Bobbing for stars where untreated dung would enter your mouth and ears would be one of the most reckless acts of any game show, ever, let alone one containing (used loosely) celebrities. I really don't know if it's been pasteurised to the hilt or just plain fake. The risks in actual dung are bacteria, worms and fungal spores that no OH&S would allow, even after treatment. There are tiny African worms that die and clog the lymphatic system irreversibly. I cannot imagine anyone in the production company taking responsibility for actual dung ingestion. Given that there is no intent to hurt the stars, I think it's all about perceived threat. You just need to make it smelly, and tell a story.
Regarding Bear Grylls eating bear dung, that would be potentially worse, as bears have one of the most parasite riddled digestive tracts on the planet. You would lose more nutrition from the trots than any benefit, and risk bubonic plague. He also squeezed water from elephant dung....but he also disclaims factuality and has used men in bear suits.
I do notice how the contestants use footwear quite religiously. I wonder if that's due to ticks or foot burrowing worms. They seem to wear wetsuit shoes very carefully at times.