Foxes are mammals with immune systems similar to humans, but they have been exposed to the various strains of salmonella every since they evolved and some strains are species specific.

At one point they did then they evolved the body systems to handle the bactera; after all this is part of their natural diet. But, occasionally they do still get sick as a new strain developes or a specific strain crosses the species barrier and so attacks them.

mammasli… just points out the method the foxes evolved to avoid expose to salmonella, in this case they pass it through their system before the bacteria has a chance to take hold. But, any exposure to the bactera inside of the digestive system can allow infection by the bacteria.

by the way a gizzard A gizzard is "a specialized stomach with a thick, muscular wall used for grinding up food. It is found in birds, reptiles, earthworms, some fish, insects, mollusks, and other creatures. In certain insects and mollusks, the gizzard features chitinous plates or teeth. (http://en.wikipedia.org/wiki/Gizzard)"

Chickens really eat stones to help their digestion; this is because they don't have teeth, except the specialized egg tooth that chicks have to break out of the shell and then they lose it.

An animal won't get Salmonella if fed a raw diet unless it has been feed/eaten commercial or cooked food just hours prior to eating anything raw that might contain the germs. That is because commercial/cooked food takes longer (24 hours compared to for them to digest. It then backs up the raw and gives the germs more time in the dark and damp digestive system to colonize and become a problem