Symptoms
Most cases of lymphatic filariasis infection don’t have any symptoms at all. Those infected with the microscopic worms likely aren’t aware that they are infected, but they can still pass on the parasite to others.
When symptoms do occur (often years later), they can lead to extensive disfigurement and disability. These symptoms are permanent and can be so debilitating that they keep people from working. The three most visible and concerning manifestations of lymphatic filariasis are lymphedema, elephantiasis, and hydrocele.
Lymphedema
While many people use lymphatic filariasis and elephantiasis interchangeably, it’s actually lymphedema that gives the appearance of more elephant-like features. Lymphedema is when there is intense fluid collection and swelling in parts of the body, most often in the legs, breasts, or genitals. This inflammation can sometimes be accompanied by fever and be quite painful.
An estimated 15 million people currently live with lymphedema worldwide, and the majority of those who develop this condition do so years after first becoming infected with the parasite.
Elephantiasis
Elephantiasis is when the skin and underlying tissues become abnormally thick. This is often the result of secondary bacterial infections that happen because the body’s lymphatic system is damaged and their immune system is suppressed due to the parasite.
Hydrocele
Some men infected with the parasite develop swelling in their scrotum. An estimated 25 million men worldwide are believed to have hydrocele as a result of lymphatic filariasis.
Tropical Pulmonary Eosinophilia Syndrome
This complication is generally found in infected individuals living in Asia, and consists of shortness of breath, coughing, and wheezing.
Causes
Lymphatic filariasis is caused by three types of microscopic, thread-like worms, namely Wuchereria bancrofti, Brugia malayi, and Brugia timori. The overwhelming majority of cases (90%) are due to Wuchereria bancrofti.
Transmission
Much like malaria, these roundworms spread from person to person through mosquito bites. Several different kinds of mosquito species can transmit the parasite, including Anopheles (which also transmit malaria) and Aedes (which can transmit viruses like dengue and Zika).
Mosquitoes aren’t just carriers, they’re also an important part of the worm’s life cycle. When the insects bite someone who is infected, they take in the immature larvae of the parasite (called microfilariae). For one to two weeks, the larvae go through a transformation inside the mosquito, and when the bug bites someone else, the now-infective larvae get transferred to the skin and make their way into the body.
Once inside, the worms grow into adult worms and cluster in the lymphatic system, sending out microfilariae into the blood stream, which can then be picked up by mosquitoes. And on and on it goes. This can happen even if someone doesn’t have any symptoms, and adult worms can live and reproduce inside the human body for six to eight years.
How the Parasite Affects the Body
The reason the worms can be so destructive in the human body is because they make their home in the lymphatic system. This complex network of organs and tissues is responsible for, among other things, protecting the body from disease and regulating fluid in your tissues.
For these effects to happen, however, you have to be bitten by infected mosquitoes repeatedly, over the span of several months.
Diagnosis
There are two primary ways lymphatic filariasis is typically diagnosed: blood smears or assays.
The worms can’t be seen by the naked eye, but you can catch a glimpse of them under a microscope. This diagnostic method uses a small amount of blood (taken by a finger prick, for example) smeared onto a slide, which is then looked at through a microscope. The worms are only active at night, so the sample should be taken then. This is the cheapest and more practical way to test for the parasite.
Alternatively, serologic testing can also be used for diagnosis. When you’re infected with a parasite, the human body often makes antibodies to try to fight it off. These antibodies can be detected using routine assays done on blood samples. This method, however, tends to be used primarily by public health officials attempting to monitor and map the transmission of the parasite in a given region.
Because many people don’t present symptoms until years after they’re infected, tests might come back negative even if their condition is the result of the parasite.
Treatment
Lymphatic filariasis can be treated and controlled in a number of ways, including medications and vector control.
Medications
To prevent the spread of lymphatic filariasis, a combination of medications are often given routinely and proactively to everyone in a given area—regardless of whether they have been diagnosed with the condition.
While this won’t cure everyone who has lymphatic filariasis or its various complications, it can help prevent the spread of the parasite because it effectively eliminates the microfilariae that can be carried by mosquitoes and passed from person to person.
Side effects of the drugs can sometimes be worse if an individual has co-infections with other diseases, so different regions are recommended to receive different treatment combinations. These include:
Albendazole, on its own in areas with loiasis (or African eye worm)Diethylcarbamazine citrate (DEC), often used with albendazole in areas without onchocerciasisIvermectin, which is primarily used with albendazole in areas with onchocerciasis (or river blindness)In certain areas without onchocerciasis, all three medications might be recommended.
For those already infected with the parasite, DEC or Ivermectin (in areas with onchocerciasis), can be taken to kill the parasite’s microfilariae and some—though likely not all—adult worms.
Some research also indicates that taking 200 milligrams a day of doxycycline can help kill adult worms, though it is not yet a first-line treatment option recommended by the World Health Organization.
Vector Control
Mosquitoes are integral to the transmission of lymphatic filariasis, and other harmful pathogens like malaria, West Nile virus, and dengue fever, so reducing their populations and warding against bites is an important prevention strategy. This can be done by:
Using mosquito nets treated with insecticideSpraying in and around residential areasWearing bug spray with DEET (if available) and long pants and sleeves
While this likely won’t eliminate lymphatic filariasis entirely, it can help reduce the chances someone becomes infected with the parasite.
Coping
The symptoms associated with lymphatic filariasis can often be excruciating, but they can be managed (or prevented entirely) with a few basic strategies:
Practice good hygiene, including frequent hand-washing and cleaning affected areas with soap and water to prevent infections. Elevate swollen body parts. Do light exercise where you move the affected area. Wrap the swollen area snugly with bandages to encourage the draining of fluids. Take any medication recommended by a healthcare provider exactly as prescribed.
Cancer centers often offer therapy for lymphedema that involves specialized wraps and massages.
A Word From Verywell
Lymphatic filariasis is extremely rare in North America and Europe. In order to become infected with the parasite, you have to be bitten by infected mosquitoes repeatedly and over a long period of time. If you’re just making short-term trips to areas where lymphatic filariasis is common, there’s little reason to be concerned about getting sick from the parasite.
