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Category: Clinical Microbiology
Human Monocytotropic Ehrlichiosis, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816490/9781555812386_Chap14-1.gif /docserver/preview/fulltext/10.1128/9781555816490/9781555812386_Chap14-2.gifAbstract:
This chapter first gives a brief history of human monocytotropic ehrlichiosis (HME), which is a zoonotic disease. From this brief history of HME, it is clear that rapid progress in understanding this newly emerged tick-borne zoonosis was facilitated both by its successful cultivation and by experimental studies of ticks linked to field observations. Epidemiological studies were furthered through the use of molecular techniques, and knowledge of HME expanded rapidly in the early to mid-1990s. Next, the chapter talks about biology of the etiologic agent. In the eastern United States, Ehrlichia chaffeensis is maintained in an epizootic cycle involving the lone star tick (Amblyomma americanum) as the principal vector and the white-tailed deer (Odocoileus virginianus) as a major vertebrate reservoir. This critical vector-host association places these two species at the core of E. chaffeensis epizootiology and strongly influences its geographic distribution and seasonality of transmission. HME caused by E. chaffeensis is endemic to the United States, with residents in the southeastern and south-central states at highest risk. The clinical recognition of HME can be difficult, since the spectrum of manifestations is broad and nonspecific, ranging from asymptomatic infection to mild self-limited symptoms to rapidly fatal disease. HME typically presents as an uncomplicated, acute, nonspecific febrile illness that resolves rapidly if treated with doxycycline, characteristic of many rickettsial infections. The chapter ends with a discussion on laboratory diagnosis, treatment and prevention of HME.
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Electron micrograph of E. chaffeensis in the cytoplasm of a macrophage. Photograph appears courtesy of Cynthia Goldsmith (CDC).
Electron micrograph of E. chaffeensis in the cytoplasm of a macrophage. Photograph appears courtesy of Cynthia Goldsmith (CDC).
Average annual incidence of HME through 2001, as derived from states reporting cases. The legend indicates incidence values stratified into quartiles.
Average annual incidence of HME through 2001, as derived from states reporting cases. The legend indicates incidence values stratified into quartiles.
(a) The average age-specific incidence of HME derived from states reporting cases; (b) month of onset for HME.
(a) The average age-specific incidence of HME derived from states reporting cases; (b) month of onset for HME.