I too got this itch after soking for an extended period of time at Goldstrike, what I found after doing a search was the following:
"Swimmer's Itch" is an annoying but not serious condition that can develop after using hot springs. The parasite burrows in under the skin, causing itching, swelling, and red welts. To avoid the problem, briskly towel off after using a spring and change into dry clothing. Dabbing rubbing alcohol on the affected area will soothe the itching.