Infection is via the transfer of infected blood by fleas and other biting insects from cat to cat. The hemobartonella then attach to the surface of RBCs where they multiply and spread to other RBCs. These infected cells are bound up by macrophages (defensive white blood cells) in the spleen effectively removing them from the circulation resulting in anemia (low RBCs). The time from infection to onset of signs is around two weeks. Bouts of recurring clinical signs then last for one to two months as the hemobartonella go through cycles of replication. Eventually surviving cats develop adequate immunity to the parasite and overcome the anemia.

Clinical signs include weight loss, anemia, weakness and depression. Jaundice (yellow gums) may be seen in some cats. Mortality (death) rates can reach 30% in untreated cats. Many recovered cats will continue to harbor the hemobartonella acting as carriers for infection of other cats.

Treatment with Tetracyclines will help to accelerate recovery however does not prevent development of carriers states. Corticosteroids are also used to reduce to rate at which the macrophages bind RBCs in the spleen.