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Lick of death: How one woman's pet almost killed her

Many of us enjoy friendly licks from our furry companions, but one woman’s affectionate pet nearly killed her.

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Owning a pet can be risky for anyone with a suppressed immune system. But there's good news for the rest of us.
A friendly lick from her Italian greyhound almost had fatal consequences for a British woman. Somehow a bug, found in the mouths of healthy cats and dogs, ended up in her bloodstream. Known as Capnocytophaga canimorsus, it can cause conditions ranging from the bacterial skin infection cellulitis to life-threatening blood poisoning.

One study reported that about 16% of dogs carry C canimorsus as part of the normal bacteria in their mouths. “It loves growing in carbon-rich environments such as saliva,” says Dr James Wilson, who compiled a report, “Lick of Death”, after treating the patient at London’s University College Hospital.

He was intrigued because this is such a rare condition, particularly in the absence of a bite or deep scratch. “There was no evidence of damage to the skin and the patient denied being bitten,” he says.

Even when a bite is present, the condition can be tricky to diagnose because the wound may be clean. This patient was only hospitalised after developing slurred speech and becoming unresponsive while on the phone to a relative. She was found to have severe sepsis, suffering organ failure as a result.

“She was very sick,” says Wilson. “She spent time in the ICU as she needed support for breathing and was on strong antibiotics for a month.”

Although the condition is fatal in about a third of cases, the patient made a full recovery and was able to return home to the much-loved pet she had no intention of giving up.

The idea that a dog’s mouth is cleaner than a human’s is a myth. It has its own legion of germs and one 2015 study found that oral-to-oral transfers of bacteria from dogs to people can cause gingivitis and periodontal disease.

Nevertheless, surveys show that more than half of us sleep with our furry friends and allow them to lick us. Wilson stresses the message of his report isn’t that you should never do that. However, extra care should be taken around anyone with a suppressed immune system, including infants, the elderly, alcoholics, people having treatments that make them vulnerable to infection and those who have had their spleen removed. Basic hand washing after handling pets is important.

Thankfully, most diseases passed on by a lick or a bite – such as rabies and brucellosis – are no longer a risk in developed countries. More common are less-serious infections such as cat scratch disease, which occurs particularly in children and is caused by a scratch or bite from an animal infected with the bacteria Bartonella henselae. It can also be spread by cat saliva contact with broken skin or exposure to cat fleas, and may result in fever, headache and lymph-node swelling. “Rarely is it serious,” says Wilson. “A short course of anti­biotics and it’s better.”

The risks of pet ownership are easily outweighed by the benefits. For a start there is the boost to our emotional health – simply patting an animal has been shown to reduce blood pressure and increase levels of brain chemicals, such as dopamine and oxytocin, believed to enhance feelings of well-being. Then there is the advantage to our immune systems. There are plenty of studies showing that young children who grow up in a home with a cat or dog are less likely than those who live pet-free to get sick. They also have a lower risk of developing allergies and asthma.

In a new study from Yale University, researchers emphasised the vital role cats and dogs play in microbial exposure. Aside from carrying their own families of microbes, they bring common bacteria and fungi from the outdoors into the home, so create a wider array of good bugs to help “train” our immune systems.

As for Wilson, his experience with the patient who almost died as a result of a lick hasn’t put him off the idea of pet ownership. “Not at all,” he says. “I’d love to have a dog if I didn’t live in London and work such long hours.”

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