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The lone star tick, which is one of three ticks that can spread Ehrlichiosis. It is characterized by the white dot on its back.[1]
SymptomsFever, headaches, muscle aches, vomiting, diarrhea, confusion, splotchy or pinpoint rash. More severe symptoms include brain or nervous system damage, respiratory failure, bleeding, organ failure[2]
CausesBite from an infected tick
Risk factorsAge, immunocompromised

Ehrlichiosis is a tick-borne infection,[3][4] caused by bacteria of the Ehrlichia and Anaplasma type.

These obligate intracellular bacteria infect and kill white blood cells.

Ehrlichiosis affects about 2.3 per million people a year.[5]

Signs and symptoms

Specific symptoms include fever, chills, severe headaches, muscle aches, nausea, vomiting, diarrhea, loss of appetite, confusion, and a splotchy or pinpoint rash.[6] More severe symptoms include brain or nervous system damage, respiratory failure, uncontrollable bleeding, organ failure, and death. Ehrlichiosis can also blunt the immune system by suppressing production of TNF-alpha, which may lead to opportunistic infections such as candidiasis.

Most of the signs and symptoms of ehrlichiosis can likely be ascribed to the immune dysregulation that it causes. A "toxic shock-like" syndrome is seen in some severe cases of ehrlichiosis. Some cases can present with purpura and in one such case, the organisms were present in such overwhelming numbers that in 1991, Dr. Aileen Marty of the AFIP was able to demonstrate the bacteria in human tissues using standard stains, and later proved that the organisms were indeed Ehrlichia using immunoperoxidase stains.[7]

Experiments in mouse models further support this hypothesis, as mice lacking TNF-alpha I/II receptors are resistant to liver injury caused by Ehrlichia infection.[8]

About 3% of human monocytic ehrlichiosis cases result in death; however, these deaths occur "most commonly in immunosuppressed individuals who develop respiratory distress syndrome, hepatitis, or opportunistic nosocomial infections."[9]


E. sennetsu RC adhere to the cell surface and is being phagocytosed by a cell ruffle

Six species cause human infection:[10]

The latter three infections are not well studied. Ehrlichia muris eauclairensis was recently discovered and has low reporting numbers due to the fact that it is relatively new and because its symptoms are very similar to the symptoms caused by other Ehrlichia bacteria.

In 2008, human infection by a Panola Mountain (in Georgia, USA) Ehrlichia species was reported.[12] On August 3, 2011, infection by a yet-unnamed bacterium in the genus Ehrlichia was reported, carried by deer ticks and causing flu-like symptoms in at least 25 people in Minnesota and Wisconsin. Until then, human ehrlichiosis was thought to be very rare or absent in both states.[13] The new species, which is genetically very similar to an Ehrlichia species found in Eastern Europe and Japan called E. muris, was identified at a Mayo Clinic Health System hospital in Eau Claire.[13]

Ehrlichia species are transported between cells through the host-cell filopodia during the initial stages of infection; whereas, in the final stages of infection, the pathogen ruptures the host cell membrane.[14]


Ixodes scapularis is another type of tick that can spread Ehrlichiosis muris eauclairensis.[11]

The transmission of the bacteria can occur via the following:[15]

  • Tick bites
  • Blood transfusion


In terms of the diagnosis of Ehrlichiosis we find that a blood test is done to ascertain if the individual is infected with this illness[16]


No human vaccine is available for ehrlichiosis. Tick control is the main preventive measure against the disease. However, in late 2012, a breakthrough in the prevention of canine monocytic ehrlichiosis was announced when a vaccine was accidentally discovered by Prof. Shimon Harrus, Dean of the Hebrew University of Jerusalem's Koret School of Veterinary Medicine.[17]

Measures of tick bite prevention include staying out of tall grassy areas that ticks tend to live in, treating clothes and gear that a tick could jump on, using EPA approved bug repellent, tick checks for all humans, animals, and gear that potentially came into contact with a tick, and showering soon after being in an area that ticks might also be in.[18]


Doxycycline and minocycline are the medications of choice. For people allergic to antibiotics of the tetracycline class, rifampin is an alternative.[5] Early clinical experience suggested that chloramphenicol may also be effective, but in vitro susceptibility testing revealed resistance.[citation needed]


Ehrlichiosis is a nationally notifiable disease in the United States. Cases have been reported in every month of the year, but most cases are reported during April–September.[19][20][21] These months are also the peak months for tick activity in the United States.[11] The majority of cases of Ehrlichiosis tend to be in the United States. The states affected most include "the southeastern and south-central United States, from the East Coast extending westward to Texas."[11]

Since the first case of Ehrlichiosis was reported in 2000, cases reported to the CDC have increased, for example, in 2000, 200 cases were reported and in 2019, 2,093 cases were reported. Fortunately, the "proportion of ehrlichiosis patients that died as a result of infection" has gone down since 2000.[11]

From 2008 to 2012, the average yearly incidence of ehrlichiosis was 3.2 cases per million persons. This is more than twice the estimated incidence for 2000–2007.[21] The incidence rate increases with age, with the ages of 60–69 years being the highest age-specific years. Children less than 10 years and adults aged 70 years and older have the highest case-fatality rates.[21] A documented higher risk of death exists among persons who are immunosuppressed.[19]

Other animals

Dogs infected with Ehrlichia often show lameness, lethargy, enlarged lymph nodes, and loss of appetite during the acute phase, which is one to three weeks after infection. Other symptoms include cough, diarrhea, vomiting, abnormal bruising and/or bleeding, fever, and loss of balance.[22]

See also


  1. CDC (2019-01-17). "Ehrlichiosis home | CDC". Centers for Disease Control and Prevention. Archived from the original on 2021-11-01. Retrieved 2021-11-03.
  2. CDC (2019-01-17). "Signs and symptoms of ehrlichiosis | CDC". Centers for Disease Control and Prevention. Archived from the original on 2020-10-30. Retrieved 2021-11-03.
  3. "Ehrlichiosis". Division of Vector-Borne Diseases (DVBD), National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Centers for Disease Control and Prevention. 15 November 2013. Archived from the original on 1 October 2018. Retrieved 27 February 2023.
  4. Dawson, Jacqueline E.; Marty, Aileen M. (1997). "Ehrlichiosis". In Horsburgh, C.R.; Nelson, A.M. (eds.). Pathology of emerging Infections. Vol. 1. American Society for Microbiology Press. ISBN 1555811205.
  5. 5.0 5.1 5.2 Goddard J (September 1, 2008). "What Is New With Ehrlichiosis?". Infections in Medicine.
  6. Baker, Meghan; Yokoe, Deborah S.; Stelling, John; Kaganov, Rebecca E.; Letourneau, Alyssa R.; O'Brien, Thomas; Kulldorff, Martin; Babalola, Damilola; Barrett, Craig; Drees, Marci; Platt, Richard (2015). "Automated Outbreak Detection of Hospital-Associated Infections". Open Forum Infectious Diseases. 2 (suppl_1). doi:10.1093/ofid/ofv131.60. ISSN 2328-8957.
  7. Marty AM, Dumler JS, Imes G, Brusman HP, Smrkovski LL, Frisman DM (August 1995). "Ehrlichiosis mimicking thrombotic thrombocytopenic purpura. Case report and pathological correlation". Hum. Pathol. 26 (8): 920–5. doi:10.1016/0046-8177(95)90017-9. PMID 7635455.
  8. McBride JW, Walker DH (2011). "Molecular and cellular pathobiology of Ehrlichia infection: targets for new therapeutics and immunomodulation strategies". Expert Rev Mol Med. 13: e3. doi:10.1017/S1462399410001730. PMC 3767467. PMID 21276277.
  9. Thomas, Rachael J; Dumler, J Stephen; Carlyon, Jason A (1 August 2009). "Current management of human granulocytic anaplasmosis, human monocytic ehrlichiosis and ehrlichiosis". Expert Review of Anti-infective Therapy. 7 (6): 709–722. doi:10.1586/eri.09.44. PMC 2739015. PMID 19681699.
  10. Dumler JS, Madigan JE, Pusterla N, Bakken JS (July 2007). "Ehrlichioses in humans: epidemiology, clinical presentation, diagnosis, and treatment". Clin. Infect. Dis. 45 (Suppl 1): S45–51. doi:10.1086/518146. PMID 17582569.
  11. 11.0 11.1 11.2 11.3 11.4 CDC (2021-08-04). "Ehrlichiosis epidemiology and statistics | CDC". Centers for Disease Control and Prevention. Archived from the original on 2021-03-19. Retrieved 2021-11-03.
  12. Reeves WK, Loftis AD, Nicholson WL, Czarkowski AG (2008). "The first report of human illness associated with the Panola Mountain Ehrlichia species: a case report". Journal of Medical Case Reports. 2: 139. doi:10.1186/1752-1947-2-139. PMC 2396651. PMID 18447934.
  13. 13.0 13.1 Steenhuysen, J. (3 August 2011). "New tick-borne bacterium found in upper Midwest". Reuters. Archived from the original on 2012-06-09.
  14. Thomas S, Popov VL, Walker DH (2010). Kaushal D (ed.). "Exit Mechanisms of the Intracellular Bacterium Ehrlichia". PLOS ONE. 5 (12): e15775. Bibcode:2010PLoSO...515775T. doi:10.1371/journal.pone.0015775. PMC 3004962. PMID 21187937.
  15. "Transmission of the bacteria which cause ehrlichiosis | CDC". Centers for Disease Control and Prevention. 17 January 2019. Archived from the original on 29 November 2022. Retrieved 11 May 2023.
  16. "Diagnosis and testing of ehrlichiosis | CDC". Centers for Disease Control and Prevention. 17 January 2019. Archived from the original on 30 September 2022. Retrieved 11 May 2023.
  17. Rudoler N, Baneth G, Eyal O, van Straten M, Harrus S (December 2012). "Evaluation of an attenuated strain of Ehrlichia canis as a vaccine for canine monocytic ehrlichiosis". Vaccine. 31 (1): 226–33. doi:10.1016/j.vaccine.2012.10.003. PMID 23072894.
  18. CDC (2020-07-01). "Preventing tick bites on people | CDC". Centers for Disease Control and Prevention. Archived from the original on 2021-07-29. Retrieved 2021-12-02.
  19. 19.0 19.1 Dahlgren FS, Heitman KN, Drexler NA, Massung RF, Behravesh CB. "Human granulocytic anaplasmosis in the United States from 2008 to 2012: a summary of national surveillance data". Am J Trop Med Hyg 2015;93:66–72. Archived 2021-11-12 at
  20. Drexler, Naomi A.; Dahlgren, F. Scott; Heitman, Kristen Nichols; Massung, Robert F.; Paddock, Christopher D.; Behravesh, Casey Barton (2016-01-06). "National Surveillance of Spotted Fever Group Rickettsioses in the United States, 2008-2012". The American Journal of Tropical Medicine and Hygiene. 94 (1): 26–34. doi:10.4269/ajtmh.15-0472. ISSN 1476-1645. PMC 4710440. PMID 26324732. Archived from the original on 2023-02-27. Retrieved 2023-02-27.
  21. 21.0 21.1 21.2 Nichols Heitman, Kristen; Dahlgren, F. Scott; Drexler, Naomi A.; Massung, Robert F.; Behravesh, Casey Barton (2016-01-06). "Increasing Incidence of Ehrlichiosis in the United States: A Summary of National Surveillance of Ehrlichia chaffeensis and Ehrlichia ewingii Infections in the United States, 2008-2012". The American Journal of Tropical Medicine and Hygiene. 94 (1): 52–60. doi:10.4269/ajtmh.15-0540. ISSN 1476-1645. PMC 4710445. PMID 26621561. Archived from the original on 2023-02-14. Retrieved 2023-02-27.
  22. "Ehrlichiosis in Dogs". Pet MD. Archived from the original on 24 January 2023. Retrieved 24 January 2023.

External links

External resources