BMJ Case Reports has a recent paper entitled “Cirrhosis, cellulitis and cats: a ‘purrfect’ combination for life-threatening spontaneous bacterial peritonitis from Pasteurella multocida” (Hey et al 2012). (I don’t think we’d be able to use a title like that in a veterinary journal, but they often get away with titles playing on the animal side in medical journals.)

The case report describes a man who had liver cirrhosis from hepatitis C infection and alcoholism. He went into hospital with a chronic infection of his leg. He’d been seen various times for this problem and various bacteria had been isolated (leading to treatment with various antibiotics). This time, he had severe swelling of his leg that went from his calf to his groin, along with significant accumulation of fluid in his abdomen. Shortly after admission, he deteriorated and became septic (he developed an overwhelming bloodstream infection) and went into liver failure. Blood samples and samples of fluid from his abdomen were tested and the bacterium Pasteurella multocida was isolated. Fortunately, he responded to aggressive treatment.

Upon subsequent investigation, they found out that the patient had a cat, and that cat "had a disturbing habit of regularly licking the serous exudate [leaking fluid] from the patient’s chronic left leg leg cellulitis." (This probably occurs much more commonly than most people think.)

Pasteurella multocida is a bacterium that’s commonly linked to cats, and it’s a frequent inhabitant of the mouth of healthy cats. The cat wasn’t tested but it’s a reasonable assumption that this infection came from the pet. The patient was given “the appropriate advice with regard to the safe cohabitation with domestic animals” but unfortunately they don’t say what that advice was.

This is just one more in a series of reports that show the importance of asking people about pet ownership and pet contact. Asking that question initially can potentially help identify zoonotic disease risks, as opposed to asking the question after the zoonotic pathogen is eventually found when they’re trying to round out the story.

The authors list some ‘learning points’. I’ve copied two important ones below.

• Domestic animals can, under the appropriate clinical circumstances, pose a risk to an immunocompromised host, particularly if adequate hygienic practices are not adhered to.
• Questioning regarding exposure to domestic animals should form part of the clinical history when assessing immunocompromised hosts, allowing early institution of empiric antimicrobial therapy in the appropriate clinical scenario.

They’re both good points, although I’d remove "immunocompromised." While the risk is lower in people with normal immune systems, some risk still remains and pet contact should be queried all the time.