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The Debate Is On: To Deworm Or Not To Deworm?

A girl cries while receiving a deworming pill in Managua, part of a campaign by the Nicaraguan Ministry of Health.

To deworm or not to deworm, that is the question.

Actually, it's a surprising question. You'd think that it'd be a good idea to treat all children with deworming drugs in parts of the world where intestinal worms are a problem.

More than 2 billion people in some of the poorest areas of the world are infected with intestinal worms. These worms — hookworm, roundworm and whipworm — have been around for centuries. They lay eggs in human intestines; when excreted, the worms and their eggs can be spread to others. In those infected, the worms cause intestinal blood loss leading to iron deficiency and malnutrition — and loss of energy and motivation.

But a report published by the Cochrane Review in July on deworming sparked some controversy.

The report concluded that routine deworming of all children in areas with high rates of infection — whether they're shown to have intestinal worms or not — is not, on average, beneficial to the kids.

The finding contradicts the current recommendation by the World Health Organization to periodically treat all children and women of childbearing age with deworming drugs in areas where large numbers of people are affected, including parts of sub-Saharan Africa, India, China, East Asia and the Americas.

Observational studies — studies that attempt to understand cause and effect by observing large groups of people — have provided evidence that mass deworming treatment has benefits.

"There's evidence that children treated with deworming medication grow better and have better cognitive performance," says Judd Walson, associate professor at the University of Washington. Walson wrote an editorial in the Oct. 22 issue of PLOS: Neglected Tropical Diseases. "A study from Kenya showed better school performance and even better job performance."

But the Cochrane Review, which summarizes evidence from existing research, didn't look at observational studies. Typically, Cochrane reviewers look only at clinical trials, considered the gold standard of science because researchers can control how subjects are assigned to different experimental groups and which treatment each group receives.

"They're saying that there's a lack of evidence of benefit, not that there's evidence of a lack of benefit. And that's a critical distinction," Walson says.

After the Cochrane Review piece, three other papers were published in PLOS: Neglected Tropical Diseases, each taking issue with the Cochrane Review's conclusion, and expressing concern that by looking at only one type of evidence, health policy experts might conclude that mass deworming is a futile exercise. (You can read the papers here, here and here.)

"Not only is such a review of little value in guiding global deworming policy, it could also generate confusion among public health planners and practitioners," wrote the authors of one paper.

A century ago, research funded by millionaire John D. Rockefeller — who had wanted to expand his industrial holdings in the South but found a lethargic workforce — helped move treatment of intestinal worms forward. At the time, a public health campaign began to get people to install sanitary outhouses that buried waste more than 4 feet deep (the worms can crawl up to four feet through soil); wash their hands, so people touching worms or their eggs don't ingest them; and avoid walking barefoot because the tiny worms can make their way through pores in the feet.

Ridding the developing world of intestinal worms would take a similar commitment. But testing and then treating individuals known to have intestinal worms is costly and can be impossible in some regions of the world that lack laboratory equipment and trained technicians. And outhouses in some regions of the world are of poor sanitary quality or non-existent. Until such facilities are more widely available, it's cheaper to treat everyone, infected or not, in areas where there is a major problem with worm infection.

"Children in the poorest communities of the world should not have to live with worms," Walson says. "We should be deworming the kids. It's very low cost and has essentially no side effects."

It's clear from the flurry of papers published reacting to the Cochrane Review that many in the field of tropical disease agree with Watson. What the Cochrane Review uncovered was a lack of solid scientific evidence to support a program that many public health advocates believe is valuable. And that, says Walson, presents an opportunity to do the kind of study that would shed important light on the question of whether to treat all children in affected areas with deworming drugs: a study of tens of thousands of people in different geographic regions testing mass deworming against other interventions.

"There's a real commitment from the global community to make it happen," he says. That commitment became real on November 5 when the Bill and Melinda Gates Foundation awarded a grant to the Natural History Museum in London, with Walson as the principal investigator, to fund clinical trials through 2020 in several countries in Africa and South Asia. (The Gates Foundation is also a funder of NPR's global health coverage.)

The details of funding or the specific countries are not yet available, but the trials represent the goal standard of science that should, finally, provide evidence on the value of deworming all vulnerable children.

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