True enough, though one needs to keep in mind that *ANYTHING* non-sterile could be a vector for some bug or other if it gets put in a warm, wet place like a vagina or urinary tract (and even an anus, though that "zone" is usually a bit more "resistant" by nature). When one thinks of zoonotic issues in connection with "I fuck my <dog/horse/cat/three-toed sloth/sperm whale/wallaby/whatever>", the PRIMARY (though granted, not exclusive) concern is "something the critter has that it can pass along to you", as opposed to "contaminated object got inside somehow".
Generally speaking, anything that you can catch from your critter by putting your pecker in him/her (or vice-versa) can be caught just as easily by being in the same room with it, petting it, scratching it, brushing/grooming it, feeding it a treat, letting it lick your nose, cleaning up after it, or any other form of contact that doesn't involve "pole into hole". There MAY be some specific exceptions, but if there are, I can't name them.