Lymphatic filariasis (elephantiasis): symptoms, causes and care

NHS 111 Wales explains that lymphatic filariasis is a parasitic disease caused by microscopic, thread-like worms. The adult worms live only in the human lymphatic system and block the drainage of lymph. The World Health Organization (WHO) says it is commonly known as elephantiasis and is classed as a neglected tropical disease.

The lymphatic system is described by the NHS as a network of channels and glands throughout the body that helps fight infection and remove excess fluid. When it does not work properly, fluid builds up in the tissues, which is called lymphoedema. A University Hospitals Plymouth NHS Trust patient leaflet describes filariasis as a rare tropical parasite infection that invades and blocks the lymphatics and says this is the commonest cause of lymphoedema worldwide, though the parasites do not live in Great Britain.

According to the WHO, there are three types of the thread-like filarial worms: Wuchereria bancrofti, which is responsible for 90% of cases, Brugia malayi, which causes most of the remainder, and Brugia timori. Adult worms nest in the lymphatic vessels, and can live for approximately 6 to 8 years, producing millions of immature larvae called microfilariae that circulate in the blood.

Mosquitoes become infected by ingesting microfilariae when they bite an infected person. The microfilariae mature into infective larvae within the mosquito, and when infected mosquitoes bite people, mature larvae are deposited on the skin and can enter the body. The WHO says that different types of mosquito are involved, including Culex in urban and semi-urban areas, Anopheles mainly in rural areas and Aedes mainly in endemic Pacific islands.

The WHO says lymphatic filariasis infection involves asymptomatic, acute and chronic conditions. The majority of infections are asymptomatic, with no external signs, yet they still damage the lymphatic system and the kidneys and alter the body's immune system. Because infection usually happens in childhood, visible effects may not appear until later in life.

When it becomes chronic it leads to lymphoedema (tissue swelling) or elephantiasis (thickening of skin and tissue) of the limbs and hydrocele (swelling of the scrotum). Involvement of the breasts and genital organs is common. The WHO says that such body changes often lead to social stigma, poor mental health and loss of income.

Acute episodes of local inflammation involving the skin, lymph nodes and lymphatic vessels often accompany chronic lymphoedema or elephantiasis. The WHO says some are caused by the immune response to the parasite, but most are the result of secondary bacterial skin infection where normal defences have been partially lost due to underlying lymphatic damage. These acute attacks are debilitating and may last for weeks.

NHS 111 Wales says filariasis is another infectious cause of lymphoedema, a common cause worldwide, but it is not generally a risk in the UK. In the UK, lymphoedema is far more often caused by other things. The NHS says primary lymphoedema is caused by faulty genes affecting the development of the lymphatic system, and secondary lymphoedema by damage to the lymphatic system or problems with fluid movement, which can be the result of cancer treatment, infection, injury, inflammation of the limb or lack of movement.

The practical relevance for UK residents is for people who have lived in or travelled for long periods to parts of the world where the disease is present, who develop unexplained swelling of a limb or the genitals. In that situation, tell your GP about your travel or residence history so it can be considered, because the cause is different from the more common UK explanations.

The NHS says to see a GP if you have the typical symptoms of lymphoedema, such as swelling in an arm or leg, and that in many cases it can be diagnosed from symptoms and medical history by examining and measuring the affected body part. You may be referred to a specialist lymphoedema treatment centre. Occasionally further tests are needed.

There is no cure for lymphoedema, but the NHS says it is usually possible to control the main symptoms using techniques to minimise fluid build-up and stimulate the flow of fluid through the lymphatic system, including wearing compression garments, taking good care of the skin, moving and exercising regularly, having a healthy diet and lifestyle, and specialised massage techniques.

Cellulitis, a bacterial infection of the deep layer of skin, is the most common complication of lymphoedema. The NHS lists redness and a feeling of heat in the skin, pain and increased swelling, and a high temperature or feeling hot, cold or shivery as symptoms. Antibiotics taken by mouth can usually treat it, although severe cases may need hospital treatment with antibiotics into a vein. Seek prompt medical advice if you suspect cellulitis.

The WHO says lymphatic filariasis can be eliminated by stopping the spread of infection through preventive chemotherapy, in which medicines are given annually to the entire at-risk population, an approach called mass drug administration. The medicines have a limited effect on adult parasites but reduce the density of microfilariae in the blood and prevent the spread of parasites to mosquitoes. Which combination is used depends on whether other filarial diseases are present in the region.

The WHO also describes a package of care for people living with the chronic effects: treatment for acute attacks, guidance in managing lymphoedema to prevent progression, surgery for hydrocele and treatment for infection. It says mosquito control, such as insecticide-treated nets and personal protection measures, is a supplemental strategy. It says that, as of 2023, 657 million people in 39 countries were living in areas that require preventive chemotherapy.

The NHS recognises that living with a long-term condition that affects appearance can cause distress and periods of depression, and advises talking to a GP or a member of the lymphoedema treatment team if you have been feeling down for the past few months. It points to the Lymphoedema Support Network for information, advice and support groups. The WHO makes the same point about the mental, social and financial effects of the disease.

Lymphoedema care in the UK is usually arranged through the NHS, either via a GP referral to a lymphoedema service or through a specialist unit. Suspected parasitic infection in a person who has lived abroad is typically assessed by an infectious diseases or tropical medicine clinic. Private consultations are an alternative route, and both should be given your full travel history.