Small Animal - Infectious Disease

INTRODUCTION Historically, studies from our research group have involved intracellular pathogens in the Genera Babesia, Ehrlichia, Rickettsia, and more recently, Bartonella. In regard to the study of these obligate intracellular or in the case of Bartonella sp., highly fastidious pathogens, clinical, as well as more basic research initiatives, have been hampered by difficulties associated with the in vitro culture of these organisms. The advent of molecular techniques that facilitate the detection of bacterial DNA in a patient blood sample has begun to revolutionize the current understanding and medical practices related to the management of infectious diseases. To a substantial degree, this molecular diagnostic revolution started with investigations related to Bartonella sp. Although predated by a substantial number of important observations, three manuscripts, published in the New England Journal of Medicine in 1990, set the stage for a scientific revolution in our understanding of Bartonella infections. Relman and colleagues used polymerase chain reaction (PCR) to amplify bacterial DNA from lesions of AIDS patients with bacillary angiomatosis. For nearly a decade prior to the use of this approach, pathologists had observed “unculturable” silver-staining bacteria in bacillary angiomatosis lesions. When compared with known eubacterial sequences, the uncultured organisms were most closely related to Rochalimaea quintana, the cause of Trench Fever. Perkocha, a human pathologist, and his colleagues reported concurrently that “unculturable“ Warthin-Starry staining bacilli could be found in patients with peliosis hepatis, a rare hepatic lesion seen in people with chronic wasting diseases such as pulmonary tuberculosis, advanced cancer or HIV infection. Independently, Slater and colleagues described the isolation of a novel, fastidious gram-negative organism in blood cultures from immunocompromised and nonimmunocompromised febrile patients. The organisms described in these three manuscripts were all subsequently characterized as B. quintana or B. henselae, which was defined as a new species in 1992. During the ensuing 10 years, research efforts have begun to elucidate the importance of Bartonella species as both veterinary and human pathogens. More importantly, the potential utility of a new technique for the specific identification of bacteria in patient samples was introduced to the medical professions. We now know that a variety of Bartonella spp. can infect cats, dogs, mice, men and a variety of other mammalian species.