No symptoms
The commonest situation. The parasite is present in the blood and damage is accumulating in the lymphatics, but the person feels and looks well. Damage is already under way.
Lymphatic filariasis
The mosquito bite was thirty years ago. The swelling came later.
Lymphatic filariasis is a parasitic infection that damages the lymphatic vessels and, years later, causes the swelling known as elephantiasis. It is endemic along the Kenyan coast and across much of sub-Saharan Africa. The infection can be cleared. The swelling it leaves still needs treating — and it responds well.
What it is
A mosquito-borne infection by thread-like worms that live in the lymphatic vessels. In Africa the cause is almost always Wuchereria bancrofti.
Infected mosquitoes pass larvae into the skin during a bite. These mature into adult worms in the lymphatic vessels, where they can live for years, widening and scarring the vessels and steadily reducing their ability to drain.
Infection is usually acquired in childhood through repeated bites, and a person can carry it for years while feeling entirely well. The swelling typically appears in adulthood, decades later — which is why so few patients connect their swollen leg to mosquitoes at all.
In Kenya it is concentrated in the coastal counties: Kwale, Kilifi, Lamu, Tana River and parts of Mombasa. Across Africa it remains endemic in many countries, and is one of the neglected tropical diseases targeted for elimination through national mass drug administration programmes.
What matters is where someone grew up, not where they live now. A person raised in Kwale who has lived in Nairobi for twenty years still carries that history in their lymphatics. It is one of the most useful questions in the consultation, and one of the most often skipped.
Lymphoedema is not contagious. Filariasis spreads only through mosquito bites after prolonged exposure in an endemic area. Sharing a home, bed, food or clothing with an affected person carries no risk at all.
What it looks like
Most people with the infection show no visible signs. Among those who develop disease, presentation varies.
Four presentations
Limb swelling
Usually beginning in one leg, often below the knee, and spreading upward over years. The skin thickens and deep folds form. In advanced disease the surface becomes hardened and warty — the appearance described as elephantiasis.
Hydrocele
Fluid collecting in the scrotum, the most common chronic sign in men in endemic areas. Surgery is usually curative. Many men never mention it unless asked.
Genital and breast swelling
Under-reported, rarely volunteered by patients, and treatable. It needs a clinician willing to ask gently and without embarrassment.
Grew up on the coast, and living with a swollen leg? It can be treated — even after many years.
Book an assessmentAcute attacks
Acute attacks make the swelling worse
People with filarial lymphoedema experience sudden episodes of fever, chills and a hot, red, painful limb, usually triggered by bacteria entering through cracked skin or fungal infection between the toes. Each attack causes further permanent damage. A patient having several attacks a year deteriorates steadily, and each episode typically costs days of work. Preventing them is the most effective thing that can be done.
Seek medical care the same day for fever with a hot, painful limb. It needs antibiotics, rest and elevation. Do not apply compression or massage during an attack.
Treatment
Two separate problems: clearing the parasite, and managing the damage it left behind.
Managing established filarial lymphoedema
The World Health Organization calls this morbidity management and disability prevention. It costs very little, can largely be taught to the patient, and reliably reduces both limb size and the frequency of attacks.
Daily washing
The limb washed daily with soap and clean water at room temperature, with careful drying between the toes and inside skin folds. Unglamorous, and the single most important intervention.
Skin and nail care
Treating fungal infection, trimming nails and caring for any crack or cut. Most attacks begin at these small entry points.
Movement and elevation
Regular exercise of the limb and elevation at rest help whatever drainage remains. Simple ankle and foot exercises done several times a day make a measurable difference.
Compression and footwear
Bandaging or compression garments where appropriate, and protective shoes that fit without rubbing. Shoes prevent the small injuries that start attacks.
Where a trained therapist is available, full decongestive therapy adds considerably to this basic programme. Hydrocele is treated surgically.
The tablets
Why taking the tablets did not make the swelling go away
National programmes distribute antiparasitic medicines in endemic districts. They clear the parasite and stop mosquitoes spreading it further, protecting the next generation.
They do not reverse damage already done. Once the vessels are scarred, killing the worms changes nothing about the swelling. That isn't a failure of the tablets, and it isn't the patient's fault. It simply means someone can be free of the parasite and still need lymphoedema care — care that works.
Prevention still matters for everyone else. Sleeping under a treated mosquito net, taking part in mass drug administration when it is offered, and reducing mosquito breeding sites around the home all protect children from acquiring the infection.
Filariasis or podoconiosis?
Both cause elephantiasis of the leg and are often confused.
Where from
Filariasis: hot, humid coastal areas. Podoconiosis: volcanic highland farming areas.
Which limbs
Filariasis: often one leg, may reach the groin. Podoconiosis: usually both legs, below the knee.
Genital swelling
Points to filariasis. Podoconiosis does not cause it.
Blood tests
Filarial antigen testing is positive in filariasis and negative in podoconiosis. Where available it settles the question.
For clinicians and health teams: Dr. Janet Mwau runs lymphoedema training and structured certification for hospitals, county health teams, oncology units and training colleges. Arrange training
Getting help
Filarial lymphoedema is treatable at every stage.
Including after decades, and including in people repeatedly told nothing can be done. Treatment reduces limb size, cuts the number of attacks, and restores the ability to walk and work.