you missed something, in that it is impossible to get perfectly sterile living animals or plants, and all* of them are carrying a large vaiety of bacteria, viruses, spores, and other animals eggs, etc. everything is an inoculant

* I am aware of various experiments that did attempt to raise animals in perfectly sterile environments, where they died, but the only way to sterilise and maintain sterility, are extream, and largely impossible while keeping any single lifeform, alive.ie: it is far from the default