They may be the toughest racers out there, but more than 20 people who got sick after a "Tough Mudder" run in rural Nevada were felled by the very tiniest of obstacles: a germ called Campylobacter.
Cow or pig manure was the likely source of the bug, which thrives in the mud puddles that make the obstacle course runs so much good dirty fun, health officials said Thursday.
The flight surgeon at nearby Nellis Air Force Base and other health officials investigated after three people showed up with bloody diarrhea after the race in October 2012. Tests finally pinned down Campylobacter coli as the cause, and health officials tracked down 22 confirmed or probable cases.