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A new framework for expanding treatment guidelines for parasitic worm diseases

Schistosomiasis outbreakA new health economics evaluation unveiled last week shows historical World Health Organization treatment guidelines for the two most common parasitic worm diseases are far too restrictive, and it provides a framework for the necessary expansion of global treatment programs.

The findings were presented by Nathan Lo, a third-year Stanford medical student, at the American Society of Tropical Medicine and Hygiene Annual Meeting in Philadelphia, which convened infectious disease experts from around the world to share the latest scientific advances in tropical medicine and global health.

These diseases - schistosomiasis and soil-transmitted helminthiasis - are caused by tiny worms found in water and soil that can cause severe discomfort and even death after coming into contact with humans. Together, they infect some 1.5 billion people in the developing world.

The medications to treat these diseases are cheap and highly effective, but there's a large unmet need in treatment. Under the current WHO guidelines, treatment is focused upon school-aged children living in high prevalence areas. These guidelines have been largely unchanged for nearly a decade and leave many infected people untreated.

“The prevalence thresholds that have defined mass drug administration for nearly a decade were developed based upon expert opinion, but they are not based on rigorous scientific evidence,” said Lo. “We are urging the WHO to consider lowering the current thresholds and expanding global treatment programs.”

Stanford's Jason Andrews, MD, the senior author of the study, Lo and colleagues have proposed a new framework for determining the optimal treatment strategy – who to treat, how often, and with what medicines – based on prevalence thresholds in a specific community using economic modeling. The findings show that expanding mass drug administration in communities with much lower disease prevalence would not only be cost-effective, but would result in improved quality of life, reduce re-infection rates and lower disease intensity. If adopted, this would result in a five-fold increase in the number of people who would receive treatment in sub-Saharan Africa alone.

For example, in the case of schistosomiasis, current guidelines say to wait until one in every two children is infected (50 percent prevalence) before providing treatment. However, the study found treating children in communities with as little as a 5 percent schistosomiasis prevalence would actually be cost-effective.

Expanding treatment to the entire community would also be cost-effective in areas where the community prevalence is 20% for schistosomiasis and 65% for soil-transmitted helminthiasis, but current guidelines do not recommend treating the entire community at any prevalence. Treating adults could significantly reduce transmission rates and reduce disability in both adults and children, said Lo.

The results also provide support for integrating mass drug administration efforts to include multiple medications in the treatment of parasitic worm diseases since the majority of cost is from delivery of treatment and co-infection is common.

I had a chance to speak with Lo after his presentation at ASTMH; watch this brief video interview to learn more. Lo and Andrews were among several Stanford researchers who presented their work at the meeting; the Center for Innovation in Global Health website offers more updates, photos and videos from ASTMH.

Rachel Leslie is the communications officer at Stanford’s Center for Innovation in Global Health.

Previously: Exploring the cost-effectiveness of treating parasitic-worm diseases
Photo, of an investigation of a 2012 schistosomiasis outbreak in Zimbabwe, by CDC Global

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