Dogs have had some bad PR lately because of some high-profile bites and bite infections in people. So, in the spirit of fairness, I’ll write about a dog as a victim of an attack… from a cat.
A paper in a recent edition of Veterinary Dermatology (Banovic et al 2013) describes necrotizing cellulitis in a dog caused by a cat scratch.
Any infection characterized as "necrotizing" is bad. Necrotizing essentially means "dying," and any time you put "dying" in front of the name of a tissue or body part, you can assume the condition is pretty high on the "badness" scale.
In this case, the dog was a three-year-old Whippet that was bitten on the chest by a neighbour’s cat. The dog developed necrotizing cellulitis due to Pasteurella multocida, a bacterium that is commonly found in the mouths of cats, and one that not uncommonly causes cat bite infections in people as well. Within 24 hours of the incident, there was redness, swelling and pain over the area of the bite. The skin lesion progressed rapidly, with death of the skin over the affected area and development of large, deep skin ulcers, similar to what can happen in people with this kind of infection. Fortunately, the dog was successfully treated with intravenous antibiotics and survived.
Why did this dog develop necrotizing disease?
The reason one infection with P. multocida becomes necrotizing while another infection with the same bacterium does not is unknown The same is true for most cases of necrotizing fasciitis (aka flesh eating disease) in people, which is usually caused by Group A Streptococcus or by Staphylococcus aureus. While saying it’s "bad luck" is highly unscientific, it’s about all we can say in most cases, since there are often no obvious factors that would predispose the affected individual to severe disease, and the bacterial strains that cause necrotizing infection are usually the same as those that cause mild disease and that are found in healthy individuals. So the "bad luck" explanation is about all we have to offer at this point.