It is much more likely that they will just transport it to their people and not be affected themselves. For whatever reason, they are not ver likely to react to it.
I took a pup to the vet with a raised and blistery rash was was assured that it was NOT poison ivy because a reaction was so rare in dogs.
However, I know many people who won't pet other peoples' dogs during poison ivy season because they are so sensitive to it that it will transfer to them from the dogs.