For example, the association of B. henselae infection and uveitis in cats was first made in an individual uveitis case that ultimately responded to doxycycline therapy.24 We subsequently found Bartonella antibody production and DNA in the aqueous humor of cats previously presumed to have idiopathic uveitis.25 A recent series of feline ocular disease cases thought to be caused by bartonellosis were responsive to antibiotic therapy.26 Thus, it appears likely that Bartonella species causes ocular disease in some cats. However, it can be difficult to determine which cats have been exposed and which
cats are diseased. In a recent study, the prevalence rates for Bartonella species antibodies in feline sera were not significantly different for cats with and without ocular disease.27 It's also unclear why some cats develop Bartonella uveitis and others do not. For example, we failed to induce Toxoplasma
gondii or Bartonella species uveitis when we inoculated Bartonella intravenously into cats with chronic toxoplasmosis.28
Testing for Bartonella infection
Blood culture, PCR assay on blood, and serology can all be used to test cats for Bartonella infection. Culture-negative or PCR-negative cats probably aren't a source of flea, cat, or human infection even if they test
antibody-positive. However, bacteremia can be intermittent, and false-negative culture or PCR results do occur, limiting the
predictive value of a single battery of tests. False-positive results can also occur with PCR assays, and positive results
don't necessarily indicate that the organism is alive.
While serologic testing can help determine an individual cat's exposure, both seropositive and seronegative cats can be bacteremic,
limiting the diagnostic utility of serologic testing. Therefore, testing healthy cats for Bartonella species infection with any test isn't currently recommended.19, 29 Instead, I generally only evaluate cats with suspected clinical bartonellosis for Bartonella species infection.
If the results of the Bartonella species tests are negative in a clinically ill cat, the organism likely isn't the cause of the clinical syndrome unless the
infection was peracute and serologic testing was used as the diagnostic test. If the Bartonella test results are positive, keep the agent on the differential list, but exclude other causes of the clinical syndrome.
Administering doxycycline, tetracycline, amoxicillin-clavulanate, erythromycin, or enrofloxacin can limit bacteremia but
does not cure infection in all cats and has not been shown to lessen the risk of cat scratch disease.19 Thus, treatment is generally recommended for clinically ill cats.19
I use a flavored doxycycline suspension (to avoid the esophageal strictures associated with doxycycline tablets) at 10 mg/kg
orally once a day for seven days as an initial therapeutic trial. If the response is positive, I continue treatment for two
weeks past clinical disease resolution or for a minimum of 28 days. If doxycycline is not tolerated or the cat is not responding
at Day 7, I usually prescribe a different drug if I still think bartonellosis is a valid differential diagnosis. I generally
consider azithromycin or a fluoroquinolone as a second choice.26 In my experience, Bartonella infection is not the cause of illness in Bartonella-positive cats that have failed to respond to two drugs with presumed anti-Bartonella activity.
Preventing Bartonella infection
The following guidelines are adaptations of recommendations for people infected with human immunodeficiency virus (HIV) and
for other cat owners by the Centers for Disease Control and Prevention and the AAFP to lessen the likelihood of acquiring
Bartonella species infections from cats.19, 29
- If a family member is immunosuppressed and a new cat is to be acquired, adopt a healthy cat older than 1 year.
- Declawing is generally not advised, but immunosuppressed people should avoid cat bites and scratches.
- Cat-associated wounds should be washed promptly and medical advice sought.
- Cats should not be allowed to lick open wounds on immunosuppressed people.
- Flea control should be maintained.