It remains undetected for years and has flourished unchecked for many more. It is also known to cause unimaginable - and completely avoidable - pain and problems. Lymphatic Filariasis is a disease caused by parasitic worms, which can live, unnoticed in human bodies for over a decade.  Over the years, Filariasis has placed at risk at least one billion people the world over - one out of every six people alive.

The worst part is that many people do not even know that they have been infected until it is too late. Upon manifestation, Filariasis results in a grotesque swelling of limbs and that is the reason why the disease is also called Elephantiasis or the Malabar Leg.

The parasite has a life span ranging between four to six years and during this time, it releases millions of microfilariae into the blood. A person who has these microfilariae is called a 'silent' carrier, who plays host to the filarial worm. Mosquitoes transmit this disease from a silent carrier to another person. Although rarely fatal, Filariasis is debilitating and disfiguring and the patient has to endure considerable pain. While 25 million men suffer from genital disease (one of the possible outcomes), a majority of the 15 million, who have elephantiasis of the leg, are women.

With approximately 120 million people in tropical and subtropical areas of the world affected by this disease, the World Health Assembly in 1997 adopted a resolution for the elimination of Lymphatic Filariasis as a global health problem.

The World Health Organization (WHO) lists 80 countries in Africa, America, Eastern Mediterranean, South Asia, South-East Asia and the Western Pacific region as endemic. Seventy per cent of the total infected cases are reported from India, Nigeria, Bangladesh and Indonesia.

In 1999, two years after the World Health Assembly adopted a resolution for the elimination of the disease, 10 countries initiated small-scale national program activities; and a year later the program was extended to cover 15 per cent of the global infected population. It is estimated that by the end of this year, the program activities will be extended to 25 per cent of the infected population.

As part of the worldwide Filariasis elimination program, a pilot project was initiated in the southern Indian state of Tamil Nadu in March this year. A mass drug administration program for the elimination of Lymphatic Filariasis has just been concluded in 13 endemic districts of the state. More than 120,000 volunteers administered the anti-parasite drugs to over 28 million persons in the program, jointly organized by the Department of Public Health and Preventive Medicine, Tamil Nadu, and the Vector Research Centre, Pondicherry, in association with the World Health Organization.

Says P Krishnamurthy, Director of Public Health and Preventive Medicine, the department spearheading the project in Tamil Nadu, "This was a pilot project conducted on an unprecedented scale. The challenges were many and so, we hope, will be the rewards."

This pilot project is the first step towards the total elimination of the disease over the next five years. The National Program to Eliminate Filariasis has two chief goals. Firstly, it aims to interrupt transmission of infection and secondly to alleviate and prevent both the suffering and disability caused by the disease.

Says Anuradha Kathi Rajivan, an IAS officer and Project Coordinator of the Integrated Child Development Services (ICDS) which is playing an instrumental role in the elimination program, "At the point where visible manifestation has already set in, cure is not possible. Only a certain degree of comfort can be provided to the victim. This is why prevention is very important. The chain of transmission has to be broken. That is the key to total elimination."

According to WHO, a once-yearly treatment, preferably with two drugs together, for a period of four to six years with good compliance of the affected population, can guarantee elimination of the disease. The anti-parasite drugs Diethylcarbamazine (DEC) and Albendazole, earlier thought to be of use only to patients battling full-fledged symptoms, were discovered to display extraordinary efficacy in preventing its occurrence in world trials less than a decade ago. They are the focal weapons in WHO's thrust towards global elimination of Filariasis by the year 2020.

Convincing people to take the drug, however, is a major cause of concern for the administration in Tamil Nadu. Hence, a large part of the groundwork before the pilot project took off involved training volunteers to 'market' the need of taking the medicines. The volunteers, who moved from house to house, were also required to ensure that the medicines were consumed in their presence.

The pilot project targeted the entire population in the identified endemic districts. To interrupt the transmission, everyone was considered "at risk" and administered the dose on a particular day. Experts say that this drug helps to destroy the worm and reduces the number of parasites to a level below which the mosquito vector can no longer transmit infection.

This project, which was partially funded by the Bill Gates Program through WHO, hopes to move to other endemic coastal states - stretching from Orissa in the East to Gujarat in the West.

Experts also maintain that poverty is both a cause and a consequence of the disease. Those living in overcrowded areas with larger mosquito populations are more vulnerable. Once afflicted, disability, disfigurement and ostracism follow, dealing a double blow to the already disadvantaged. It also prevents a person from having a normal working life and destroys social ties.

The incidence of disease cuts across both genders though women are more likely to suffer the consequences of social ostracism. At the first and second stage, with early swelling, the disease is still reversible. But, says Dr Agastyan, Joint Director of the project's nodal body, "Visible manifestation, even in the preliminary stages, ruins the marriage prospects of a woman in rural and orthodox societies. Filariasis is not transmitted conjugally although those who share the same environment are likely to turn carriers." So a fight against Filariasis is also a fight against poverty and social discrimination.

Lymphatic Filariasis also imposes an enormous burden on medical infrastructure in the endemic areas. In India alone, health costs for Filariasis are estimated to be in excess of $1.5 billion annually. At the same time, in India, where one-third of the cases occur, seven to eight per cent of the male labour in some communities are victims of the chronic disease.

And yet, an independent International Task Force for Disease Eradication identified Lymphatic Filariasis as one of the six infectious diseases it considered "eradicable" or "potentially eradicable". According to estimates, Filariasis can be eliminated for as little as US $1 per person for a four to five year program. This is backed by the fact that China, Japan and Taiwan have managed to eradicate Filariasis completely.

It is hoped that Tamil Nadu's pilot project is the beginning of the end for Filariasis in India.