Research shows parasite more dangerous than thought

Watch out, schistosomiasis warriors. Brown researchers have found you're in for more of a challenge than previously thought.

A study published March 5 by a Brown professor and an alum shows the parasitic infection's effect on global health is more significant than was known.

A team of researchers led by Julia Finkelstein '05, now a graduate student in nutritional anthropology at the Harvard School of Public Health, evaluated field research conducted in the Philippines by Stephen McGarvey, professor of community health and anthropology. They found that the disease burden of the parasite Schistosoma japonicum is "seven to 46 times greater than current global estimates" made by the World Health Organization's Global Burden of Disease Project, a University statement said.

"Disease burden is composed of the number of years lost because of early death or disability," Finkelstein said. The previous estimates did not fully account for the level of disability caused by this disease and thus underestimated its impact on global health, she said.

Schistosomiasis infects over 200 million people, mostly in developing nations, according to the release. It is caused by five species of flatworms, said Helene Carabin, associate professor of biostatistics and epidemiology at the University of Oklahoma Health Sciences Center and epidemiology specialist on the research team. The parasites, spread by snails, typically enter the body through the skin when people use water containing the flatworms, Carabin said. The parasites often attach near the digestive system as they take nutrition from the host, causing diarrhea, intestinal bleeding, anemia, enlarged spleen, organ damage and, in rare cases, brain damage, Carabin added.

The original research goes back to 1999, he said. McGarvey "had been working in the Philippines on that worm for several years," Carabin said. After seeing a proposal from the NIH seeking research into the ecology of infectious diseases, McGarvey decided to apply for a grant, Carabin said.

McGarvey could not be reached for comment.

One particular strain, called japonicum, can cause brain infection at slightly higher rates than other strains, but "what's special about japonicum, unlike the other strains, is that it can infect a very large number of mammals," Carabin said. As a result, unlike the other Schistosoma parasites, eradication of the disease cannot be achieved by simply treating humans and snails.

"Even if you treat humans and say humans can be infected by the strain which affects dogs, you'd also need to take care of the dogs," Carabin said. "In terms of the ecology, it's very, very complex. It also has a snail in its life cycle, so when you put all these animals and the snail (together), it makes it a very interesting ecological model. So that's why we decided to apply to that grant."

The results of his team's study may support greater funding for studying and treating schistosomiasis, according to Mark Schleinitz, assistant professor of medicine and a member of the research team. "We also point out that our methods might be useful in assessing the overall morbidity of other multi-system infections," he wrote in an e-mail.

"I'm hopeful that our findings will help inform more accurate assessments of disease burden of schistosomiasis and more broadly for infectious disease," Finkelstein said. "We're hoping our finding will help drive the global agenda for schistosomiasis and infectious diseases worldwide."