[BEIJING] Scientists have identified a compound that could become a new treatment for schistosomiasis.
Publishing their study in Nature Medicine online last week (16 March), scientists from the US-based Illinois State University and the US National Institutes of Health used high-throughput screening — a method that rapidly tests large amounts of compounds for a particular activity — to identify compounds that target a schistosome parasite enzyme called TGR.
They tested the compounds on the TGR enzyme itself, the worms that carry schistosome parasites, and mice infected with Schistosoma masoni. The most effective compound killed worms at all the developmental stages and was effective against the three main schistosomes affecting humans.
Current schistosomiasis treatment relies largely on a drug called praziquantel (PZQ).
"Because PZQ is so inexpensive and effective, and has very low toxicity, the prospects and challenges for finding comparable new drugs are challenging," says David Williams, a professor of biological sciences at Illinois State University and one of the authors of the study.
But, "widespread reliance on PZQ for schistosomiasis control may hasten the selection of drug-resistant parasites," Williams told SciDev.Net, adding that this has increased the necessity to develop new pharmaceutical compounds against the parasite.
Xiao Shuhua, a professor from Shanghai-based National Institute for Parasitic Diseases under the Chinese Centre for Disease Control and Prevention, welcomes the study.
"PZQ does not kill the parasite larva. Therefore, schistosomiasis patients cured by PZQ can be re-infected. The repeated infection is one big application problem PZQ faces."
If a new compound with a different action mechanism is used in combination with PZQ, people can better control schistosomiasis and prevent resistance from developing, Xiao adds.
Separately, scientists from China, Thailand and the United Kingdom published a genetic analysis of Schistosoma mekongi — a species prevailing in the Mekong River in South-East Asian countries — in PLoS Neglected Tropical Diseases (19 March).
Schistosoma mekongi was thought to be prevalent only in the lower Mekong River and to have migrated southwards from China's Yunnan Province.
But the study shows that Schistosoma mekongi migrated from Vietnam to Laos, and that schistosoma epidemics in Mekong River are much more widespread than previously estimated.
"The human population at risk [of schistosomiasis in Mekong River] is up to ten times greater than originally estimated," write the authors.
Schistosomiasis is a parasitic disease infecting 200 million people throughout the tropics and subtropics and is responsible for 280,000 deaths annually.
Nature Medicine doi 10.1038/nm1737 (2008)
PLoS Neglected Tropical Diseases doi 10.1371/journal.pntd.0000200 (2008)