A paper in the journal Orthopedics (Machino et al 2011) describes the case of a 52-year-old man with an infection in the vertebrae of his neck caused by Pasteurella haemolytica. This bacterium (which was renamed Mannheimia haemolytica quite a while ago… I guess their laboratory is a bit behind the times) is most often associated with respiratory disease in cattle. In this case, "because the patient owned 2 dogs and frequently kissed them on the mouth, the cause of infection was thought to be excessive contract with pet dogs."

It’s possible, but I have some issues with this.

  • Despite the assertion in the paper that this bacterium is a resident in the mouth of dogs and cats, I don’t know of much or any evidence supporting this.  A different but related bacterium, Pasteurella multocida, is commonly found in the mouths of healthy dogs and cats, but it’s not the one that caused disease here. The authors state that Pasteurella haemolytica can be found in 71-90% of cats and 21-60% of dogs, yet the papers they cite didn’t actually find P. haemolytica, they found other Pasteurella.
  • The authors also state that the recent increase in pet ownership has caused an increase in P. haeamolytica infections from bite wounds, with absolutely no evidence supporting either an increase in infections caused by this bacterium or any role of pets.
  • This paper takes the typical medical journal approach of blaming the pet with no effort whatsoever to find out if the pet was really involved. Would it have killed them to get some oral samples from the dogs for culture, to see if they could actually find the same bacterium?

It’s disappointing, but not surprising, to see reports like this. It shows a lack of critical thought about the potential role of pets, a lack of care when writing the report, and a weak peer review process for the journal.

Zoonotic diseases are an important issue. However, we need to focus our efforts on real problems, not bad science. This article is so weak and error-filled that it should be retracted, but it’s unlikely anything will happen. I’ll write a Letter to the Editor, which, based on my limited previous experience in questioning poor zoonotic disease science in human medical journals, will likely be ignored. Well, we’ll see.