Who let the dogs out? Pet therapy's hidden danger
According to the article, the key danger is infection. Pets can transmit all kinds of infections through bites and scratches. Animal to human transmission can also occur through contact with animal saliva, urine and other bodily fluids and secretions onto a person's skin or through the nose and other mucous membranes. It's also possible for humans to get infected by ingesting food contaminated with animal fecal and by inhaling infectious aerosols and droplets.
We don't know exactly how often humans get infected by pets, but we know it's a risk factor for bacteria infections like Salmonella, fungal infections, parasites like Toxoplasmosis, and viruses. Although pets don't transmit vector-borne diseases like Lyme and ehrlichiosis, they do bring the ticks and fleas that carry those disease in close proximity to people.
The article in CMAJ says all pets can transmit diseases to people. Dogs, cats, rodents, reptiles and amphibians can transmit Salmonella, Campylobacter jejuni and multidrug resistant bacteria. Reptiles are responsible for 11% of all non-outbreak infections with Salmonella in patients age 21 and under, and 31% of all reptile-associated Salmonella infections in kids under the age of five. Cats are the definitive host for Toxoplasmosis infections. Dogs and cats can harbour Giardia - which causes chronic diarrhea and weight loss.
There are several factors behind the proliferation of diseases in humans that are caused by pets. One is an increase in the number of patients at risk of pet-associated diseases. For healthy people, the risk is fairly low - not so for newborns, kids with leukemia, adults with cancer as well as organ transplant recipients of all ages. Several surveys have found that the general public and vulnerable patients are unaware of the health risks from pets. One study found 77% of households that got a new pet following a diagnosis of cancer got a high-risk pet.
Ironically, another factor may well be the health benefits of pet therapy touted by experts. I'm not saying hospitals are exposing vulnerable patients to pets. What I am saying is that media stories about the benefits of pet therapy may give patients and families the false sense that pets are good for all patients.
That said, there are some clear health benefits to adding pets into the medical mix. Studies have shown that animals can reduce symptoms such as pain, anxiety, depression and fatigue for patients receiving cancer treatment, patients hospitalized with heart failure, kids having dental procedures, veterans and others with post-traumatic stress disorder, and seniors with and without dementia who live in long term care facilities. And it's not just patients who benefit; so too can family members.
Studies have also shown that dogs can be trained to bark when a patient with epilepsy is about to have a seizure. Studies have also suggested that dogs can detect cancer in its early stages because they can sniff out volatile chemicals that are secreted by cancer cells.
However, we need to take special precautions for patients under age five and over the age of 65, pregnant women and patients with cancer and those with compromised immune systems are at risk of pet-associated infections. That means more frequent hand washing, cleaning of floors and countertops and other personal precautions. For pet owners, it also means being more vigilant to pet-associated infections.
I have seen close up the benefits of pets who make the rounds at long term care facilities. The key is to find a sensible balance between benefit and risk.