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Table of Contents

Magill’s Medical Guide, 8th Edition

Ehrlichiosis

by Pam Conboy

Disease/Disorder

Anatomy or system affected: Immune system, musculoskeletal system, nervous system

Specialties and related fields: Family medicine, pediatrics

Definition: Infection by one of a group of intracellular bacteria transmitted to humans through tick bites.

Causes and Symptoms

Human ehrlichiosis is a group of tick-borne bacterial infections caused by Anaplasma phagocytophilum (formerly Ehrlichia phagocytophilum), Ehrlichia chaffeensis, and Ehrlichia ewingii. These bacteria are transmitted by the bite of Ixodes spp. or Amblyomma americanum ticks and subsequently infect circulating white blood cells (leukocytes).

After an incubation period of five to ten days, the disease is typically characterized by fever, chills, and other nonspecific symptoms. A percentage of asymptomatic infections have also been documented. Confirmation of ehrlichiosis infection is accomplished via laboratory methods, including blood-smear examination, polymerase chain reaction, culture, and serologic analysis for the presence of anti-ehrlichia antibodies.

Treatment and Therapy

Ehrlichiosis is effectively treated with a tetracycline antibiotic, most commonly doxycycline. With the increased number of diagnoses, more significant cases requiring hospitalization and condition-appropriate treatment have been documented. Significant complications include respiratory distress, myocarditis, neurological complications, hepatitis, septicemia, and opportunistic infections. Despite clinical similarities between the causative agents, a higher percentage of opportunistic infection has been documented with human granulocytic anaplasmosis (HGA), caused by A. phagocytophilum, whereas increased disease severity and higher mortality has been associated with human monocytic ehrlichiosis (HME), caused by E. chaffeensis. Death resulting from complications may occur in up to 3 percent of cases.

Perspective and Prospects

The reported prevalence and incidence of human ehrlichiosis has been on the rise in regions where specified tick vectors are found. Although historically considered an acute infection conferring long-term immunity, one study found a percentage of HME patients experienced a significantly higher than expected rate of fever, chills, sweats, and fatigue one to three years after the initial illness. Because these symptoms did not correlate with the severity or duration of the initial episode, nor did serological tests confirm the presence of ehrlichia, determination of whether these findings are attributed to a persistent/recurrent infection or a type of postinfection syndrome is still under investigation.

Information on Ehrlichiosis

Causes: Bite of an infected tick

Symptoms: Fever, chills, headache, muscle aches and weakness, joint pain, nausea

Duration: Acute

Treatments: Antibiotics

See also

Bacterial infections; Bacteriology; Bites and stings; Insect-borne diseases; Lice, mites, and ticks; Lyme disease; Parasitic diseases.

For Further Information:

1 

Beltz, Lisa A. “Human Ehrlichiosis.” In Emerging Infectious Diseases: A Guide to Diseases, Causative Agents, and Surveillance, by Lisa A. Beltz. San Francisco: John Wiley & Sons, 2011.

2 

Dumler, J. Stephen. “Anaplasma and Ehrlichia Infection.” Annals of the New York Academy of Sciences 1063 (December, 2005): 361-73.

3 

Dumler, J. Stephen, John E. Madigan, Nicola Pusterla, and Johan S. Bakken. “Ehrlichioses in Humans: Epidemiology, Clinical Presentation, Diagnosis, and Treatment.” Clinical Infectious Diseases 45, suppl. 1 (July 15, 2007): S45-51.

4 

Ganguly, S., and S. K. Mukhopadhayay. “Tick-Borne Ehrlichiosis Infection in Human Beings.” Journal of Vector Borne Diseases 45, no. 4 (December, 2008): 273-80.

5 

Thomas, R. J., J. S. Dumler, and J. A. Carlyon. “Current Management of Human Granulocytic Anaplasmosis, Human Monocytic Ehrlichiosis, and Ehrlichia ewingii Ehrlichiosis.” Expert Review of Anti-Infective Therapy 7, no. 6 (August, 2009): 709-22.

Citation Types

Type
Format
MLA 9th
Conboy, Pam. "Ehrlichiosis." Magill’s Medical Guide, 8th Edition, edited by Bryan C. Auday, et al., Salem Press, 2018. Salem Online, online.salempress.com/articleDetails.do?articleName=MMG2018_0414.
APA 7th
Conboy, P. (2018). Ehrlichiosis. In B. C. Auday, M. A. Buratovich, G. F. Marrocco & P. Moglia (Eds.), Magill’s Medical Guide, 8th Edition. Salem Press. online.salempress.com.
CMOS 17th
Conboy, Pam. "Ehrlichiosis." Edited by Bryan C. Auday, Michael A. Buratovich, Geraldine F. Marrocco & Paul Moglia. Magill’s Medical Guide, 8th Edition. Hackensack: Salem Press, 2018. Accessed December 14, 2025. online.salempress.com.