Invisible Water Parasite Causes Itching for Swedish Swimmers

Swimmers in Sweden are facing a new nuisance in addition to algae blooms and sewage concerns: an "invisible water parasite." Reports have emerged of swimmers at Långholmen beach experiencing "unbearable" itching after encountering cercariae, a parasite commonly found on water birds. While the cercariae are harmless to humans, they can cause significant discomfort when they attach to skin during a swim.

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If you swim just when there is such a period, then I think it attacks everyone who is in the water.

Stina Drakare, a researcher at the Swedish University of Agricultural Sciences (SLU), confirmed that while the parasite is harmless, it can cause bothersome itching. She noted that if the parasite is present in the water during a specific phase of its life cycle, it can affect anyone swimming at that time. Drakare stated that outbreaks are not uncommon in Swedish lakes and inland waters, including the Uppland region where she is based.

The issue adds to existing concerns about water quality in Swedish lakes, particularly Mälaren. Recent reports have highlighted sewage discharges and harmful algae blooms affecting various swimming spots. Drakare suggests that choosing smaller lakes, especially those surrounded by forests rather than agricultural land, might offer a better swimming experience, as they are less likely to be impacted by sewage and agricultural runoff.

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In Uppland, where I am, it absolutely occurs.

Preventing contact with cercariae is difficult as they are microscopic and not weather-dependent. Drakare recommends showering immediately after swimming, regardless of water conditions, as the fresh water can help prevent bacteria from causing further issues. She also noted that while large lakes like Mälaren were worse in the 1960s due to agricultural fertilization and household plumbing, current trends can reverse, emphasizing the need for ongoing monitoring and informed choices for swimmers.

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Sometimes it is better to go to a small lake, which is not a plain lake... surrounded by forest, like Mälaren is, for example. Because in a forest lake in the same area, there is often not the same impact from sewage and agriculture.