Cyclic Thrombocytopenia Induced by a Rickettsia-Like Agent in Dogs

Abstract

Hematologic manifestations and the ultrastructure of a platelet-specific microorganism isolated from a dog in Florida were studied. The agent was readily transmitted experimentally to adult dogs by intravenous inoculation with infected blood. Parasitemias and concomitant thrombocytopenias were cyclic in that both recurred within relatively constant periods of one to two weeks following experimental infections. Hemorrhage was not a manifestation of the disease even though thrombocytopenias were severe. Microorganisms were visualized by light and electron microscopy. They were observed only in platelets and were composed of single or multiple subunits (morula forms). The microorganisms were ultrastructurally very similar to those reported in Ehrlichia canis infections of dogs and Anaplasma marginale infections of cattle. Microorganisms were surrounded by single membranes which more or less conformed to the external surfaces of subunits that were surrounded by double membranes. From electron microscopic studies, it is suggested that these organisms be classified in the order Rickettsiales.

Evaluation of blood and bone marrow in selected canine vector-borne diseases

“…Erythrophagocytosis may also occur as an "innocent bystander effect" whereby phagocytic macrophages remove red cells in the process of removing cellular debris, such as in the case of disseminated fungal infection [35], lymphocytic leukemia, myelomonocytic leukemia [36] and BM necrosis [37]. Erythrophagocytosis and platelet phagocytosis were observed in four A. platys infected dogs ( Figure 4A,B), consistent with the immunemediated thrombocytopenia that this pathogen is known to induce [38,39].…”

Isolation of anAnaplasmasp. Organism from White-Tailed Deer by Tick Cell Culture

“…Not all of them have not been isolated in culture but have been detected through immunologic and molecular means. One of these, i.e., E. ewingii, also infects dogs and/or humans (1,8,9,22,25,27,43,49,59), but a second one, termed WTD agent (7,14,38), which is closely related to, but not identical with, A. platys (27,43), has thus far been detected only in cervids (WTD as well as possibly mule deer and black-tailed deer [21]). The public or veterinary health importance of this agent has not been determined.…”

The Biological Survey of Canada: A Personal History

“…Anaplasma platys Dumler et al (Rickettsiales: Ehrlichiaceae), which causes canine infectious cyclic thrombocytopenia was first reported in the United States of America in 1978 (Harvey et al 1978) and is enzootic in many parts of the United States of America. Anaplasma platys appears to parasitise platelets of dogs only and is thought to be transmitted by the brown dog tick, R. sanguineus (Martin et al 2005).…”