Kissing your pets can kill you

A common bacteria found in the mouths of healthy dogs and cats can cause a life-threatening infection.

Diana Duong 2 minute read January 14, 2020

A 63-year-old German man shows up to the hospital with a burning sensation in his right leg and pain in both. He has a fever, severe shortness of breath, and his face is covered in small, purplish, rash-like spots. He has dark purple bruises and blood spots all over his right arm and emerging gangrene (death of body tissue) on his fingers.

He was an otherwise healthy man who was suddenly experiencing multi-organ failure.

What’s going on?

It perplexed doctors for four days, until a blood test revealed he had Capnocytophaga canimorsus, a common bacteria found in the mouths of healthy dogs and cats. He had been licked, not bitten, by his dog in the previous weeks.

Published in the European Journal of Internal Medicine, the case study describes the effects of his dog’s lick. He continued to show signs of systemic infection after 10 days of antibiotic treatment, and a CT scan showed that blood flow supply to his spleen and brain was completely compromised and his extremities had become affected with gangrene. His relatives decided to de-escalate therapy and he died after 16 days of treatment.

While C. canimorsus is common in household pets, cases of it in humans are extremely rare. A national study in the Netherlands found the incidence rate was 0.67 infections per million per year. For patients with immunodeficiency, splenectomy, or alcohol abuse, it’s more likely to be severe or even fatal. However, in this case, the patient had none of the above.

Very rarely, severe C. canimorsus infections without biting or scratching have been reported

This case study was also particularly surprising because an infection of C. canimorsus is usually caused by a bite, not a lick. “Very rarely, severe C. canimorsus infections without biting or scratching have been reported,” the researchers in this case study wrote.

To protect the patient’s identity, researchers did not list the type of dog or date of the patient’s illness.

In 2013, a 49-year-old woman from Ottawa became infected with C. canimorsus after one of her pet dogs bit her hand and her other dogs licked her hand. She went into septic shock, which cut the blood flow to her extremities. She eventually needed to have both legs as well as her left arm amputated.

Health Canada estimates that since 1976, approximately 200 human cases of C. canimorsus infection have been reported worldwide.

Researchers of this study warn that pet owners who experience banal flu-like symptoms should urgently seek medical advice if there are additional symptoms that are unusual for a simple viral infection. In this case, it was the patient’s laboured breathing and petechiae (tiny, purplish spots on the skin).


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