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Zoonoses and Human Safety

Veterinarians play a crucial role in protecting dogs, their families, and the public from exposure to zoonotic diseases. Dogs can serve as a sentinel for infections shared with humans. Routine evaluation and diagnostic testing to screen pet dogs for disease vectors and zoonotic infections can enhance recognition of disease risk in people.29 Identifying local outbreaks of canine disease may be the first indication of a new or emerging pathogen that could impact human health. Immune-compromised individuals are at increased risk of acquiring zoonotic disease from pets.

As discussed in the AAHA Infection Control, Prevention, and Biosecurity Guidelines, the veterinary healthcare team is also at risk of acquiring zoonotic infections.30 The practice team should perform proper hand hygiene at all times and alert the team to likely infectious animals so that possible exposure can be mitigated.Wear gloves when there is a potential for contacting a patient’s bodily fluids, excrement, or when having direct or indirect contact with a potentially infectious patient. Particular caution, including limiting the dog’s movement around the hospital, should be taken when examining dogs who may be infected with a zoonotic disease based on appropriate historytaking or clinical signs. Case examples include ill animals with an unknown history or overdue vaccination status for rabies and leptospirosis, especially in the face of neurologic, urinary, or hepatic clinical signs. Additionally, care should be taken when examining dogs with dermatologic changes suggestive of Microsporum canis infection or dogs with a history or high likelihood of a zoonotic multidrug resistant infection (e.g., methicillin-resistant Staphylococcus aureus). Although test specificity is less than ideal, brucellosis status should be evaluated in those dogs at risk. Risk factors for Brucella canis may include sterilization timing (i.e., currently intact or altered later in life), environment (i.e., living in or adopted from a shelter or a country/region where brucellosis is more common), or being used in a breeding colony without a surveillance program.31,32

Common zoonotic diseases are described in many textbooks and review papers and on several excellent websites.33,34 Basic preventive care (e.g., internal and external parasite control, vaccination) protects both canine and human health and is further enhanced by animal and environmental management to prevent pet roaming and avoid situations that may lead to dog bite (see the Behavior page). Advise pet owners to remove feces promptly and safely. Use secure fencing both to keep dogs safe when outdoors and to exclude wildlife. Be aware of regionally occurring diseases and ask pet owners about travel that might expose their pets to diseases occurring in other areas of the country or world. Remain alert to changes in geographic distribution of diseases as incidence and prevalence are continually monitored and updated.35 Control of zoonotic ascarids is particularly important for puppies because of this life stage’s greater likelihood for shedding large numbers of eggs.36 Toxocariasis caused by human infection with Toxocara spp. larvae is a parasitic zoonosis that disproportionately affects children of lower socioeconomic status. Overall human seroprevalence in the United States ranges from 5.1 to 13.9% depending on the test used and the population evaluated.37 Most infections remain subclinical, but severe ophthalmologic and visceral lesions can result. In some surveys, case rates are estimated at 1 per 1,000 people, with ocular toxocariasis possibly responsible for up to 1% of vision loss.38 Preventive strategies include routine deworming of all dogs, prompt removal of feces, and prevention of geophagia.33

Pet food, particularly raw or undercooked meat, is also a source of potential zoonotic agents.39 Many veterinary and human health organizations, including AAHA, do not advocate or endorse feeding pets any raw or dehydrated nonsterilized foods, including treats, that are of animal origin.40 Practice staff or pet owners can monitor pet food recalls via FDA or AVMA websites. Dogs in pet therapy programs or in households with immune-compromised individuals (e.g., elderly, children, <5 yr of age, pregnant, or immunesuppressed individuals) should not be fed raw food or raw treats.1 Safe food handling should be practiced with all pets. Wash hands frequently when handling pet food, avoid feeding pets in the kitchen, use bowls designated only for pets, and wash the food bowls frequently in an area not used by people for preparation or consumption of human food. Encourage pet owners to check food packaging for expiration dates and lot numbers to enable product referrals in case of contamination or recall announcements.

The 2019 AAHA Canine Life Stage Guidelines are supported by generous educational grants from Boehringer Ingelheim Animal Health USA Inc., CareCredit, Elanco Animal Health, Hill’s ® Pet Nutrition, Inc., IDEXX Laboratories, Inc., Merck Animal Health and Zoetis Petcare.