Antiparasite Triple Play

23 January 2008 (All day)

Albis Gabrielli

War on worms.
Giving three drugs at once allows health workers in Zanzibar to cure more people of their parasite infestations.

One of the world's best health care bargains just got better. A new study conducted in Zanzibar, Tanzania, shows that three drugs can safely and simultaneously treat three of the world's most burdensome parasites. The medicines are cheap--pennies per person--but delivering them to patients isn't. Until now, no one was sure if health workers could safely economize by giving all three at once.

Parasitic worms infect more than a billion people in tropical and subtropical regions. Helminthiasis, filariasis, and schistosomiasis result from worms that live in the intestines, lymphatic system, and bloodstream, respectively. The same person often suffers from all three diseases, which can cause developmental delays, anemia, malnutrition, liver and kidney damage, and long-term disability.

The worms are easily thwarted by so-called preventive chemotherapy: a single annual dose of the drugs ivermectin, albendazole, and praziquantel. What's more, drug companies donate ivermectin and albendazole, and generic praziquantel costs eight cents per dose. Delivery is the problem. People currently take ivermectin and albendazole together for filariasis and helminthiasis and praziquantel separately for schistosomiasis. They often obtain the drugs from different programs that target the different diseases, but even when all three are available, clinicians administer only one or two at a time to avoid possible side effects. If health workers could give all three drugs at once without side effects, they could reach 30% more people without increasing their budget, says David Molyneux, a parasitologist at the Liverpool School of Tropical Medicine in the U.K. "You just don't know until you try," he says.

So Molyneux worked with an international team of researchers and the government of Zanzibar to launch the first large-scale safety study of all three drugs. After a successful preliminary trial with 5000 adults and children, researchers extended treatment to everyone in Zanzibar, training health care workers and advertising through community leaders and mass media. Ultimately, more than 700,000 people swallowed all three pills. Only 1.4% of them reported any side effects, the researchers report online today in PLoS Neglected Tropical Diseases. "There was a little nausea, vomiting, and headache," Molyneux says, "but no one went to the hospital, and no one stopped work." Still, he says that many people in Zanzibar were not heavily parasitized. The more worms that die, the worse the side effects--so severely infected people should first take the drugs individually.

"This was a much-needed study," says Peter Hotez, a medical parasitologist at George Washington University in Washington, D.C. He's not surprised that the three drugs are safe together, but proving it "provides the scientific foundation for one of the most cost-effective measures in all of public health." He and the authors call for an expanded program of triple-drug administration to treat millions of people in affected regions.

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