Deflating a Swelling Disease

The symptoms of filariasis are grotesque and difficult to ignore. Men develop a gross and painful swelling of the genitals. Women develop abnormally large breasts. Both sexes have limbs swollen to three times their normal size.

Victims also suffer socially. They are ostracized and often become despondent. Women often are rejected by their husbands or do not get married.

The parasitic disease, which often produces swollen body parts and is called elephantiasis, is transmitted by mosquitoes. But mosquito eradication efforts have failed to stem its spread.

New hope may be at hand. With a gift of more than 5 billion doses of an anti-parasite medication from a U.S. company, the World Health Organization is undertaking a massive campaign to eliminate lymphatic filariasis, a disease that affects at least 120 million people.

Recent studies have shown that albendazole, a SmithKline Beecham drug that is used widely to combat intestinal parasites, is more than 99% effective against the filariasis parasite when used with either diethylcarbamazine or ivermectin.

“We expect to see a dramatic decline in lymphatic filariasis within five or six years after the program gets underway,” said Jan Leschly, chief executive of SmithKline, which is donating more than $500 million worth of albendazole.

“This will be one of the largest global disease elimination programs ever undertaken by public health authorities,” said Dr. Hiroshi Nakajima, WHO director-general.

The incidence of filariasis is increasing in tropical and subtropical areas because of the rapid and unplanned growth of cities, which provide breeding sites for the mosquitoes that carry the disease.

About one-third of the 120 million victims live in India, a third in Africa and the remainder in Southeast Asia, the Pacific and the Americas. More than 1 billion people live in those areas and are at risk of infection.

Filariasis is caused by the threadlike worms Wucheria bancrofti and Brugia malayi, which live almost exclusively in humans. They lodge in the lymphatic system, the network of nodes and vessels that maintains the delicate fluid balance between the body’s tissues and blood. They produce millions of immature microfilariae or larvae that circulate in the blood.

Mosquitoes pick up the microfilariae when they bite humans. Over seven to 14 days, the microfilariae develop into the infective stage and migrate into the mosquito’s mouth, where they are transmitted to the people who are bitten.

Many victims go for years without outward signs of infection, even though their lymph nodes and blood are filled with the parasite. They may have unsuspected immune and kidney damage.

Diagnosing filariasis in such patients has been difficult until recently, so the true incidence of the disease is probably underestimated, experts say. In the past, the disease was diagnosed by drawing a blood sample and looking under the microscope for microfilariae.

But in many regions, the microfilariae are in the blood only at night, hiding out in capillaries in the lung during the daytime. Diagnostic tests thus had to be performed between 9 p.m. and 3 a.m.--inconveniencing both lab workers and patients. New techniques that look for parasite DNA or antibodies against the larvae have made diagnosis easier.

The worst symptoms generally appear in adults, and in men more often than women. In endemic areas, 10% to 50% of men suffer genital damage, including hydrocoele (a balloon-like enlargement of the sacs around the testes) and elephantiasis of the penis and scrotum. Elephantiasis of the entire leg, the arm, the vulva or the breast--swelling up to three times normal size--can affect up to 10% of men and women in these communities. Victims also suffer inflammation and bacterial infections.

The best current treatment is a single, yearly dose of either of the anti-parasite drugs diethylcarbamazine or ivermectin. One dose of either drug will kill 90% of worms and parasites for a year. But when albendazole is combined with either of these drugs, the efficiency is markedly increased: 99% of the microfilariae are killed and the worms are either killed or sterilized. This not only cures the patient, but also breaks the chain of transmission.

The treatment also has the advantage of killing a variety of other gastrointestinal parasites, including the hookworm, which is a severe problem in Africa.

“Previous studies have shown that if we treat intestinal parasites, children grow up bigger and stronger, and their ability to perform in school is enhanced,” said Dr. Eric Ottesen of WHO.

SmithKline Beecham sells about 50 million doses of albendazole yearly worldwide, said Brian Bagnall, who will manage the filariasis project for SmithKline. The drug has no significant side effects, he said.

SmithKline is undertaking the project, Bagnall added, because “we were looking for a major global project as part of our community outreach project, something that would affect a large number of people.”

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Parasitic Domain

Filariasis is endemic in tropical and subtropical regions of the world. About 375 million people will have to be treated in Africa, 660 million in Asia, 6 million in the Pacific Islands and 1 million in Central and South America.

Source: World Health Organization