An elderly lady and her pet Italian greyhound – sounds like the lovely opening to a sweet story doesn’t it? The story, however, is rather dark. According to a recent medical case report, the greyhound was the likely source of an infection resulting in a lengthy hospital stay and potentially fatal sepsis. Thankfully, this particular patient survived, but the story raises some interesting questions about our increasingly close relationship with the domestic dog.
The bug responsible was Capnocytophaga canimorsus, a bacteria commonly found in the mouths of dogs and cats. It’s estimated that up to three quarters of healthy dogs harbour this bacteria in their mouths. These animals suffer no ill effects and, in truth, humans coming into contact with this bacteria rarely suffer any medical consequences.
But, occasionally, problems might arise, especially if you have reduced immune function. With a reported mortality rate of 30%, awareness of susceptibility to Capnocytophaga canimorsus infection is important for groups who might be at particular risk, such as the elderly. The interesting point about this case is that the patient appeared to have acquired the infection via a lick from her dog and not by a bite as is more commonly reported.
Where infection is associated with dog bites, the consequences can be extreme, including gangrene and amputations. The potential for spread of this bacteria from dog licks, which is often perceived as a friendly, bonding gesture by dog owners, might suggest we should re-evaluate how close we get to our dogs' mouths.
Dog bites have long been associated with illness. Rabies remains responsible for about 60,000 human deaths annually, mostly in developing countries. A range of other disease-causing organisms are also known to be transmitted from dogs to humans. Close relationships with our dogs might enhance the transmission of nasties, either direct from the dog, or from a contaminated environment. For example, Salmonella causes severe gastrointestinal symptoms and can be acquired by exposure to infected faecal matter.