Parasite in bathing lakes causes itching: 'Seems to be one of those years'

Swimmers across Sweden are reporting severe itching, a common ailment this summer attributed to a natural phenomenon: bird parasites in bathing lakes. These parasites, identified as cercariae, are the larval stage of flatworms that primarily inhabit waterfowl and freshwater snails. When conditions are favorable, they can penetrate the skin of swimmers, causing intensely itchy rashes.

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It is completely natural but is more noticeable in years with good swimming weather. It seems to be one of those years.

Stina Drakare, a researcher at the Swedish University of Agricultural Sciences (SLU), explains that cercariae are more noticeable in years with good swimming weather. "It seems to be one of those years," she stated. The parasites attempt to infect humans, mistaking them for birds, but cannot complete their life cycle as humans are the wrong hosts. The presence of snails and waterfowl in a lake can indicate a higher risk of encountering these parasites.

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They bite themselves and try to make humans their host, as if we were a bird.

Several locations in Sweden have reported cases, leading to temporary closures of swimming areas, such as the simskola in Glänninge sjö in Laholm. Municipalities like Alvesta have issued warnings for the Kojtet swimming spot. While the itching can be distressing, health authorities emphasize that it is not dangerous and usually resolves within a week. Drakare advises swimmers to shower and towel off vigorously after swimming and to change clothes to minimize the risk of infection. She also suggests seeking out clear, clean water for swimming.

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But they cannot. We are the wrong host for them.