Pets serve valuable social roles in society [1,2]. Pets may lower blood pressure, reduce cholesterol and triglyceride levels, and improve feelings of loneliness, while increasing opportunities for exercise, outdoor activities, and socialization .
In a small, randomized, controlled study of 28 patients with chronic age-related disabilities living in a nursing home, patients were randomly assigned to animal interaction ("pet therapy") compared with usual activities (control group) . The "pet therapy" group patients had improved symptoms of depression and a significant decrease in blood pressure values as compared with the control patients.
Despite these benefits, pets present zoonotic risks, especially for immunocompromised hosts [4-6]. The epidemiology of dog-related zoonoses will be reviewed here. The epidemiology of pet-related zoonoses other than dogs is presented separately (see "Zoonoses from cats" and "Zoonoses from pets other than dogs and cats"). The clinical management of specific zoonotic diseases is discussed under the appropriate topic reviews.
A zoonosis is an animal disease that is transmissible to humans. Humans are usually an accidental host that acquire disease through close contact with an infected animal who may or may not be symptomatic.
The American Pet Association estimates that there are approximately 45 million dog owners in the United States, who own a total of about 63 million dogs (http://www.apapets.org). The most common route of infection related to dogs is through bites, especially in children. Dogs bite more than 4.7 million people a year; in 2001, an estimated 368,245 persons were treated in United States hospital emergency departments for nonfatal dog bite-related injuries . (See "Soft tissue infections due to dog and cat bites".)