Table 1.

Overview of the Articles Examined: Epidemiological Studies, listed by type and chronologically

Authors, Year	Study Design	Goals	Evaluated	Measurements	Covariates	Findings
(Boyle et al., 2019	Epidemiological Retrospective Cohort Study and Survey Review	Prevalence of zoonotic pathogens in therapy animals, and survey of handlers’ understanding of the risks of zoonoses and their adherence to infection control practices	Screening test results from 22 dogs and 2 cats, with a survey of 40 registered therapy animal handlers.	Annual fecal parasitic float and bacterial culture, nasal & perianal MRSA/MRSP skin cultures; One-time structured quantitative surveys of handlers	N/A	17 total positive results of the 118 infectious disease screenings performed, 14 of which were potentially zoonotic organisms. 70% of handlers expressed no concerns regarding infectious disease transmission in AAI settings.
(Gerardi et al., 2018)	Epidemiological Cross-sectional Study	Study looked for protozoan Giardia duodenalis and zoonotic gastrointestinal nematodes over the three-month study period in dogs training for AAI.	Fecal samples from 74 dogs, and demographic questionnaire data	Fecal parasitic exams	Dog age, breed, sex, health status,	Authors found 18/74 (24.3%) positive fecal samples - 8 with Giardia, 3 with co-infections of multiple gastrointestinal parasites.
(Linder et al., 2017)	Epidemiological Cross-Sectional Survey	Surveyed healthcare facilities, as well as AAI organizations, about animal visitation guidelines.	45 eldercare facilities, 45 hospitals, and 27 therapy animal organizations	Survey assessed existing health and safety policies related to AAI programs	N/A	Health and safety policies varied widely and potentially compromised human and animal safety. Hospitals had stricter guidelines than elderly care facilities, which had stricter guidelines that AAI organizations.
(Chubak et al., 2017)	Epidemiological Retrospective Cohort Study and Survey Review	Pilot study on the risk of hospital-acquired infections following an AAI session in a pediatric oncology inpatient clinic	Electronic medical records from 19 pediatric patients, as well as patient, parent, and healthcare provider surveys.	Newly acquired infection cases of the participants for 14 days following an AAI session	NA	Eight of the 19 patients developed a hospital-associated infection following an AAI session. However, this could not be attributed to AAI therapy sessions, as there was no control group to compare whether the infections resulted from exposure to AAI versus exposure to the hospital.
(Snipelisky et al., 2016)	Epidemiological Retrospective Cohort Study	Pilot study to test the feasibility, receptiveness and safety of AAI in hospitalized patients awaiting heart transplantation.	11 patients followed for 12 months, receiving 146 therapy sessions.	Medical record review for documented infections; also surveys of patient receptiveness to AAI therapy.	N/A	Authors found that while maintaining strict institutional infection control policy, no reports of infection or issues with intravenous lines, central lines, or ventricular assist devices, were observed during the study period.
(Coughlan et al., 2010)	Epidemiological Prospective Cohort Study	Prevalence rates of MRSA in 12 resident animals at hospice	11 cats and 1 dog, over course of 8 weeks	1 nasal swab per week	Health status of animal	Author found 2 of the 11 cats were positive for MRSA (5 out of 8 samples for one animal, and 2 out of 8 samples for the other), all USA100 healthcare-associated strains.
(Lefebvre & Weese, 2009)	Letter to the Editor: Case Report	To show the potential for therapy animals to become colonized, not just transiently contaminants, with nosocomial infections	26 therapy dogs with 26 human handlers	Paws and haircoat of each dog, and handler's hands, before and after therapy visit		No positive pre-visit samples, 1 dog (4%) acquired C. difficile after a visit, and one human was positive for MRSA after petting a therapy dog, suggesting that dogs can became contaminated with pathogens during AAI visits, and can transmit pathogens to humans.
(Lefebvre et al., 2009)	Epidemiological prospective cohort and nested case-control studies	To compare the risk of acquiring a pathogen between therapy dogs that visited hospitals versus therapy dogs that visited other venues (classrooms, etc).	96 therapy dogs that visited hospitals and 98 dogs that visited other AAI events.	Fecal and nasal samples from the dogs were collected every 2 months for a year	Dog diet, dog illnesses, and antimicrobial use within the home	Therapy dogs that visited hospitals were almost 5 times more likely to be contaminated with healthcare associated pathogens (IRR 4.7 MRSA, 2.9 C. difficile). Amongst those, therapy dogs that licked patients’ hands were more likely to be contaminated.
(Lefebvre et al., 2008b)	Epidemiological Prospective Cohort Study	To determine if pathogen shedding is different in therapy dogs fed raw meat diet versus not	200 therapy dogs	Fecal samples collected every 2 months for 1 year	Clinical diarrhea, pig-ear consumption	Therapy dogs fed a raw meat diet were significantly more likely to shed pathogens, including antibiotic resistant strains. The authors recommended these dogs be excluded from AAI programs.
(Lefebvre et al., 2006c)	Epidemiological Cross-Sectional Study	Evaluate dogs visiting hospitals for possible zoonotic disease pathogens	102 visitation dogs (includes therapy animals and pets visiting owners)	Fecal sample, hair-coat brushings and one rectal, aural, nasal, oral and pharyngeal swab were collected from each dog and tested for 18 specific pathogens.	Canine demographic details and medical history	Zoonotic pathogens were found in 80 of the 102 dogs (80%), which indicates that these dogs can spread pathogens. The authors concluded that more information is needed on risk factors and transmission routes to better inform infection control policies
(Lefebvre et al., 2006b)	Epidemiological Cross- Sectional Survey	To determine the distribution of canine-visitation programs in Ontario and to characterize the nature of the programs the dogs are affiliated with.	Surveys from 223 hospitals and 90 therapy dog handlers	Surveys from hospitals regarding their usage of AAI programs. Surveys from therapy dog handlers regarding where they volunteer.	Hospital type (acute versus chronic care), dog demographic s (age, sex, breed).	Acute care wards were 5.1 times more likely than other wards to prohibit therapy animals. Handlers reported highly variable screening protocols and infection control practices; 18 owners (20%) said they did not practice any infection control and 36 owners (40%) were unable to name one zoonotic disease
(Lefebvre et al., 2006a)	Letter to the Editor: Case Report	Report of a toxin-variant strain of C. difficile in an apparently healthy therapy dog.	1 dog that was a part of the cross-sectional study described above	Fecal sample	N/A	This canine isolate is indistinguishable from the major strain implicated in outbreaks of highly virulent CDAD around the world. The recurrent exposure of this dog to human healthcare settings suggests that the animal acquired this strain during visits to the hospital.
(Caprilli & Messeri, 2006)	Ecological hospital-based medical record review	Determine rates of hospital-acquired infections before and after the implementation of an AAI program, and patient-reported enjoyment	138 pediatric patient participants and aggregated hospital-wide infection rates	Cases of newly acquired infections prior to introducing therapy dogs, and one year after dogs present in hospital	NA	Authors found constant rates of hospital infections after 1 year of dogs being present in the hospital weekly, compared to the previous year, and no documented contagious diseases were transmitted by dogs during their presence in the hospital.
(Enoch et al., 2005)	Letter to the Editor: Case Report	Describe a case of a therapy dog acquiring MRSA during a therapy visit to a hospital	1 dog	Nasal, head and paw swabs before and after therapy visit	N/A	The dog was negative for MRSA on entering the hospital, but was found positive when leaving, indicating patients may spread MRSA to therapy dogs.
(Sillery et al., 2004)	Letter to the Editor: Case Report	Describe a case of a patient with Pasteurella peritonitis that was suspected to be transmitted from the pet cat.	1 human patient with a pet cat	N/A	N/A	Therapy animals can potentially transmit Pasteurella multocida, a pathogen that can cause peritonitis in patients undergoing peritoneal dialysis. This is the first documented case of suspected transmission of the pathogen from animals, and introduces a novel control point for AAI programs.
(Waltner-Toews, 1993)	Epidemiological Cross-Sectional Survey	First documented attempt to understand risk associated with AAI. Surveyed animal care facilities to determine the prevalence of AAI programs, concerns and experiences with AAI, and zoonotic disease precautions taken to prevent transmission	150 systematically selected United States animal care agencies and 74 Canadian humane societies	N/A	N/A	Half of the respondents expressed concern over zoonotic diseases, but few were based on actual experience. Less than half consulted with a human health professional about infection control and only 10% had written guidelines for prevention of zoonotic disease transmission.