Those living around or visiting Pattison Lake in the coming days should avoid the water.

On Wednesday, staff at Thurston County Public Health and Social Services were alerted to the possible presence of the swimmer’s itch parasite in the lake’s waters. A follow-up algae sample also showed microcystin levels, a toxin caused by algae in the lake, at 10 µg/L, 4 µg/L above state recreational guidelines.

Symptoms of swimmer’s itch include tingling, burning or itchy skin, and it typically appears as a skin rash. An allergic reaction to microscopic parasites from snails causes the itch, but it does not usually cause long-term effects.

Algae blooms may be harmful to humans if lake water is consumed, and people should avoid direct contact. Swimming in waters where swimmer’s itch is a known problem is also discouraged.

Pattison Lake is open year-round and offers opportunities for fishing, but those who wade in its waters should take care to avoid marshy areas, where snails are typically found. Fishing should be on a catch-and-release basis during an algae bloom. People should not eat fish caught during an algae bloom.

Anyone who chooses to enter the water should immediately towel dry and shower.