Haemobartonella felis: recent developments in diagnosis and treatment

Haemobartonella felis is a pleomorphic uncultivated wall-less haemotrophic bacterial parasite. Phylogenetic analysis of 16S rRNA gene sequences from a number of isolates of H felis has demonstrated that these bacteria are most closely related to species in the genus Mycoplasma, and Haemobartonella and related organisms are currently being reclassified as Mollicutes. Diagnosis by cytological examination of blood smears has been problematic, but recent molecular studies have led to the development of sensitive polymerase chain reaction (PCR) assays for diagnosis. Such studies have also resulted in the recognition of two distinct strains of H felis, which are divided into different groups based on phylogenetic analysis. This evolutionary divergence between strains is accompanied by differences in pathogenecity. This review discusses new developments in the diagnosis and treatment of H felis, focusing on the use of, and interpretation of, PCR assays.