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The Worm Turns on Parasite Treatment

Killing seizure-causing tapeworms better than leaving them alone

WEDNESDAY, Jan. 14, 2004 (HealthDayNews) -- Pork tapeworm infection is a leading cause of epileptic seizures in developing countries, and in some immigrants to the developed world as well.

What to do about the microbes has been a matter of considerable debate among disease-control experts, many of whom have feared that killing the worms in infected patients could worsen their symptoms by triggering inflammation in the brain.

Not so, says a new study that found wiping out the parasitic worms reduced seizures more than leaving them alone.

"Some people were saying that we should not be killing this parasite because it would do more harm than good," says study leader Dr. Hector Garcia, a worm expert at the Universidad Peruana Cayetano Heredia, in Lima, Peru. "We are doing more good than harm. People who receive the anti-parasitic treatment did better and it's very obvious that they didn't do worse."

A report on the findings appears in the Jan. 15 issue of the New England Journal of Medicine.

Pork tapeworm infection, or cysticercosis, is rampant in many parts of the world -- particularly in Latin America, where pig farming is common. Larvae of the organisms, which live in both pigs and humans and are called Taenia solium, are passed from person to person through contact with infested human feces. Worms travel to the brain, where they can cause small cysts that spark seizures.

Tapeworms also enter people via infected pig meat, where they dwell as larvae. The eggs mature into adults in the gut, and the adults shed more eggs into feces, perpetuating the transmission of the worms.

Drugs that kill the parasites have been available since the late 1970s, but not all doctors have embraced them. Opponents of the treatment argue that many of the cysts disappear on their own over time and drug therapy may lead to permanent seizures by damaging the brain. Advocates of the treatment claim that eradicating the worms prevents seizures from recurring and makes managing the cysts easier.

To test this question, Garcia and his colleagues gave a combination of the worm-killing drug albendazole and the powerful anti-inflammatory drug prednisone to 60 men and women with worm-induced seizures. They gave sugar pills to 60 others with the condition. Patients were watched for 30 months, or until they'd been free of seizures for at least six months.

The rate of partial seizures -- attacks on one side of the brain -- were the same in each group. However, patients who received albendazole had a 63 percent reduction in their chances of suffering "generalized" seizures across their whole brain. What's more, treatment with the drug increased the odds that cysts would heal compared with doing nothing, the study found.

Of the 75 million people in Latin America at risk of the disease, 10 percent develop symptoms, says study co-author Dr. Robert Gilman, a researcher at the Johns Hopkins University Bloomberg School of Public Health.

To best prevent cysticercosis, countries need to make pig husbandry cleaner, Gilman says. Economic development is a proven remedy, eradicating the disease in the United States and other industrialized nations. But development hasn't been quick enough elsewhere.

Although albendazole is often subsidized, Gilman says the therapy isn't meant for widespread control of worm infection: "You're not treating everybody, only those with seizures."

But Dr. James Maguire, chief of parasitic diseases at the U.S. Centers for Disease Control and Prevention, says the bigger costs of treating cysticercosis involve diagnosing the condition, which requires sophisticated brain scans. "It's the unfortunate reality of a lot of modern medicine. Poor people don't have access to it because of the cost," says Maguire, author of a commentary on the journal article.

Tapeworms are vulnerable at various points in their lifecycle, Maguire says. Adult worms can be safely destroyed in humans and pigs with drugs, and a porcine vaccine is, in theory, possible. However, none has yet been developed, he says.

More information

For more on cysticercosis, try the Centers for Disease Control and Prevention. For more on tapeworms, visit the U.S. Department of Agriculture.

SOURCES: Hector Garcia, M.D., Ph.D., associate professor, Universidad Peruana Cayetano Heredia, Lima, Peru; Robert Gilman, M.D., professor, international health, Johns Hopkins University Bloomberg School of Public Health, Baltimore; James Maguire, M.D., chief, parasitic diseases branch, U.S. Centers for Disease Control and Prevention, Atlanta; Jan. 15, 2004, New England Journal of Medicine
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