The dog represents the mainly involved animal species in Animal-assisted interventions (AAI)Is as well as in hospital-based AAT in pediatric oncology patients ^[1][47]. Although substantial benefits have been documented in the literature on the involvement of dogs in AAI, physical contact between humans and animals could cause the carrying of potential pathogens from animals to human beings. Sometimes, in AAI settings the dogs employed might also represent pathogen carriers causing a pathogen exchange from being contaminated by physical contact with infected/haunted subjects and then transferring microorganisms to other patients ^[2][3][2,52]. In particular, it is scientifically demonstrated that pediatric oncological patients have immunodeficiency cancer treatments mediated and therefore are retained to be more susceptible ^[1][2][2,47]. The modes of pathogens transmission can include physical interaction, aerosol inhalation, infected saliva, urine, or feces, as well as contact with contaminated tools ^[4][53].

Several transmissible diseases that can be transmitted by dogs to patients (see Table 12) consist of viral pathogens (Norovirus, rabies) ^[5][54], microorganisms of bacterial origin such as Bordetella bronchiseptica-associated disease, Brucellosis, Capnocytophagosis, Coxiellosis, Cryptosporidiosis, Infections with E. coli, Leptospirosis, Methicillin resistance Staphylococcus aureus, MRSA, including Campylobacter spp, such as C. jejuni, and C. coli ^[6][55]. The most common risk factors associated with Campylobacter spp. occurrence are represented by the dog’s breed and diet, while differences in age and sex of the animal do not seem to have statistical significance.

Considering that younger dogs have an immature immune system and a poorly developed gut microbiota, therefore unable to induce the competitive exclusion principle toward microorganisms, Campylobacter spp. incidence is more easily found in the latter ^[7][56]. In addition, purebred dogs seem to be more easily exposed to Campylobacter spp. coinfection if compared to crossbreed dogs, which appear generally more resistant to disease ^[7][56]. Another potential risk for dogs is Campylobacter spp. transmission from homemade cooked food, especially meat, and is sometimes associated with incorrect food handling and/or cross-contamination from raw foods ^[6][8][55,57]. Dogs involved in AAIs should not be fed raw animal-origin foods within 90 days before service ^[9][10][58,59]

Still, other pathogens that cause zoonoses and could be found in dogs are Pasterurellosis, Salmonellosis, Staphylococcal pyoderma, Tularemia cutaneus, Yersiniosis enterocolitica, fungal contamination, ringworms, parasites (Echinococcosis, Giardiasis, Mange), and visceral larva migrans ^{[2][4][11][12]}[2,53,60,61].

The adoption of different practices and protocols can modulate safety results and outcomes ^[2][13][2,62].

Protocols to evaluate zoonotic-pathogens transmission consist of group A streptococci, Clostridium difficile, vancomycin-resistant enterococci, and MRSA ^[9][58]. The majority of zoonoses are commonly identified and treated. Preventive measures involve internal and external parasite treatments and vaccination protocols; taken together, they are environmental biomonitoring to safeguard both dogs’ and human health ^[2][4][2,53]. An Italian study showed that the most common high-risk zoonotic agents of parasitic origin included Ancylostomatidae, Eucoleus aerophylus, Toxocara canis, Giardia duodenalis, Nannizzia gypsea, and Paraphyton mirabile ^[14][63].

The risk of pathogen transmission depends on contact and time of exposure to the pathogens; therefore, the duration of an AAT session varies from 15 to 120 min, with increasing intensification of the physical contact between the animal and the patient ^{[15][16][17][18]}[4,5,6,64].

Another problem that can be found in AAIs is the patient’s or family’s fear of dogs; one of the exclusion criteria of an animal involved in AAI in such circumstances. In fact, the exclusion criteria can include fear/phobia of animals, cultural attitudes ^[19][65]; unsafe animal behavior ^[20][66]; injuries, such as a fall or bites and scratches, which can happen if handled inappropriately or an inappropriate animal for the therapy environment is chosen ^[21][22][25,67]; allergic reactions such as pet dander ^[23][68]; as well as concerns regarding hygiene/sanitization ^[23][68].

Most protocols suggest that dogs undergo washing and grooming by 24 h prior to contact with patients ^[24][69]. Nevertheless, washing a dog a couple of times during the week can reduce Can f1 from dog hair and coat, lowering the risk of allergic reaction ^[21][25]. Allergies can cause skin irritations, rhinoconjunctivitis, and bronchial asthma, representing a precise contraindication for (in)direct contact with dogs ^[21][25]. Up to now, there is no evidence of the presence of a hypoallergenic dog breed ^[23][68].

Then, from a welfare point of view, the allergological risks of implementing dogs in a hospital or outpatient setting should not be underestimated ^[23][68], and these animals should not interact with patients suffering from allergic asthma. In addition, emergency medication should be available to a trained person on site to mitigate risk in the event of an allergic response ^[23][25][68,70].

Potential zoonotic diseases from cats that can infect humans are listed in Table 12. The most common zoonotic diseases that can be transmitted by cats include Bacillus anthracis, Bartonella species, Borrelia burgdorferi, group A streptococcus, Listeria monocytogenes, Rickettsia felis, salmonella species, tapeworms (Dipylidium caninum, Echinococcus multilocularis), ectoparasites (Cheyletiella blakei, Sarcoptes scabiei), Roundworms (Ancylostoma braziliense), heartworm (Dirofilaria immitis, Strongyloides stercoralis, Uncinaria stenocephala); fungi (Microsporum species, Trichophyton species); protozoans (Toxoplasma gondii); viruses (cowpox, rabies). Some cat-associated zoonoses, such as rabies, are prevented through vaccination. Other infections can be prevented or eliminated through regular testing and the deworming of the animals by veterinarians. In addition, good hygiene should always be maintained around animals.

Another aspect of involving cats is the expression of allergic symptoms from the patients or their relatives. Allergy to cat fur depends on the presence and spread out of the Fel D1 major antigen found in their saliva and dander ^[28][72]. This allergen is produced more by entire male cats than neutered males (due to a partial influence from testosterone) ^{[34][35][36][37][38]}[78,79,80,81,82] and females. No scientific data can confirm the presence of less allergenic breeds of cats ^[28][72]. Two strategies to reduce the problem could be summarized as follows: 1. Vaccination of cats against the allergen Fel d 1 secretion, not commercially available yet; 2. Long-term safety of an anti-Fel d 1 IgY-supplemented diet, available commercially. The availability of this diet helps the veterinary healthcare team to organize, with both owners and human healthcare professionals, measures that can be taken to reduce the environmental burden of Fel d 1 ^[28][72] or in extreme cases choosing a different animal species for the therapy.

An integrated approach targeting the mechanisms causing allergy by dog or cat include allergenic immunotherapy (AIT), subcutaneous-(SCIT) or sublingual-(SLIT) immunotherapy, patient education, allergen avoidance, and pharmacotherapy.

The literature referring to this species is almost scarce and only a few data were possible to be extracted (see Table 12). Rabbits are generally docile animals that are easy to handle, with a low risk of transmitting zoonotic pathogens ^[29][73]. The greater risk when working with rabbits is to develop allergies while biting is uncommon. Specific handling techniques and appropriate protective clothes are necessary to avoid painful scratches with their rear limbs when improperly handled.

Diseases of public health importance in domestic rabbits are rare. The development of disease in the human host usually occurs in the presence of a preexisting compromised immune system. Potential rabbit zoonoses include Pasteurella multocida (the bacterium that lives in the oral cavity or upper respiratory tract of rabbits and can be transferred to humans by bites or scratch) ^[29][73], Cryptosporidiosis, induced by Cryptosporidium, an extracellular protozoal organism, which is transmitted via the fecal–oral route ^[30][31][74,75]. Other rabbit diseases such as salmonellosis, yersiniosis, and tularemia are rare and can be transmitted to humans by wild rabbits. External parasites such as acariasis (Cheyletiella) and dermatophytosis (Trichophyton) may be transmitted to humans ^[31][75].

Several infectious diseases can affect both horses and humans (see Table 12). Zoonotic agents represent the interconnection between human beings, the environment, and animals ^[39][83], thus, their transmission from horse to human can occur through direct contact (e.g., Hendra virus) or indirect contamination such as food products (e.g., Botulism) or vectors like ticks (e.g., Lyme-Borrelioses) and mosquitos (e.g., West Nile Fever) ^[40][84]. Therefore, the incidence of zoonotic-pathogens transmission has a close relation to the immune system of the animal and human beings, pathogen-control protocols, and environmental influence ^[41][85]. The frequency of zoonotic diseases is strictly under control ^[39][83]. No findings have been found on reverse zoonosis, which is a disease that was transmitted from human to horse.

Novel pathogens seem to have a relevant impact on horse/human health and relationships. The most emblematic case of emerging disease is the Hendra virus (HeV), which was considered the leading cause of mortality in both human beings and horses in Australia. This virus is a part of the paramyxoviridae genus, which has as a natural reservoir the flying foxes. The transmission way of the above virus is the direct contact of people with the secretions of contaminated horses ^[42][86]. Middleton and coworkers (2014) ^[43][87] developed an anti-HeV vaccine for horses that provided health benefits to humans as well as to environmental health too, meeting the spirit of a One Health approach. Recently, the pandemic of coronavirus disease 2019 (COVID-19) has triggered possible questions regarding the involvement of horses as virus reservoirs. In the USA it was described that about 10% of horses were positive for β-coronavirus ^[44][88], one of the potential sources of COVID-19. At present, no scientific evidence of a direct relationship between human coronavirus and that of horses has been reported ^[3][52]. No literature has been detected regarding the direct transmission of equine-human zoonotic agents during EAI. The public should be instructed and trained before interacting with the horse; furthermore, legislation with formal and social permission to work with the horse should be necessary. While integrated medicine is now related to zoonosis prevention, other One Health aspects are important, such as pathogen-control protocols and manufacturing, safety, and quality control of vaccines as well ^[32][76].

Among equine species, donkeys are also employed in assisted therapy in elderly people with mental disorders ^[45][46][89,90] or children with autism spectrum or motor disabilities ^[47][48][91,92]. These animals seem to be excellent facilitators in the motivation-building process, being able to stimulate the child’s development promoting psychoaffective and psychocognitive development processes ^[47][91]. The most important selective feature of donkeys for AT is their temperament evaluated by numerous behavioral tests used in horses too ^[49][93]. Nevertheless, knowledge of donkeys’ responses to standardized behavioral tests should be improved ^[50][94]. As reported by De Rose et al. (2011) ^[47][91], the choice of the donkey is based on its ethological characteristics, primarily its size, which makes the donkey an unavoidable but not intimidating interlocutor. Thanks to its physical structure, the donkey is physically well-accepted, offering an opportunity for contact and space sharing. When confronted with a new situation, the donkey is neither impulsive nor anxious and instinctively curious ^[50][51][94,95].

No literature regarding zoonotic agents’ transmission from donkeys during AAIs has been found, with the exception of Hydatidosis and toxoplasma infections where their zoonotic potentials have been studied more. Bacterial zoonoses such as brucellosis, leptospirosis, and salmonellosis have been described mainly in equine. In contrast, rabies and Equine encephalomyelitis viral infection have been reported in donkeys more than any other viral zoonoses ^[33][77].

The prevention and control measures put in place and the education of the public about them represent the way to prevent possible human infections.