Getting our pets sick: Can humans pass disease to animals?

Some people worry about the diseases they might get from animals. Now our animals might have to worry about what they pick up from us.

Researchers at University of Pennsylvania’s School of Veterinary Medicine are pointing to 38 cases in the past three years where domestic animals appear to have picked up antibiotic-resistant Staphylococcus aureas infections from their humans. Staph is a bacteria that causes infection that can be difficult to eradicate, but it’s not a death sentence – all 26 dogs, eight cats, three parrots and a rabbit identified in this study did recover. Other studies have also shown that horses can have staph infections, but there’s no proof of the bug passing between horses and humans.

Problems in the pets ranged from skin and ear infections to urinary tract infections. When humans get staph infections, they are typically in the skin. However, as many as 1 in 100 humans carry staph bacteria in their noses with no apparent effects, except the ability to transmit to other humans and now, pets. Another possibility for where the animals picked up the bacteria: Vet clinics where they were treated before coming to Penn.

The big issue here is that the staph bacteria is resistant to penicillin and methicillin, making it harder to fight back the infection once it starts. That means we have to use more heavy-duty drugs to eradicate it, risking that the bacteria will also develop resistance to these newer, tougher antibiotics.

Is this cause for worry? Yes and no. Antibiotic resistance is always a concern, because if we don’t have a drug to work against the bacteria, we could be in trouble. But for about 10 years, reports of this kind of infection being passed from human to animal have shown up in medical publications. The difference here is that there are multiple cases, making it seem less rare. Part of this discovery could be related to the better standard of veterinary care seen in the last decade – pet owners are getting medical care for their pets more quickly when a problem comes up, and testing is more widespread.

Most of the time, staph bacteria is present but doesn’t harm anything. Usually it takes something else to irritate the skin and reduce the animal’s immune system. For example, allergies that cause a pet to scratch repeatedly may break the skin and give staph bacteria an opening to get in. The allergies also tax the immune system so it’s not as efficient at fighting the bacteria. Neither you nor the pet carry any more or less staph bacteria than before an infection occurred – it’s just that the bacteria had an opportunity to enter the skin through an abrasion or wound and the body didn’t effectively fight it off.

So, how can you tell if your pet has a staph infection? Just about any infection can have staph bacteria, alone or with other bacteria. If the skin looks infected, if there is a bad odor in the ear, if the pet is having trouble urinating – all these may point to an infection, which may or may not have the staph bacteria. Any time your pet seems lethargic, warm, has a funny odor, or isn’t acting like normal, you can enlist the help of a vet to get to the bottom of the problem.

To reduce the risks of passing the bacteria to pets, humans should follow good hygiene, washing hands frequently and especially when ill or after touching their noses and faces. It’s also a good plan to wash up after petting or playing with your pet. And make sure children in the household also wash before and after playing with pets.

Remember, it’s still very rare for the staph bacteria to pass back and forth between animals and people – we’re just learning that it is possible under some limited circumstances for it to happen. While staph infections are common in both animals and people, it seems unlikely to pass between the two. Penn’s research turned up 38 cases in three years out of all the animals they see, so no need to be alarmed. Just practice the same good hygiene you (hopefully) always have, and be extra careful if you’re diagnosed with a bacterial infection so you don’t pass it along.