Mud contaminated with sheep faeces was the most likely cause of 161 competitors in a mountain biking event falling ill, a report has said.
An investigation into the outbreak of vomiting and diarrhoea following the Mountain Bike Marathon, in Builth Wells, mid Wales, was carried out by the National Public Health Service for Wales (NPHS).
The 664 riders who took part in the event on Jul
y 5 and 6 were invited by NPHS to complete an internet questionnaire after an initial report of eight people falling sick.
Of the 355 responses, 161 reported symptoms such as diarrhoea and vomiting following the event.
The responses were used to investigate the risks competitors were exposed to.
And the report concluded that the outbreak was probably caused by Campylobacter, spread to the cyclists by mud which was contaminated with sheep faeces.
It said the heavy overnight rain was likely to have contributed to the outbreak by increasing the amount of liquid mud on the course.
The report went on to recommend pre-packaged food being eaten out of the wrapper at future events, avoiding use of soiled drink and food containers, and washing hands when possible.
Dr Sian Griffiths, of the NPHS, said: "We have been delighted with the help we have received from the mountain bikers when investigating this outbreak of illness.
"We would also like to thank the race organisers for their co-operation and our colleagues in Environmental Health at Powys County Council.
"We hope that this report and the recommendations within it will help reduce the risk of something like this happening again."
