People might assume that diagnostic tests are created when researchers identify a condition that needs a new or better test, then develop the test and prove that it works (and helps with patient). However, sometimes it’s more a matter of a new test looking for a market rather than a disease looking for a test. Sometimes, it’s a matter of an old test trying to maintain a market in the face of new information or better testing. Whatever the situation, the bottom line is that not all available diagnostic tests are useful in all situations.

Bartonella testing is a good example. Bartonella is a strange Genus of bacteria that can cause various diseases in people. Of these diseases, the one most commonly associated with pets is cat scratch disease caused by Bartonella henselaeIt usually causes only mild illness, but serious complications can occur, so it’s something to which we need to pay attention.  

National Veterinary Laboratory, a private diagnostic testing company in the US, is currently promoting their Bartonella test, an old test that only indicates previous exposure to the bacterium, as a way to keep yourself and your family safe. In their promotional materials, they state "We recommend that all healthy pet cats, especially those obtained as strays, from shelters or animal rescue organizations, and those that have had flea infestations, be tested for Bartonella infection."

It’s not surprising that they recommend testing, since they make money off the testing. But what does the evidence say, and what do experts recommend?

They certainly don’t say the same thing as the diagnostic lab. In fact, Guidelines for the prevention and treatment of opportunistic infections among HIV-exposed and HIV-infected children: recommendations from CDC, the National Institutes of Health, the HIV Medicine Association of the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the American Academy of Pediatrics states:

"No evidence indicates any benefit from routine culturing or serologic testing of cats for Bartonella infection or from antibiotic treatment of healthy, serologically positive cats."

So, if an independent group of experts doesn’t think that testing of cats owned by this high risk population is necessary, why would we test every cat?

Why not test all cats? For me, it comes down to what the results tell me, and what I’d do with them. For this type of testing:

  • A positive result means the cat has been exposed to Bartonella at some point, and may or may not be shedding the bacterium. There are no guidelines that recommend treating healthy cats, so I’d focus on flea control along with bite and scratch avoidance.
  • A negative result means that the cat has probably not been exposed to Bartonella, but the test isn’t 100% sensitive. It also only tells me the status of the cat up to the point that the test was performed, not it’s future status. So, the cat could theoretically pick up Bartonella at any point. As a result, I’d ‘d focus on flea control along with bite and scratch avoidance.

Why do a test if the end result is going to be the same either way?

Bartonella henselae (along with some other Bartonella species) is an important zoonotic pathogen which warrants our attention.  However, what we need is greater awareness amongst physicians of Bartonella, better cat bite and scratch avoidance and better flea control practices for pets, not unnecessary testing of healthy cats.

Good diagnostic testing is critical for people and pets that might have disease from Bartonella, but not for healthy individuals.