Emergent opportunities in humans: playful kittens, an arthropod vector, and a zoonotic agent

Bartonella henselae is implicated as the main etiologic agent of Cat scratch disease (CSD, Cat-scratch fever). A majority of domestic cats may harbor the intra-erythrocytic agent for extended periods without apparent disease. In humans, B. henselae most commonly results in a subacute, bacterial infection that presents with one or more reddish papules which may progress to pustules and regional lymph node enlargement. Usual features include fever, malaise, and a granulomatous lymphadenitis on biopsy. However, atypical clinical presentations occur, albeit with infrequence, and may result in a difficult and protracted diagnostic process. The infection in susceptible hosts such as immunocompromised or elderly patients may result in endocarditis, encephalitis, fever of unknown origin, and general malaise. It is not transmitted from person to person and quarantine is not necessary. The arthropod vector, Ctenocephalides felis, or the cat flea, plays a major role in transmission among cats and to humans. The transmission risk to humans can be substantially reduced through elimination of flea infestations in companion animals. There are numerous recent reviews and case reports in the veterinary and medical literature reflecting increased recognition of this zoonotic agent. All this notwithstanding, many physicians and other providers may not be familiar with this agent and the potential spectrum of human disease; this may lead to delays in diagnosis and unnecessary diagnostic procedures. This article emphasizes the aspects of B. henselae infection, including a typical case report and a table with selected human case reports of unusual clinical manifestations from the published literature.