Participants of adventure race Tough Mudder fell ill after they swallowed mud contaminated with cattle or swine faeces.
According to the Centers for Disease Control and Prevention (CDC) report, 22 people got sick after getting the infection from the faeces.
Participants of the contest include those from military and civilians in top shape. But the CDC said that the stomach bug found in man-made mud fields caused severe diarrhoea.
Campylobacter bacteria strain found in animal faeces caused diarrhoea which showed its symptoms after few days.
"Campylobacter is one of the most common causes of diarrheal illness in the United States. Most persons who become ill with campylobacteriosis get diarrhoea, cramping, abdominal pain, and fever within two to five days after exposure to the organism," said the CDC report.
The report said that participants fell ill after accidentally ingesting contaminated water during the route which was on a cattle ranch. The problem starts in three days after the race and it stays for a week.
Twenty out of the 22 participants had to take medical care, the other two went directly to the local emergency department without seeking care. One person was hospitalised and needed antibiotics.