National Filaria Day 10th Nov

What is Lymphatic Filariasis?

Lymphatic Filariasis, known as Elephantiasis, puts at risk more than a billion people in more than 80 countries. Over 120 million have already been affected by it and 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 rest are in South Asia, the Pacific and the Americas. In tropical and subtropical areas where lymphatic filariasis is well-established, the prevalence of infection is continuing to increase. A primary cause of this increase is the rapid and unplanned growth of cities, which creates numerous breeding sites for the mosquitoes that transmit the disease.
In its most obvious manifestations, lymphatic filariasis causes enlargement of the entire leg or arm, the genitals, vulva and breasts. In endemic communities, 10-50% of men and up to 10% of women can be affected. The psychological and social stigma associated with the disease is immense. In addition, even more common than the overt abnormalities is hidden, internal damage to the kidneys and lymphatic system caused by the filariae.

The thread-like, parasitic filarial worms Wuchereria bancrofti and Brugia malayi that cause lymphatic filariasis live almost exclusively in humans. These worms lodge in the lymphatic system, the network of nodes and vessels that maintain the delicate fluid balance between the tissues and blood and are an essential component for the body's immune defence system. They live for 4-6 years, producing millions of immature microfilariae (minute larvae) that circulate in the blood.

The disease is transmitted by mosquitoes that bite infected humans and pick up the microfilariae that develop, inside the mosquito, into the infective stage in a process that usually takes 7-21 days. The larvae then migrate to the mosquitoes' biting mouth-parts, ready to enter the punctured skin following the mosquito bite, thus completing the cycle.

What are the symptoms?

Though the infection is generally acquired early in childhood, the disease may take years to manifest itself. Many people never acquire outward clinical manifestations of their infections. Even though there may be no clinical symptoms, studies have now disclosed that such victims, outwardly healthy, actually have hidden lymphatic pathology and kidney damage as well. The asymptomatic form of infection is most often characterised by the presence in the blood of thousands or millions of larval parasites (microfilariae) and adult worms located in the lymphatic system.

The worst symptoms of the chronic disease generally appear in adults, and in men more often than in women. In endemic communities, some 10-50% of men suffer from genital damage, especially hydrocoele (fluid-filled balloon-like enlargement of the sacs around the testes) and elephantiasis of the penis and scrotum. Elephantiasis of the entire leg, the entire arm, the vulva, or the breast - swelling up to several times normal size - can affect up to 10% of men and women in these communities.

Acute episodes of local inflammation involving skin, lymph nodes and lymphatic vessels often accompany the chronic lymphoedema or elephantiasis. Some of these are caused by the body's immune response to the parasite, but most are the result of bacterial infection of skin where normal defences have been partially lost due to underlying lymphatic damage. Careful cleansing can be extremely helpful in healing the infected surface areas and in both slowing and, even more remarkably, reversing much of the overt damage that has occurred already.

What is the treatment?

The primary goal of treating the affected community is to eliminate microfilariae from the blood of infected individuals so that transmission of the infection by the mosquito can be interrupted. Studies have shown that single doses of DEC have the same long-term effect in decreasing microfilaraemia as the formerly-recommended 12-day regimens of DEC and, even more importantly, that the use of single doses of 2 drugs administered concurrently is 99% effective in removing microfilariae from the blood for a full year after treatment. It is this level of treatment effectiveness that has made feasible the new efforts to eliminate lymphatic filariasis.