BOULDER CITY, Nev. (AP) — Rangers say a higher than normal waterfowl population at Lake Mead’s Boulder Beach may be to blame for the poison ivy-like rash some swimmers have reported over the weekend.

Authorities with the Lake Mead National Recreation Area say nine people have reported the rash, which rangers believe is Swimmer’s Itch.

The rash comes when parasites that are found in some birds burrow into human skin and cause an allergic reaction.

The Centers for Disease Control and Prevention say most cases of the rash don’t need medical attention, and can be relieved with anti-itch cream.

Rangers say they’re monitoring the shoreline and plan to conduct water quality tests.

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