527 Users are discussing this topic

PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

See also: Tick-Borne Encephalitis Immunisation written for patients
This page has been archived. It has not been updated since 21/05/2010. External links and references may no longer work.

Ehrlichiosis is a tick-borne infection of mononuclear cells and granulocytes that affects various mammals, including mice, cattle, dogs, deer, horses, sheep, goats, and humans. Ehrlichia are obligate, intracytoplasmic bacteria that resemble Rickettsia and are tiny gram-negative organisms.[1]

  • One of the most common Ehrlichia species infecting humans is Ehrlichia chaffeensis, which mainly infects human monocytes and macrophages (human monocytic ehrlichiosis - HME).
  • Anaplasma phagocytophilum causes human granulocytic anaplasmosis (HGA).
  • Ehrlichia species that infect granulocytes are called human granulocytic ehrlichiosis (HGE).

The clinical manifestations of HME, HGA and HGE are the same.

  • Ehrlichial pathogens are distributed globally, mainly in temperate regions, and have been reported throughout Europe.[2]
  • More common in males than females.
  • Most often occurs in young adults.
  • Elderly patients are more likely to develop severe infections.

NEW - log your activity

  • Notes
    Add notes to any clinical page and create a reflective diary
  • Track
    Automatically track and log every page you have viewed
  • Print
    Print and export a summary to use in your appraisal
Click to find out more »
  • More than 90% of patients give a history of having been bitten by several ticks.
  • Incubation period is 1-4 weeks and infection presents as a febrile illness with headache, malaise, myalgia, arthralgia and rigors.[3]
  • May also have nausea, vomiting and anorexia.
  • Infection may also lead to confusion or a non-specific rash, which can occur anywhere on the body and not necessarily at the site of the tick bite.
  • There are no specific findings on clinical examination but mild hepatomegaly, lymphadenopathy and splenomegaly may occur.
  • Blood count and film: leucopenia, thrombocytopenia.[4] Characteristic morulae (cytoplasmic vacuoles in which the Ehrlichia species grow in peripheral leucocytes) are diagnostic.
  • Mild-to-moderate elevations of aminotransferase levels may be present.[5]
  • An indirect fluorescent antibody test is used for diagnosis. The diagnosis of HME or HGE is made by a single elevated IgG immunofluorescent antibody (IFA) Ehrlichia titre or by demonstrating an increase between acute and convalescent IFA Ehrlichia titres.[1]
  • Polymerase chain reaction technology provides the most sensitive and specific serology testing but this is a research tool and only available in selected hospitals.
  • Doxycycline is very effective in arresting progression of either form of human ehrlichiosis and is continued for 14 days.
  • Rifampin may be useful in patients unable to take doxycycline, eg for children and in pregnancy.
  • The prognosis is excellent in otherwise healthy people with normal immunity.
  • Many cases may be sub-clinical and self-limiting.
  • Wear light-coloured clothes, tuck trousers into socks, use insect repellent.
  • Regularly examine the body for ticks and remove ticks promptly (a feeding period of 3-48 hours is required for the disease to be transmitted).

Further reading & references

  1. Cunha BA; Ehrlichiosis. eMedicine, October 2008.
  2. Strle F; Human granulocytic ehrlichiosis in Europe. Int J Med Microbiol. 2004 Apr;293 Suppl 37:27-35.
  3. Bakken JS, Krueth J, Wilson-Nordskog C, et al; Clinical and laboratory characteristics of human granulocytic ehrlichiosis. JAMA. 1996 Jan 17;275(3):199-205.
  4. Dumler JS, Madigan JE, Pusterla N, et al; Ehrlichioses in humans: epidemiology, clinical presentation, diagnosis, and treatment. Clin Infect Dis. 2007 Jul 15;45 Suppl 1:S45-51.
  5. Walker DH, Dumler JS; Emergence of the ehrlichioses as human health problems. Emerg Infect Dis. 1996 Jan-Mar;2(1):18-29.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Colin Tidy
Current Version:
Document ID:
1447 (v22)
Last Checked:
Next Review:

Did you find this health information useful?

Yes No

Thank you for your feedback!

Subcribe to the Patient newsletter for healthcare and news updates.

We would love to hear your feedback!

Patient Access app - find out more Patient facebook page - Like our page