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Definition: ehrlichiosis from Merriam-Webster's Collegiate(R) Dictionary

(1965) : infection with or disease caused by tick-borne bacteria (genus Ehrlichia of the family Anaplasmataceae)

Summary Article: ehr•lich•i•o•sis
From Stedman's Medical Dictionary

(er-lik′ē-ō′sis). Infection with leukocytic rickettsiae of the genus Ehrlichia; in humans, especially by E. sennetsu that produces manifestations similar to those of Rocky Mountain spotted fever.

human ehrlichiosis

a form of ehrlichiosis that presents clinically as an undifferentiated acute febrile illness characterized by fever, chills, diarrhea, and headache, following tick bite(s), probably by the Lone Star tick, Amblyomma americanum. Usually caused by Ehrlichia chaffeensis. First described in 1987. (Thought to be predominantly a monocytic form of ehrlichiosis.) see also human granulocytotropic ehrlichiosis, human monocytotropic ehrlichiosis.

human granulocytotropic ehrlichiosis (HGE)

an acute infectious disease characterized by fever, chills, headache, joint and muscle pains, and sometimes respiratory, gastrointestinal, hepatic, or other systemic involvement; first described in 1994 in northeastern and northern midwestern states and in California. The causative agent, Anaplasma phagocytophilum, is an obligately intracellular organism with a gram-negative cell wall. The deer tick, Ixodes scapularis, is the principal vector, and the peak incidence is in July. Hematologic studies show depression of erythrocytes, leukocytes, and platelets. Clusters of developing organisms called morulae may be seen in neutrophils in stained blood smears, but serologic testing is more sensitive. see human ehrlichiosis, human monocytotropic ehrlichiosis.

human monocytotropic ehrlichiosis (HME)

an acute infectious disease characterized by fever, chills, headache, muscle and joint pain, and variable respiratory, gastrointestinal, and systemic involvement; hematologic studies show depression of erythrocytes, leukocytes, and platelets. The finding of clumps of developing organisms, called morulae, in the cytoplasm of monocytes in a stained smear of peripheral blood establishes the diagnosis, but their detection is often difficult. Serologic testing shows antibody to Ehrlichia chaffeensis, an organism closely resembling the agent of canine ehrlichiosis, E. canis. This disease has been largely confined to the southeastern and south central United States. The Lone Star tick (Amblyomma americanum) and the American dog tick (Dermacentor variabilis) are the principal vectors. Incidence is highest from April to September, during the peak activity of these ticks. see human ehrlichiosis, human granulocytotropic ehrlichiosis.

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