Yes, they do. Wild caught minnows, gizzard shad from the fishing trip, and topminnows, as well as the mosquitofish can be a reservoir for NUMEROUS parasites, and bacterial pathogens, and because their biology has coexisted with these pathogens for millennia, they might not show any symptoms. In other words, it's COMMON for these parasites to live on the fish without causing them obvious harm. They should be considered infectious to the extreme.