My mother often warned me that “if you lie down with dogs, you get up with fleas.” Of course, she was speaking metaphorically about boyfriends, but Bruno Chomel, DVM, PHD, professor in the department of population health and reproduction at the UC Davis School of Veterinary Medicine, has a more literal reading of that phrase. His recent research has shown that sleeping with pets puts you and your pet at risk for zoonoses, diseases transmitted between animal and human. “Pets in the bedroom are fine, but it’s better if they stay out of your bed,” Dr. Chomel told me.

In truth, it is rare that pet owners get sick from their cats or dogs, but it can and does happen. Illnesses you can acquire this way include…

Tickborne diseases (Lyme, Babesiosis, Ehrlichiosis). Your pet may be harboring diseased ticks in its coat. When you are in close proximity, there is a danger of the ticks crawling onto you and infecting you as well. The risk is heightened if the pet is in your bed because you are spending long hours close together… plus the ticks can get into the bedding and then onto you even when the pet is not there. Tickborne disease symptoms to watch for include aches, fever, rashes and fatigue. You are at risk for infection even if your pet is asymptomatic.

Methicillin-Resistant Staphylococcus Aureus (MRSA). A dangerous bacterial infection that is resistant to most antibiotics, MRSA can be transmitted when the bacterium enters the body through a cut or sore. Pets can carry the infection on their skin or in their nostrils even when they don’t have symptoms of illness, and it can be transmitted to humans by skin-to-skin contact or face-licking and to pets by close contact with humans. If you or your pet has painful, swollen sores that have pus or other drainage, seek medical help immediately. MRSA moves very fast and, if not caught early, can be fatal.

Cat Scratch Disease (also known as cat scratch fever) is carried by 15% to 30% of cats — and is more likely to be carried by kittens than adult felines. This infection is caused by the Bartonella henselae bacterium, which is mainly transmitted by cat scratches. Within 10 days of exposure, you will experience a raised lump at the site of injury, followed by swollen lymph nodes, headaches and fatigue. This is typically not a serious disease. In fact, it often needs no treatment, though some cases are severe enough to be treated with antibiotics. If your symptoms do not clear up within two to three weeks, or are continuing to worsen, check with your doctor.

Bacterial Meningitis affects the brain and spinal cord, causing high fever, headache and stiff neck. Some forms are contagious through exchange of respiratory or throat secretions — yet another reason not to let your pet lick your face. Bacterial meningitis is easy to treat with antibiotics if caught early. With no treatment, it can be deadly.

Bubonic Plague. Most associate this disease with the “Black Death” that ravaged 14th-century Europe. Today it is very rare, but it hasn’t been eliminated in the US. Transmitted by infected fleas, bubonic plague is not just an historical issue — there were small outbreaks in the US in 1974 and 1983 and two cases in 2010. Studies have shown that the occurrences were probably caused by cats or dogs sleeping in the owners’ beds. Symptoms include chills, high fever and muscle pain. Untreated, there is a 50% to 70% chance of death. Treated early with antibiotics, the risk for death falls to 10% to 15%. “This is an extremely rare event, but pet owners should be aware of the possibility,” said Dr. Chomel.

Infants, toddlers, the elderly, pregnant women and people who are immunocompromised should never sleep with a pet. The immune systems in these people are not as strong as those in healthy, younger adults, so there is a heightened risk of contracting infections. And the following precautions apply to everyone…

Do not kiss your pet, and do not let it lick you. (Keep a box of baby wipes or sanitizing gel by your bed to immediately wipe off saliva if you can’t bear that rule.)

Take your pet to a veterinarian for regular checkups.

Make sure your pet is up-to-date on all its shots.

Give your pet monthly heartworm and regular flea and tick preventives.

Cover any weeping or oozing abrasions (yours and the pet’s).

Keep your cat indoors.

Shampoo your dog monthly.

Also: Never sleep with exotic pets or wild animals. Not only can their behavior be dangerously unpredictable, they may easily be carrying bacteria, viruses or fungi that can infect you. Snakes, lizards and turtles, for example, can transmit salmonella.

Important: “If you have any unexplained symptoms, or if your pet has been diagnosed with a transmittable disease, see your health-care professional immediately,” warns Dr. Chomel.