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Exploring the cost-effectiveness of treating parasitic-worm diseases

A group of tiny worms are the source of great distress - and sometimes death - for a staggering 1.5 billion people in the developing world. Yet a small percent of affected people are treated for these ailments, which include helminth infections, such as hookworm, roundworm and whipworm, and schistosomiasis.

The offending worms, found in soil and water, can latch onto people while they walk barefoot in contaminated soil or bathe in infested lakes and streams. The parasitic worms then slither their way into the intestine or into the blood vessels around the intestines or bladder, where they cause great discomfort and disease.

Children commonly develop anemia and stunted growth and cognitive problems. Adults may also have abdominal discomfort and pain, wasting and sometimes more serious complications, such as a bowel or bladder obstruction or renal failure, which can be deadly.

WHO guidelines mostly target school-aged children for treatment, which costs pennies to administer, because children are heavily affected and are easily treated as they congregate in schools, says Stanford’s Nathan Lo, author of a new study on treatment of these parasitic worm diseases. The study, which appears online in Lancet Global Health, shows that treating an entire community, including adults, reaches many more people and is highly cost-effective.

Lo, a third-year Stanford medical student and research associate, said he decided to do the study after he realized the WHO guidelines hadn’t changed for decades and had never been rigorously analyzed. He and his colleagues modelled patterns of these diseases in four different communities in the Ivory Coast to see whether it was worthwhile and cost-effective to expand drug treatment, which is cheap and readily available. The drug albendazole costs about 3 cents and a pill and significantly reduces the number of worm eggs from the soil-transmitted helminths, while praziquantel costs 21 cents a pill and effectively reduces egg production in cases of schistosomiasis, he said.

“Most of the money spent on treating these diseases is focused on helping kids,” Lo told me. “But there are a lot of symptoms of disability in adults as well, and our results support the expansion of treatment to this adult population.”

Moreover, he noted, “If you only treat children, it might help them, but they often come home to neighbors, parents and teachers who may be infected, and the children can once again become infected. It’s more effective for children if you treat them and the people around them.”

In fact, the researchers’ findings show that community-wide treatment is highly cost-effective, even if it’s assumed that costs are 10 times what the researchers assumed. They also found that it’s worth the investment to treat people more frequently – at six-month intervals – and to do the drug treatments together, rather than as separate programs.

Given the findings, the scientists strongly urge the WHO to re-evaluate its guidelines to expand treatment to communities as a whole.

Photo of hookworms from Wikipedia

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