Fig.1. Adult male and female Schistosoma parasite worms. The female is thinner and fits within the male (Photo courtesy of David Rollinson, NHM)
With almost 240 million people infected in more than 70 countries, schistosomiasis is second only to malaria in common parasitic diseases. Unlike malaria, this disease is a member of the Neglected Tropical Diseases (NTDs), which are too often overlooked in public awareness and funding. One collection, however, acts as a repository to ongoing schistosomiasis research around the world.
The Schistosomiasis Collection at the Natural History Museum in London (SCAN) is an essential resource for studying the disease’s parasitic flatworm, known as a schistosome, and its snail hosts. These parasites begin life as free-swimming larvae, which infect freshwater snails before transferring to humans. Once inside the human body, the schistosomes mature to adults and release eggs that ultimately cause the painful and sometimes fatal disease. Eggs may be released back into the water to start the life-cycle anew. Despite the parasite’s small size and complicated life-cycle, infection is prevalent in the tropics and subtropics, with the vast majority of cases occurring in children in Africa.
Collecting with a purposeInitially, scientists at the Natural History Museum, London (NHM) focused on the interactions between the parasites and their hosts. With the advent of newer technologies and the ability to focus on DNA, they made some changes. Dr. David Rollinson and Dr. Aidan Emery, NHM parasitology researchers involved with SCAN, saw significant potential for a new type of research-based collection. This collection would connect traditional biodiversity and morphological studies with public health efforts around the world.
“It became clear that some of our collections weren’t quite as good as they should be. We needed to grow the collections. We needed to make them more comprehensive,” Rollinson explained. “So SCAN came about because of that need.”
Over the past few years, they have collected more than 200,000 individual schistosome larvae, later-stage parasites, and snail hosts from different countries. Although this number seems large, these parasites are a precious commodity within the research community. When parasites spend part of their lives in human and snail vessels, the amount of material is extremely limiting. Luckily, molecular techniques, like whole genome amplification, make the collection more accessible and allow scientists to compare both the morphology and genetics of specimens.
Onward and upwardAt the moment, SCAN is focused on training people in endemic areas who can collect and expand their repository. Unfortunately, collecting and transporting parasites across country borders is very difficult. Travel to some locations may be impossible.
“For instance, we can’t at the moment travel to some of the countries we’d like to in Africa because of the political situation,” Emery said.
Despite these limitations, Rollinson and Emery are hopeful. With the help of two other staff members at NHM, they want to continue with their success as a resource for medical and biodiversity research. Initiatives such as the Schistosomiasis Control Initiative (SCI) and the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) depend upon the repository’s specimens for ongoing research and drug administration.
These groups, as well as the World Health Organization, connect SCAN to efforts in sub-Saharan Africa to mitigate the disease. SCAN is ultimately a multidisciplinary operation, from studying the ecology of the parasite to addressing public health. Eventually Rollinson and Emery would like to expand the collection content to encompass other infected countries, such as India, and even other parasitic diseases. For now, they are utilizing recent advances in molecular biology to compare older specimens to ongoing outbreaks.
“The message there is that some of the old parasite and snail collections are of value and can now be studied using exciting modern, molecular approaches,” Rollinson said.
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Schistosomiasis: A major public health problem. (n.d.). WHO online. Retrieved from http://www.who.int/schistosomiasis/en/.
What is Schistosomiasis? (n.d.). Natural History Museum, London. Retrieved from http://www.nhm.ac.uk/research-curation/life-sciences/parasites-vectors/research/human-disease/schistosomiasis-research/about-schistosomiasis/index.html.