Cyclic CD8+lymphopenia in dogs experimentally infected with Bartonella vinsonii subsp berkhoffii

Until recently, it was presumed that Bartonella vinsonii only infected vole s, a species of North American rodents. In April of 1993, however, our labo ratory isolated a novel subspecies of B. vinsonii (B. vinsonii subsp. berkh offii) from the blood of a dog diagnosed with vegetative valvular endocardi tis. Subsequently, based on a seroepidemiologic survey of dogs from North C arolina and Virginia presenting for a variety of medical problems, we found evidence supporting a potentially important association between B. vinsoni i and Ehrlichia canis co-infection in dogs. In the following study, eight d ogs were infected with B. vinsonii: four specific pathogen free dogs and fo ur dogs that had previously been infected with E. canis. Flow cytometric an alysis of peripheral blood lymphocytes revealed a cyclic elevation of the C D4/CD8 T-cell ratio that correlated with cyclic CD8+ lymphopenia in all dog s infected with B. vinsonii, regardless of prior exposure to E. canis. (C) 2000 Elsevier Science B.V. All rights reserved.