Your Guide to
Neglected Tropical Diseases

Lymphatic filariasis is a parasitic disease spread by mosquitoes in tropical and subtropical regions. Once contracted, the parasites cause lymphatic vessels-where they reside-to dilate and become deformed, leading to the stagnation of lymph fluid. In endemic areas, many people become infected during childhood; however, the disease has a long asymptomatic period, and it can take several years-or in some cases, several decades-for severe symptoms to appear.

Without treatment, lymphatic filariasis causes permanent disability through massive swelling of the limbs, breasts, and genitals (a condition historically known as elephantiasis). Patients face chronic pain, repeated infections, loss of mobility, social stigma, and difficulty working or attending school. Beyond visible deformities, many infected people suffer hidden damage to their lymphatic system and, in some cases, their kidneys. This damage progressively worsens their health and quality of life.

Different types of mosquitoes spread lymphatic filariasis in different parts of the world. The transmission cycle starts when a mosquito bites an infected person and picks up tiny worm larvae (microfilariae) from their blood. The larvae develop inside the mosquito’s body over a period of approximately two weeks, after which they enter the host’s body when the mosquito bites another person.

Once inside the body, the larvae develop into adults in locations such as the lymphatic plexus within the pelvis. They survive for around five to eight years, during which they continue to produce millions of new larvae, repeatedly damaging the lymphatic system and causing chronic inflammation and bacterial infections.

Geographic scope:

• Documented in more than 70 countries worldwide.
• Over 35 countries still require preventive treatment programs.
• Sub-Saharan Africa bears 80% of the global disease burden.
• Other affected regions: South and Southeast Asia, Pacific Islands, Caribbean, South America.

Population affected:

• More than 650 million people live in endemic areas requiring treatment.
• More than 40 million people are estimated to have active infection.

Lymphatic filariasis can be prevented through mass drug administration with medicines (albendazole, diethylcarbamazine, ivermectin) made available through WHO's elimination program. Since 2000, over 10 billion treatment courses have been delivered. A triple-drug regimen (IDA) accelerates elimination, achieving transmission interruption in 2-4 years versus 5+ years with two-drug therapy, but mosquito control, sanitation, and clean water are essential to prevent reinfection.

For those with swollen limbs, daily washing, elevation, and wound care reduce painful attacks and can reverse early swelling. Surgery helps some patients, but access is limited.

More than 25 countries have eliminated the disease.