Update on the Diagnosis and Management of Feline Bartonellosis

Cats have proven by culture or DNA amplification to be infected by Bartonella henselae, B. clarridgeiae, B. koehlerae, B. quintana and B. bovis. Cats are the main reservoir hosts for B. henselae and B. clarridgeiae and are likely to be the reservoir for B. koehlerae. Bartonella henselae is the most common cause of Cat Scratch Disease as well as bacillary angiomatosis, and peliosis hepatis, common disorders in humans with AIDS. Bartonella spp. have intra-endothelial and intra-erythrocytic phases of infection. Based on results of seroprevalence studies, culture, or polymerase chain reaction (PCR) assay, cats are commonly exposed to or infected by Bartonella spp.. The organism is transmitted between cats by Ctenocephalides felis and so prevalence is greatest in cats from regions where fleas are common. In a recent study in the United States, we collected fleas from cats and attempted to amplify Bartonella spp. DNA from flea digests as well as the blood of the cat. The prevalence rates for B. henselae in cats and their fleas were 34.8% and 22.8%, respectively. The prevalence rates for B. clarridgeiae in cats and their fleas were 20.7% and 19.6%, respectively. Results are similar in other studies performed around the world. Bartonella henselae survives in flea feces for days after being passed by infected C. felis. Infected flea feces are likely to contaminate cat claws during grooming and then Bartonella are inoculated into the human when scratched. It is also possible that open wounds are contaminated with infected flea feces.

Most cats with serological evidence of exposure to a Bartonella spp., a Bartonella spp. cultured from blood, or microbial DNA amplified from blood by PCR assay are clinically normal. However, Bartonella spp. infection of cats has also been associated directly or indirectly with a variety of clinical manifestations like fever, lethargy, lymphadenopathy, uveitis, and neurological diseases. How often cats become ill from Bartonella spp. infections is unknown and more information is needed. It is also still also still unclear as to why some cats develop Bartonella associated illness and others do not.

Testing

Blood culture, PCR assay on blood, and serologic testing can be used to assess individual cats for Bartonella infection. Cats that are culture-negative or PCR-negative and antibody-negative and cats that are culturenegative or PCR-negative and antibody-positive are probably not a source of flea, cat, or human infection. However, bacteremia can be intermittent and falsenegative culture or PCR results can occur, limiting the predictive value of a single battery of tests. With PCR, false positive results can occur and positive results do not necessarily indicate that the organism is alive. While serologic testing can be used to determine whether an individual cat has been exposed, both seropositive and seronegative cats can be bacteremic, limiting the diagnostic utility of serologic testing. Thus, testing healthy cats for Bartonella spp. infection is not currently recommended in the United States. Testing should be reserved for cats with suspected clinical bartonellosis. If the results of Bartonella tests are negative in a clinically ill cat, the organism is not likely the cause of the clinical syndrome unless the infection was peracute and serological testing was used as the diagnostic test. If the results of Bartonella tests are positive, the agent remains on the differential list, but other causes of the clinical syndrome must also be excluded. [...]