An unassuming lick from a dog is being blamed for the death of an otherwise healthy German man. It’s a strange medical case involving a normally harmless bacterium, but experts say it’s nothing to worry about and that most of us can continue to let our dogs slobber all over us.
Humans have germs in their mouths, and so do dogs. For the most part, dog germs aren’t a huge issue except in rare cases where humans can get infected by Capnocytophaga canimorsus—a normally harmless bacterium—after getting bitten by a dog. But as a new case study published in the European Journal of Case Reports in Internal Medicine shows, a simple lick from a dog can also trigger a bacterial infection.
As detailed in the case study, an otherwise healthy 63-year-old man living in Germany died from such an infection. The man “had been touched and licked, but not bitten or injured, by his dog, his only pet, in previous weeks,” wrote the authors of the case study, led by Naomi Mader from the Department of Medicine at the Red Cross Hospital in Bremen, Germany. Importantly, the man was previously healthy and had no pre-existing health issues, such as a compromised immune system, that could have made him vulnerable to the bacterium.
At first, the man experienced flu-like symptoms and labored breathing. The skin on his face and hands then broke out with small circular red patches and his muscle aches got progressively worse. He decided to seek medical attention three days after symptoms first emerged.
Under the care of medical staff, the man’s condition quickly progressed to severe sepsis, a life-threatening condition in which the body mounts a massive chemical attack against foreign invaders. In this case, that foreign invader was found to be Capnocytophaga canimorsus. Despite “extensive intensive care,” the man’s condition continued to deteriorate until he succumbed to multiple organ failure, dying 16 days after treatment began.
In light of this incident, the authors of the case report say pet owners “with flu-like symptoms should urgently seek medical advice when their symptoms exceed those of a simple viral infection,” which in this case was the severe labored breathing (dyspnoea) and the tiny, circular skin spots (petechiae).
With these helpful admonitions firmly in mind, it’s important to point out that this is an “exceptionally rare” and “peculiar” case, according to William Schaffner, an infectious diseases specialist at Vanderbilt University Medical Center in Nashville, Tennessee.
“The Capnocytophaga canimorsus bacteria is well known to infectious disease specialists as being part of the normal bacterial population that exists in the mouth of dogs, but not in cats or humans,” Schaffner explained during a phone conversation with Gizmodo. Dogs represent a “peculiar ecological niche for this bacterium,” but it “doesn’t cause illness in dogs, and it usually doesn’t cause illnesses in anyone else, either,” he said.
On occasion, dog bites can be “complicated by this bacteria, but even then it’s rare,” said Schaffner, who wasn’t involved with the new case study. “This case in unusual in the extreme. This man’s ‘best friend’ was simply being friendly, doing what thousands of other dogs do every day, slurping or licking their masters on their noses, mouths, and lips—it happens all the time.”
In this circumstance, however, and for reasons that are still unclear, researchers assume that the dog’s lick transmitted the Capnocytophaga canimorsus bacterium to its owner. The incident is so odd, said Schaffner, that it deserved its own case study in the medical literature.
That being said, Schaffner said some people cannot share this kind of intimacy with their dogs, namely individuals who live in an immunocompromised state. This includes people with HIV/AIDS, who have impaired immune systems, or people who have been treated with immunosuppressant agents, such as individuals being treated for bad rheumatoid arthritis or cancer patients recovering from chemotherapy.
There’s nothing wrong with immunodeficient people having dogs, they “just shouldn’t get that intimate with them,” said Schaffner.