Lymphatic Filariasis (LF), also known as elephantiasis, is a severely disfiguring disease which affects 120m around the world.
It can be treated, but the drugs are not always available to those most at need.
What are the symptoms?
The condition is associated with huge and disfiguring enlargement of a limb, or areas of the trunk or head. These swellings are known technically as lymphoedema.
In addition, the skin usually develops a thickened, pebbly appearance and may become ulcerated and darkened.
Other symptoms can include fever, chills and a general feeling of ill health.
The disease may also affect the sexual organs. In a man, the scrotum may become enlarged, and the penis may be retracted under the skin.
In women the external genitalia may be covered in a tumourous mass.
People with the condition often have to contend with social as well as physical problems.
Communities frequently shun women and men disfigured by the disease.
Many women with visible signs of the disease will never marry, or their spouses and families will reject them.
They are also frequently are unable to work because of their disability.
What causes it?
It is caused by microscopic, thread-like parasitic worms invading the body's lymphatic system - the network of vessels carrying infection-fighting cells.
The worm is spread by mosquitoes, who pass it on when they take blood from humans.
The bacteria-containing worms lodge in the lymphatic system, producing millions of minute larvae which spread throughout the bloodstream.
These worms disrupt the balance of the lymphatic system, which helps maintain the fluid balance between the tissues and the blood.
What is still not clear is how much this is down to the worms causing obstruction of the lymphatic vessels, or the immune response their presence triggers in the body.
However, once the tissues have been damaged, they also become vulnerable to other bacterial and fungal infections, which are often responsible for much of the disease seen in LF patients.
Recent studies have also suggested that the disease may be caused by the red soil on which certain barefooted populations live.
It is believed that small chemical particles found in the soil may enter the skin through the bare feet, lodging in the lymphatic tissues and producing irritation which increases the vulnerability to bacterial infection.
Who is most at risk?
Over 120 million have already been affected by it, over 40 million of them are seriously incapacitated and disfigured by the disease.
One-third of the people infected with the disease live in India, one third are in Africa and most of the remainder are in South Asia, the Pacific and the Americas.
In communities where the condition is endemic, 10-50% of men and up to 10% of women can be affected.
Though the infection is generally acquired early in childhood, the disease may take years to manifest itself.
How is it treated?
Drugs such as albendazole and diethylcarbamazine (DEC) have been shown to be effective in killing the parasites.
Their use not only eases symptoms, particularly among people in the early stages of disease, but also prevents the parasites being spread to others in the community.
A study in the Lancet, published in 2005, found that doxycycline, a widely available antibiotic, is also highly effective at killing the parasites.
Careful cleansing can also have a significant impact, helping to heal infected areas, and reversing some of the tissue damage, particularly that associated with secondary bacterial or fungal infections.
Measures to improve the flow of the lymphatic fluid, such as raising and exercising the swollen body part can also help.
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