Snails n’ schistosomiasis: Shelled slugs in U of A laboratory could be the answer to solving the ‘swimmer’s itch’

Though the snails kept in Patrick Hanington’s lab at the School of Public Health may look harmless, they play an integral part in understanding one of the world’s most widespread diseases.

Hanington and his team study schistosomes, a type of flatworm. These diseases spread by these aquatic snails range in severity, from the simple mosquito bite-like bumps of swimmer’s itch to the liver failure-causing schistosomiasis.
The snails, which make up one step on the parasite’s life cycle and are essential to its survival, may hold the answer to mitigating the spread of the disease.

“There’s a lot of people who work on the human side of the disease and immunology,” Hanington said. “But we don’t know how the snails deal with the infection.

“There have been a couple pretty big studies that show if you don’t have a meaningful control approach with the snails, you’ll never have a significant impact on the disease.”

Hanington’s lab runs two projects simultaneously which study the schistosome worms to better understand their biology. The first of these projects deals with the swimmer’s itch worm commonly found in Alberta lakes.

Comprised of two parts, this project combines a website where people can report cases of the itch and get information as to where others have been infected. One of the graduate students working in the lab also travels around the Edmonton area on a weekly basis, collecting samples of the snails. This allows the lab to see which parasites are infecting the snails and how far they are along the life cycle.

The goal of the online portion of the project is to allow users of the site to make informed choices about where and when they swim.

The parasites that cause swimmer’s itch only make it into the skin of the humans they infect. This causes an immune reaction and the annoying red bumps any lake-swimmer is familiar with. Schistosomiasis-causing worms, meanwhile, get into the bloodstream of humans, which can cause profound health issues, such as liver failure and kidney problems.

“Schistosomiasis infects around 250-million people worldwide,” Hanington said. “It’s often considered the second most important disease in terms of public health next to malaria.”

Since the schistosome is a free-swimming parasite, victims do not have to come in contact with a host to be infected. This, and the waterborne nature of the flatworm, mean that children are infected most often after playing in the water.

Schistosomiasis often affects large portions of the human population in South America, Asia and Africa. Lower socio-economic status and limited health care access important hurdles when dealing with schistosomiasis.

“We have a lower burden of worm infections (in North America),” Hanington said.

Though they are one of only three labs worldwide currently studying swimmer’s itch, Hanington said he hopes his research can have a real impact on the understanding of schistomsome biology.

“You can’t just shut your doors and expect ‘tropical’ diseases not to affect you in some way,” he said.

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