis infection.
Filariasis is a parasitic infection with a type of roundworm. Tiny worms, too small to see with the naked eye, invade your body. Under a microscope, the filarial worms look like threads.
There are several types of filarial worms:
About two in every three people who have lymphatic filariasis don’t have severe symptoms. But filariasis usually leads to a weakened immune system.
Some people may experience:
Over time, damage to your lymphatic system may make it difficult for your body to fight infections. Because of this lowered immune response, you may develop:
Filariasis spreads through mosquito bites. When a mosquito bites someone who has filariasis, the filarial worms in the person’s blood infect the mosquito. Then, when the infected mosquito bites another person, the worms pass into that person’s bloodstream.
When these worms enter your bloodstream, they travel to your lymphatic system. There, they grow into adult worms. The adult worms stay alive for up to seven years. The filarial worms reproduce and release millions of worms into your bloodstream.
To diagnose lymphatic filariasis, healthcare providers need to examine a blood sample. They may use:
Your treatment plan varies depending on what symptoms you have and how severe they are. In general, filariasis treatment may include:
If you're taking filariasis medications, you need careful monitoring from a healthcare provider. Anti-parasitic medications can lead to severe side effects. Some of these side effects include:
Even if medication kills the filarial worms, you can still develop lymphedema. To manage lymphedema symptoms, you can:
There's no vaccine or cure for filariasis. Medication can kill many of the worms and keep you from spreading the infection to someone else. Treatment can also reduce filariasis symptoms.
The best way to prevent filariasis is to avoid mosquito bites, particularly in tropical areas. If you live in or travel to places where a filariasis infection is possible, take the following steps to prevent mosquito bites:
In parts of the world where filariasis is common, the World Health Organization recommends treating whole regions with preventive chemotherapy. With this prevention strategy, people at risk of infection take an annual dose of specific chemotherapy medications.
The medications have a small effect on adult worms but can keep younger worms from reproducing. They can also prevent the parasites from spreading to mosquitoes.
Filariasis may develop into chronic conditions such as lymphedema or elephantiasis. These conditions have no cure, although you can manage them and reduce symptoms.
People who have these chronic conditions often experience negative social impacts. If they have very visible, severe symptoms such as extreme swelling, they may experience social stigma. Chronic swelling or pain may also impact a person’s ability to work.
You may also want to ask your healthcare provider:
A note from Cleveland Clinic
Lymphatic filariasis is a parasitic infection. It is common in tropical climates and rare in North America. The disease spreads through mosquito bites. These mosquitos carry small worms that travel through your bloodstream to your lymph system. Many people have no visible symptoms, while others develop chronic inflammation and swelling. A yearly medication may reduce the number of worms in your bloodstream and reduce symptoms. To prevent infection, it’s important to protect yourself from mosquito bites.
Last reviewed by a Cleveland Clinic medical professional on 10/15/2021.
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