Last week the media headlines warned us that we shouldn't sleep with our pets. Doing so could make us sick. Well, this week, the review article that inspired these headlines, "Zoonoses in the Bedroom," is finally out on the Center for Disease Control's website and available for everyone to read.
In this peer-reviewed article, the authors, veterinarians Bruno B. Chomel, a professor of zoonoses at the University of California, Davis and Ben Sun, the state public health veterinarian for the California Department of Health, searched PubMed for peer-reviewed publications that clearly documented human exposure to zoonotic disease by sharing a bed with, kissing or being licked by pets.
What does the study really reveal? Contrary to what was emphasized in last week's headlines the greatest danger was not in sleeping with pets, but in letting pets lick humans.
Sleeping with Your Pets May Not Be So Bad
The link between sleeping with a pet confirmed to carry a specific disease and exposure to that disease was not that common, but did occur. For instance, in a study of one outbreak of bubonic plague in New Mexico in 1974, one patient who had the plague had slept with his flea-infested cat and noticed flea bites the following morning. Another study looked at 23 cases of cat-associated human plague in the Western United States. In one of the cases a nine-year-old boy from Arizona had handled and slept with a sick cat. It's unclear from the review paper whether a clear link between infected cat and human were shown in each case.
In addition to bubonic plague, a few case of Chagas disease have been associated with sleeping with dogs that were harboring the responsible organism. These humans most likely showed vague signs of fever and general malaise during the early stages of disease, which is most common in Central and South America.
All other cases described in this review article were related to other forms of contact. For instance the review cites a number of people who got cat scratch fever, which is generally transmitted to humans when they are scratched by a cat that harbors Bartonella henselae, infected fleas and flea feces. But a few cases have been associated with sleeping with or being licked by a household pet.
So far it seems like the real moral is that you should get rid of fleas -- something that is really easy if you actually follow your veterinarian's directions so that you use flea products correctly. A possible reason for flea product "failure" is that the products are working just fine but the owners have not followed the instructions.
Avoid Letting Your Pet Lick or Kiss You
In their report, the authors make a much stronger case for preventing pets from licking you. They cite numerous cases in which humans have contracted Pasteurella, a bacteria that normally lives in the mouth of both dogs and cats. In one case, a patient's entire knee arthroplasty site became infected after the patient's dog licked a small wound on the third toe of the leg that had been operated on. And in another case, a 48-year-old obese woman developed a wound abscess six weeks after a hysterectomy for endometrial cancer. Her cat had licked the wound. In a third case in France, a 67-year-old patient with chronic pus-filled discharge from his right ear developed meningitis. His dog frequently licked his right ear and the cultures from the dog's saliva also grew the particular strain of Pasteurella.
In one study of 24 pet owners in Japan, 19 who had not kissed their cat had no Pasteurella stomatitis in their oral cavity. But three of the five pet owners who had kissed their dog or cat did have P. stomatitis in their mouth. Additionally, a 44-year-old woman who admitted she regularly kissed her dog's face and fed it by transferring food mouth-to-mouth developed Pasteurella multocida meningitits.
Other infections you can get from your pet
Other infections from pets include intestinal parasites such as roundworms, hookworms, giardia and Cryptosporidia. But close contact is not required for transmission of these organisms.
What's the overall risk?
Overall, the risk of getting an infection from your dog or cat is relatively low, especially if you control fleas and avoid letting your pets lick you and your wounds. In my view, there are three take-home messages:
1. Keep your pet healthy and free of fleas and other parasites that may be transmissible to humans.
2. Avoid letting your pet lick you, especially on a wound or surgical site, and especially if you are immune-compromised.
3. If you develop a weird infection that is caused by an organism carried by pets, have your veterinarian check your pet so that your pet does not remain a source of re-infection.
You can read the full article "Zoonoses in the Bedroom" in the journal Emerging Infectious Diseases or download it from the CDC's website.
To get more of my tips about how to avoid catching a zoonotic disease from your pet, read How to Sleep Safely with Your Pet.