I would use it without a second thought.
I spent the day retrieving dummies and toys from the floor of a plane and airport and didn't think anything of it. I probably should have read this thread first.
I had been travelling to sick my ill dad, who is severely immune comprised at the moment. I am very careful about hygiene around him. My toddler with a healthy immune system however, will be perfectly fine with a nappy off the ground. She also uses second hand MCNs, I can only imagine the uproar that might cause.
I had severe cystic acne as a teenager. I went to many doctors and dermatologist and I don't recall any of them mentioning mud as a cause. It was finally cleared with roaccutane and thankfully I didn't have to give up jumping in muddy puddles.