Ehrlichia chaffeensis is a zoonotic, pathogenic bacterium. All Erlichiae are cocci and gram negative. Ehrlichia chaffeensis is obligately intracellular and cycles mainly through the tick/deer cycle. It can infect humans and causes human monocytic ehrlichiosis, transmitted normally through the bite of an adult Lone Star Tick. These ticks live through the south of the United States.
Human monocytic ehrlichiosis attacks the white blood cells. There, Ehrlichia chaffeensis form vacuole-bound colonies known as morulae. These are hallmark of the Erlichiae diseases. The name is interesting as morulae is plural for morula which is the Latin word for mulberry. The big dividing lumps of these organisms are arranged like mulberries.
I find this particular bacterium interesting because of the difficulty culturing it. There appear to be many Erlichiae found all over the world, but Ehrlichia chaffeensis was the first to be discovered, in 1986, and only because of an atypical case. Still the true impact of the disease is unknown, because the testing is difficult and many physicians are unaware of this disease. Reporting isn’t mandatory in many states. It appears, though, that this disease will only increase, much like incidence of Lyme’s disease has.
Also, the diseases’ main presenting symptoms are a fever and headache, which are not exactly the most narrow of complaints from a patient. Presenting patients have a mild to severe illness and the effective treatment is tetracycline. This disease can be fatal, with a higher morbidity incidence in children and, possibly, the immunocompromised.
Knowledge of this pathogen is extremely scant. It is hard to culture, so it is difficult both to diagnose and research. There have been reports of the disease from the United States to Israel (though some scientists question those making the claims).
ResourcesThe CDC website www.cdc.gov
More specifically http://www.cdc.gov/ncidod/dvrd/ehrlichia/Index.htmDumler, et al. Human Monocytic Ehrlichiosis: A Potentially Severe Disease in Children The
Pediatric Forum, 2000. http://archpedi.ama-assn.org/issues/v154n8/ffull/plt0800-1.htmlWalker, D.H. & Dumler, J.S. Emergence of the ehrlichioses as human health problems
Emerging Infectious Diseases, 1996. pg 18-29
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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