Zoonotic disease: Whats the real risk for immunocompromised veterinary clients?

Kristina/stock.adobe.comDespite the many documented psychosocial and health benefits pets offer, many people who are immunocompromised are still advised to relinquish their animals due to the risk for zoonotic disease transmission, despite a lack of evidence demonstrating the need to do so. According to Audrey Ruple, PhD, DVM, MS, DACVPM, MRCVS, from the Department of Public Health in the Purdue University College of Health and Human Sciences in West Lafayette, Indiana, by taking appropriate preventive measures, pet owners who are immunocompromised can minimize their risk of developing zoonotic diseases.

In an interview with dvm360, Dr. Ruple discussed these measures and outlined the key role physicians and veterinarians have to play in educating people about risk levels and how to prevent zoonotic disease.

Who is at risk of contracting zoonotic diseases from pets?

Although pets can be a source of zoonotic disease for all people, some individuals are more at risk than others. Pet-associated disease risks are greatest among people with a compromised or incompletely developed immune system, Dr. Ruple says. These include young children (<5 years old), older adults (≥ 65 years old), pregnant women and patients who have conditions (e.g. HIV/AIDS, cancer) or are undergoing treatments (e.g. chemotherapy agents, immunosuppressive drugs) that weaken the immune system.

Zoonotic diseases and immunocompromised people

“Of the several million immunocompromised people in the United States, 30% to 40% own companion animals,” Dr. Ruple says. She also highlights the predicament that many of these people face when they receive incorrect or incomplete advice.

These people often have to decide whether to keep or give up their pets, she says, because they hear that keeping their pets means increasing their risk of contracting zoonotic infections. “But giving up their pets often means losing their social wellbeing,” says Dr. Ruple. “For many of these people, their pets represent their final remaining comfort in life.”

According to Dr. Ruple, in 1992, when HIV infection was a fatal diagnosis, about 90% of men who were HIV positive were told by their clinicians and friends to give up their pets. But only 5% of the men did.

“The health benefits of the human-animal bond have been quantified,” she says.

The fact is that pet owners are no more likely to develop a zoonotic disease than people without pets are, says Dr. Ruple. Indeed, a 1995 study among patients with AIDS showed that those who had pets were no more likely than those without pets to develop opportunistic infectious diseases, such as cryptosporidiosis, that may be common in animals.1 Another study showed that owning a cat or a dog is not associated with a greater seroprevalence of antibodies to infectious agents such as Anaplasma phagocytophilum, Coxiella burnetii and Bartonella henselae.2

The Centers for Disease Control and Prevention also reports that there is no evidence that animals pose a more significant risk of transmitting zoonotic infections than people do.3

“Pets are being blamed as a source of zoonotic disease without any evidence really existing to prove this,” Dr. Ruple says.

How knowledgeable are physicians and veterinarians about zoonotic diseases?

Many studies have highlighted significant gaps in physicians' and veterinarians' knowledge of different aspects of zoonotic diseases, including the risk for transmission.

Data from one survey show that physicians and veterinarians significantly differ in their opinions about the risks posed to immunocompromised people by various infectious agents, and that communication between the two groups of professionals about zoonotic diseases is lacking.4 In this survey of 310 veterinarians, 96 indicated that they offer special consultation about additional steps for zoonotic disease prevention if they are aware of the fact that a client is immunocompromised. However, 205 of the 310 (66%) veterinarian respondents admitted that the client's health was never discussed.4

Findings from another survey of 1,376 physicians and 181 veterinarians also highlighted factors with important implications for immunosuppressed individuals.5 Only 26% of veterinarians and 33% of physicians correctly identified the zoonotic pathogens that pose the greatest risk to people with HIV infection or AIDS. Also, most physicians (94%) admitted that they either never or rarely initiated discussions about zoonotic diseases with patients who have HIV infection or AIDS.5

This study also once again emphasized the communication gap between these two groups of professionals. All physicians (100%) indicated that they either never or rarely contacted veterinarians for advice on zoonotic diseases. Similarly, 97% of veterinarians had either never or rarely contacted physicians to discuss the risks of these diseases. 

Many physicians also feel uncomfortable educating their patients about the risk of zoonotic diseases. Indeed, many believe that veterinarians should be equally responsible, if not more so, for educating people about the risks of zoonotic disease transmission.4

However, one challenge for veterinarians is that they often do not know when a client is immunocompromised or has other medical conditions that increase the risk of developing zoonotic diseases. And many of veterinary clients may not wish to discuss such details with them. Indeed, one report indicated that only 21% of HIV patients felt comfortable asking their veterinarian about the health risks associated with pet ownership.6

Another study highlighted a lack of awareness of pet-associated disease risks among surveyed parents, and also showed that pediatricians are not appropriately educating parents about these risks.7 Among the 231 parents who responded, most (76%) knew that toxoplasmosis was transmitted by cat feces, but relatively few were aware of other routes of transmission, such as via soil (10%) or undercooked meat (15%). Another 9% incorrectly identified dog saliva as a source of transmission, while 21% said they had no information about the disease.

Similarly, among the 77 pediatricians who responded, most (96%) identified cat feces as a source of toxoplasmosis, but fewer identified undercooked meat (42%) and garden soil (34%) as sources. And 8% incorrectly identified dog saliva as a source of disease transmission. Interestingly, although most pediatricians believed that advising parents about pet-associated diseases was important, most did not provide such advice to families.

How can veterinarians help immunocompromised clients?

Overall, veterinarians should be more proactive in helping to educate clients who are immunocompromised, Dr. Ruple says. 

One simple way to help these clients is by providing access to passive forms of information about zoonotic diseases and their transmission. This may include measures such as providing access to brochures in the clinic, playing videos in the clinic waiting room and sharing information on the clinic website.

She also advises veterinarians to take a more active role in discussing zoonotic diseases with all clients, including those who are immunocompromised. These discussions should occur during routine pet wellness examinations. In particular, clients need education about the types of zoonotic infections their pets may develop and the risks for disease transmission when they handle pets and clean the areas where their pets live.

Veterinarians can also advise these clients about choosing pets. This includes advising them to arrange for a new-pet health check to ensure they adopt only healthy, well-behaved animals and to keep their pets well trained. These clients should also avoid selecting reptiles as pets, Dr. Ruple stresses.

To reduce the risk of pet-associated disease transmission, clients must also pay special attention to their personal hygiene, as well as to general hygiene practices, when handling their pets or cleaning their pets' environments (see sidebar). In particular, “hand-hygiene measures are the most important strategy to prevent infection,” Dr. Ruple says.

Hygiene and husbandry reduce the risk

Advise your immunocompromised clients and their families about these personal hygiene and husbandry measures to keep themselves safe.

Personal hygiene measures

Maintain good general hygiene.

Wash your hands after handling pets or pet food, or when cleaning pets' food bowls or living areas.

Don't allow pets to lick your face.

Clean pet-related wounds immediately, especially bites and scratches.

Use gloves to administer medication to pets.

Supervise children when they wash their hands.

Avoid preparing pet food and feeding pets in the kitchen.

Husbandry measures

If possible, avoid cleaning litterboxes, fish tanks or bird cages, as well as “scooping poop.” Clients who cannot avoid some of these activities should wear gloves when performing them.

Clients who are at high risk for developing zoonotic disease need to be especially vigilant of their pet's health. However, health maintenance practices for these pets involve the same forms of preventive care that veterinarians typically perform for all pets, Dr. Ruple says. These include physical examinations, routine vaccinations, fecal flotations, regular deworming and parasite prevention. Veterinarians should also stress the need for clients to avoid feeding raw foods to their pets and to feed them only high-quality pet food. They should also seek veterinary care immediately whenever their pet becomes ill.

“Routine screening of healthy pets for multiple zoonotic agents is not recommended under any circumstance,” Dr. Ruple says, because there is no evidence of any benefit for this practice. However, if a client who is infected with HIV, for example, has a pet that develops diarrhea, the veterinarian should request a fecal sample from the pet to screen it for zoonotic pathogens such as Cryptosporidium, Salmonella and Campylobacter.8

Joining forces with physicians

“There's a barrier with respect to communication between veterinarians and physicians,” Dr. Ruple says. Given the combination of this barrier and veterinarians' and physicians' knowledge gaps about pet-associated zoonotic disease transmission, Dr. Ruple suggests that veterinarians partner with physicians in the community to help this patient population. Even a simple initiative, such as holding regular journal clubs for veterinarians and physicians in the community, can help improve mutual understanding of zoonotic disease transmission. This continued exchange of information will be beneficial in helping these professionals better advise people who are immunocompromised and own pets.

Veterinarians can also take part in other initiatives, including becoming engaged with a local board of health. This might involve becoming a member of the board, attending the board's meetings or being on call to help address public health issues that arise in the community.

Finally, Dr. Ruple stresses that the benefits of pet ownership far outweigh the risks of disease transmission for most people who are immunocompromised. Most of these individuals do not have to give up their pets, but they do need to take some precautions. She also emphasizes the need for physicians and veterinarians to come together to appropriately advise these pet owners about the risks of pet-associated disease, and about the careful precautions that can mitigate this risk.

References

1.   Conti L, Lieb S, Liberti T, et al. Pet ownership among persons with AIDS in three Florida counties. Am J Public Health 1995; 85(11):1559-1561.

2.   Skerget M, Wenisch C, Daxboeck F, et al. Cat or dog ownership and seroprevalence of ehrlichiosis, Q fever, and cat-scratch disease. Emerg Infect Dis 2003; 9(10):1337-1340.

3.   Centers for Disease Control and Prevention. Guidelines for Environmental Infection Control in Health-Care Facilities (2003). Available at https://www.cdc.gov/infectioncontrol/guidelines/environmental/background/animals.html. Reviewed November 5, 2015. Accessed October 12, 2018.

4.   Grant S, Olsen CW. Preventing zoonotic diseases in immunocompromised persons: the role of physicians and veterinarians. Emerg Infect Dis. 1999;5(1):159-163.

5.   Hill WA, Petty GC, Erwin PC, et al. A survey of Tennessee veterinarian and physician attitudes, knowledge, and practices regarding zoonoses prevention among animal owners with HIV infection or AIDS. J Am Vet Med Assoc 2012;240(12):1432-1440.

6.   St. Pierre LA, Kreisle RA, Beck AM. Role of veterinarians in educating immunocompromised clients on the risks and benefits of pet ownership. In: Proceedings of the Geraldine R. Dodge Foundation Gathering and Reports of 1996 Veterinary Student Fellows; 1996 Sep 27-29; Ithaca, New York. Morristown (NJ): The Foundation; 1996.

7.   Villar RG, Connick M, Barton LL, et al. Parent and pediatrician knowledge, attitudes, and practices regarding pet-associated hazards. Arch Pediatr Adolesc Med 1998; 152(10):1035-1037.

8.   Panel on Opportunistic Infections in Adults and Adolescents with HIV. Guidelines for the prevention and treatment of opportunistic infections in adults and adolescents with HIV: recommendations from the Centers for Disease Control and Prevention, the National Institutes of Health, and the HIV Medicine Association of the Infectious Diseases Society of America. Available at https://aidsinfo.nih.gov/contentfiles/lvguidelines/adult_oi.pdf. Accessed November 5, 2019.

Nicola Parry, BVSc, MRCVS, MSc, DACVP, FRSPH, ELS, is an independent veterinary pathology consultant with Midwest Veterinary Pathology in Lafayette, Indiana.