According to the FDA, "Listeria monocytogenes rarely causes illness in dogs, but it is possible. Dogs can have mild symptoms such as diarrhea and vomiting." In more severe — though rare — cases, listeria can cause muscle pain, fever, breathing problems, and even death.
It's important to keep in mind that even if a pet doesn't show any symptoms, it can still be a carrier of the bacteria and spread it to humans. Symptoms in humans may include headache, fever, headache, nausea, muscle aches, stiff neck, abdominal pain, diarrhea, confusion, loss of balance, and convulsions. Young children, elderly people, pregnant women, and those with weakened immune systems are also particularly vulnerable.
Salmonella, however, has a higher chance of making your pet sick, particularly if they are very young or have a weakened immune system. "Pets with Salmonella infections may be lethargic and have diarrhea or bloody diarrhea, fever, and vomiting," according to the FDA. "Some pets may only exhibit decreased appetite, fever, and abdominal pain." Similar to listeria, pets that don't exhibit symptoms can still be carries and infect humans and other animals.