Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/1994
Publication Date: N/A
Interpretive Summary: There are two species of rickettsia (bacteria-like organisms) that invade t red blood cells and cause disease in domestic ruminants (sheep and cattle). The organisms can be spread in several ways, but ticks are the primary natu means. The two species that infect domestic sheep and cattle respectively, are Anaplasma ovis and Anaplasma marginale. While the disease has been wel lstudied in domestic animals, less is known about their association with wi ruminants. Since both wild and domestic ruminants often share habitat, especially in the western U.S., it is important to understand the role of t wild ruminant in the overall dynamics of the disease. In this study, we ha shown that North American elk are susceptible to infection with both specie but more so with Anaplasma marginale. Healthy elk appear to be able to mou a successful immune response to infection with either organism; they did no develop severe clinical disease when infected. However, Anaplasma marginal lreproduced to higher levels than Anaplasma ovis, and are thus the likely organisms found in naturally infected elk. The study was important in understanding the role that these wild animals play in the disease transmission in nature. The data from this study, and others will provide basis for the development of a comprehensive computer model of the disease that can be used to predict the effects of various control strategies.
Technical Abstract: Anaplasma ovis was experimentally transmitted from domestic sheep to elk (Cervus elaphus) and back to splenectomized sheep. No rickettsemias were detected but serum from 3 of 7 experimentally inoculated elk developed Anaplasma-reactive antibody as measured by indirect immunofluorescence or by the rapid card agglutination and complement-fixation assays. Four elk were experimentally infected with A. marginale. The rickettsia were detected in blood of these elk and caused disease in splenectomized domestic bovine calf after subinoculation of blood from the elk. No clinical signs of illness were noted in any elk inoculated with either Anaplasma species. Elk are susceptible to infection with both Anaplasma species and could contribute to the epidemiology of both.