In rare cases, a dog's lick can carry more than just love

It’s common knowledge a dog bite might warrant a trip to the doctor, but could a friendly puppy lick be dangerous too?

It’s possible – but rare – for close contact with the family pooch to transmit bacteria that can cause dangerous blood poisoning, according to a new case study published in the British Medical Journal’s BMJ Case Reports.

The case report – meaning a detailed description of a striking diagnosis in an individual patient – detailed the unusual story of a 70-year-old Caucasian woman who developed slurred speech and became unresponsive while on the phone to a relative.

Paramedics discovered the woman slumped in a chair in the home she shared with her Italian greyhound. She was diagnosed with severe sepsis, or blood poisoning. Doctors eventually determined she had been infected with Capnocytophaga canimorsus a germ commonly found in the saliva of cats and dogs.

“Neither scratch nor bite was established, although close petting including licks was reported,” the authors wrote. “A full recovery was made following two weeks of intensive care support and broadspectrum antibiotics.”

The paper said that the lesson for doctors was that infection “may occur in the absence of obvious bites or scratches and should always be considered in cases of severe sepsis in pet-owning elderly patients.”

Lead author of the paper, Dr James P Wilson from the Department of Medicine for the Elderly, University College London Hospitals NHS Foundation Trust, told The Conversation that the case detailed “was a very rare event”.

“There have been 13 cases of sepsis involving Capnocytophaga canimorsus since 1990 in the UK; equating to an incidence (at least in the UK) of approximately one case per 150 million people per year. You are about 150 times more likely to be struck by lightning! And, of those 13 cases only a handful were associated with licks,” he said.

“Crucially, the message is not to scare people away from being close to their dogs. The message is more directed at hospital doctors to think about animal transmitted infections generally, when a patient – particularly with immune dysfunction – presents with sepsis.”

Wilson said more caution should be taken with very young children, particularly in the first months when the immune system is still developing. Care should also be taken with immunosuppression, such as people with no spleen, those with liver and alcohol problems or people undergoing chemotherapy.

Dr Vincent Ho, a clinical academic gastroenterologist from Western Sydney University, who was not involved in the findings, said the case highlights a quite uncommon but interesting reaction.

“I would stress that such reactions are very, very rare, and shouldn’t prevent us from having close contact with pets,” he said.

“This case study is saying that this is an elderly person with fairly normal immune system, who developed a very severe reaction to this bacteria. So the elderly, along with the immune suppressed, are important groups to consider. If they’re very unwell, they should keep their distance from their pets.”