Sleeping with Our Best Friend Carries Risks of Rare but Deadly Diseases

The percentage of pet owners in the U.S. is increasing (more than 60% of households), as is the percentage who let their dogs and cats sleep on their beds. More than half of dog owners consider their dogs to be members of their family, and approximately 56% let their dogs sleep in their beds. The smaller the dog, the more likely it will sleep with its master. Women are more likely than men to let dogs into the bed. These trends are not confined to the U.S. and have been reported, for instance, in England, the Netherlands, and France.

A professor at the University of California at Davis and an official of the California Department of Public Health in Sacramento searched PubMed for peer-reviewed publications that “clearly documented human exposure to zoonotic diseases by sleeping with, sharing a bed with, kissing, or being licked by pets," i.e., dogs and cats. They found records of 12 separate diseases (13 if bites were included). The diseases were:

1. Plague. Dogs and cats facilitate transfer of infected fleas into the home but, unlike cats, dogs rarely show clinical signs of the disease.
2. Chagas disease (Trypanosoma cruzi). Reported in Argentina; infection rates were significantly higher when infected dogs shared sleeping areas with humans. This disease is a tropical parasitic disease that can lead to life-threatening heart and digestive disorder, brain toxicity, and skin disorders.
3. Cat-scratch disease (Bartonella henselae). This has at least once been reported as coming from a dog licking the handler’s face.
4. Pasteurellosis (Pasteurella multocida or Pasteurella stomatis). One case arose from a cat stealing a baby’s pacifier and using it as a toy before it was returned to the baby. A man got an infection after a hip replacement. The man’s dog slept against the affected leg both before and after the operation. Numerous cases describe a dog or cat licking the person contracting the disease. The disease can lead to edema, vomiting, headache, and diarrhea, with serious complications including septic arthritis and osteitis.
5. Capnocytophaga canimorsus septicemia. A 60 year old patient with chronic eczema died of septic shock and renal failure, probably because his dog used to lick his legs. The disease causes fulminant sepsis and disseminated intravascular coagulation.
6. Staphylococcosis (Staphylococcus intermedius). This bacterium rarely causes human infection, but it has been found in dogs licking a patient after surgery.
7. MRSA infection (methicillin-resistant Staphylococcus aureus). A 48 year old man and his wife had recurrent MRSA infections, which did not stop until the MRSA was eradicated from the dog’s nose.
8. Rabies. Rabies remains a problem in Southeast Asia and sometimes affects travelers, particularly those who allow themselves to be licked by dogs. It is perhaps not widely known that a bite is not the only means of transmitting rabies from a dog to a human.
9. Roundworms (Toxocara canis). The bacterium may be found on a dog’s hair.
10. Giardiasis (Giardia). This is sometimes called "beaver fever" in humans and is a diarrheal infection of the small intestine.
11. Cryptosporidiosis. This is a protozoan parasite that leads to diarrhea, but can be fatal in individuals with compromised immune systems, such as AIDS patients.
12. Cheyletiellosis. Cheyletiella are a genus of mites that live on the skin of dogs, cats, and humans. The mite causes dermatitis, sometimes called walking dandruff.

The authors acknowledge that zoonotic infections acquired by sleeping with a pet are rare, and often involve sleeping with individuals after surgery or who have open sores. The authors also note the bite danger from letting a dog sleep with an infant. Of 109 dog-bite related deaths from 1989 to 1994, 57% were of children under ten years old and 11 were of a sleeping infant.

Administrators of hospitals and other health providers with therapy dog programs should be aware of this report, and should probably confine the visits of therapy dogs to wards and areas where there are no patients who would be vulnerable from contact with a dog. Therapy dog organizations have rigorous requirements regarding dog hygiene, and the risk is small, but an administrator has to consider even remote liabilities.

I must concede that I and my wife sleep with our dog. Our cat is older and doesn’t usually like sharing space with the rest of the family, but for years he slept on or near my wife’s head. Will this study make me change this? No, I’m afraid not, but perhaps if I have surgery or get an open wound of some kind—perhaps—I’ll consider a change of household policy (for myself at least, that being the limit of my authority in the family unit).

Chomel, B.B. and Sun, B. (February 2011). Zoonoses in the Bedroom. Emerging Infectious Diseases 17(2), 167-172. See also Enoch D.A., Karas, J.A., Slater, J.D., Emery M.M., Kearns, A.M., and Farrington, M. (2005), MRSA carriage in a pet therapy dog, Journal of Hospital Infection 60, 186-188; Ensminger, J. (2010), Service and Therapy Dogs in American Society, 191-2.

Additional Note. In Capell v. North Carolina Division of Vocational Rehabilitation Services, 2011 WL 3501894 (W.D.N.C. 2011), a federal court in North Carolina dismissed a number of claims raised by a patient who wanted to have his sugar gliders present in his in-patient recovery room. Sugar gliders are a species of possum. The court found that the sugar gliders were not service animals under the ADA regulations, citing 28 CFR 35.104 and 36.104, which limit the service animal definition to dogs (there was, understandably, no mention of guide horses). The court noted the hospital's "concern for the health and safety of Plaintiff as well as other hospital patients, and the risk of post-surgical infection from animals," describing this as a "non-discriminatory rationale for the denial." The court did not discuss whether this rationale could be applied to limit the presence of a dog in a hospital.