Listeriosis is common in ruminants, pigs, dogs, and cats, some wild animals, and humans.
Animals infected with Listeria can show clinical signs of abortions or nervous system disorders. Listeria moncytogenes is the specific bacterium known to cause listeriosis. Listeria thrives in aerobic conditions where the pH is 5.4 or higher. It doesn't do well in very acid conditions. Therefore, the top layers of silage or improperly preserved silage may harbor large numbers of organisms.