Invisible water parasite affects Swedish bathers

A microscopic bird parasite is causing severe itching for swimmers across Sweden, with reports of children in distress after bathing in affected waters, according to a report by public broadcaster SVT.

Karin Åsblom from Borlänge told SVT her family developed hundreds of itchy spots after swimming in Gränna. Her children’s reactions were extreme: “My daughter screamed that she wanted to die, and my son said he wanted to be in a coma.”

The condition, known as swimmer’s itch, is caused by cercariae—parasitic larvae sometimes called water fleas—that burrow into the skin. They thrive in fresh or brackish water, particularly in shallow, warm lakes with high numbers of waterfowl and snails.

Dr. Soliman Hoshmand of Region Stockholm said the parasites only penetrate the outer layers of skin and typically do not require medical attention. Symptoms can be eased with cortisone cream or cooling ointments, and scratching should be avoided to prevent infection.

Municipalities rarely test for the parasite, as it is not considered a serious health risk and is difficult to detect in water samples. Its presence can fluctuate daily, making monitoring challenging.

Alva Engström, an environmental and health inspector in Stockholm, urged the public to report suspected cases to local authorities so warnings can be posted at affected swimming areas.

Swimmer’s itch usually appears as a rash resembling mosquito bites within two days of exposure and resolves within a week. Severe allergic reactions are rare.