LAS VEGAS (AP) -- Health officials have a new message for people taking on extreme obstacle courses like the Tough Mudder -- don't eat the mud.
The Centers for Disease Control and Prevention issued a memo this week warning that animal feces in the muddy water along the courses can give participants a bad case of diarrhea.
CDC officials say nearly two dozen people reported coming down sick after participating in a muddy race in rural Beatty, Nevada, in October 2012. The investigation traced the sickness to the bacteria campylobacter coli, and concluded people became sick after accidentally swallowing contaminated water.
Health officials say adventure races in the U.S. drew about 1.5 million participants in 2012. Participants face obstacles such as leaping over a wall of flames and slithering on their bellies through mud.