[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Intracellular and atypical bacteria](https://durgical.com/en/microbiology/groups/intracellular-and-atypical-bacteria/) › Ehrlichia / Anaplasma

[Microbiology](https://durgical.com/en/microbiology/) · [Intracellular and atypical bacteria](https://durgical.com/en/microbiology/groups/intracellular-and-atypical-bacteria/)

# Ehrlichia / Anaplasma

- Bacterium
- Gram-negative
- For completeness

Tick-borne bacteria that live inside white blood cells; they cause fever with low white cells and platelets.

Updated 2026-11-01

Also called: ehrlichiosis, anaplasmosis

## Key points

- Fever after a tick bite + leukopenia + low platelets + high transaminases
- Morulae: Ehrlichia in monocytes, Anaplasma in granulocytes
- Doxycycline, as for other rickettsial diseases

## At a glance

**Gram**
Gram-negative

**Shape**
Small cocci clustered in morulae

**Oxygen**
Obligate intracellular (white blood cells)

**Family**
Anaplasmataceae

**Stain**
Giemsa or Wright on smear: morulae in the cytoplasm

## Morphology

- Morulae: mulberry-like bacterial clusters inside vacuoles
- Ehrlichia chaffeensis in monocytes; Anaplasma phagocytophilum in neutrophils

## Transmission

- Tick bites: Amblyomma americanum (Ehrlichia) and Ixodes (Anaplasma)
- Rarely by transfusion

**Reservoir:** Deer, rodents and other mammals; dogs for some Ehrlichia species

**Vector:** Lone star tick (Amblyomma americanum) and Ixodes

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Virulence factors

- Live in white-cell vacuoles and avoid being killed
- Impair white-cell function and drive systemic inflammation

## Diseases it causes

- Human monocytic ehrlichiosis and human granulocytic anaplasmosis

## Clinical picture

- Fever, chills, severe headache and myalgia one to two weeks after the bite
- Rash is uncommon (more frequent in children with ehrlichiosis)
- Severe forms: respiratory failure, bleeding, multi-organ failure in older or immunosuppressed people

## Diagnosis

- Leukopenia, thrombocytopenia and raised transaminases
- Blood PCR: most useful test in the acute phase
- Morulae on smear (more frequent in anaplasmosis)
- Serology with paired samples

## Treatment

Doxycycline at any age, started on suspicion without waiting for results.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)

## Prevention

- Avoid tick bites: repellents, long clothing, body checks
- Tick control on pets

## Memory aid

Ehrlichia picks the «Monocyte» (think «Ehrlichia: monocytic»); Anaplasma takes the «grAnulocyte», which also carries an A.

## Test yourself

Think of the answer, then tap the question to see it.

## In which cell are Anaplasma phagocytophilum morulae seen?

In neutrophils (granulocytes).

## Which lab findings are typical of ehrlichiosis?

Leukopenia, thrombocytopenia and raised transaminases.

## What is the treatment of choice for ehrlichiosis?

Doxycycline, in adults and children of any age.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/ehrlichia-anaplasma/)

## Related

- [Rickettsia rickettsii / Rickettsia typhi](https://durgical.com/en/microbiology/rickettsia-rickettsii-rickettsia-typhi/)
- [Borrelia burgdorferi](https://durgical.com/en/microbiology/borrelia-burgdorferi/)
- [Orientia tsutsugamushi](https://durgical.com/en/microbiology/orientia-tsutsugamushi/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Intracellular and atypical bacteria](https://durgical.com/en/microbiology/groups/intracellular-and-atypical-bacteria/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [About Ehrlichiosis | Ehrlichiosis | CDC](https://www.cdc.gov/ehrlichiosis/about/index.html) (Centers for Disease Control and Prevention (CDC), 2024); [About Anaplasmosis | Anaplasmosis | CDC](https://www.cdc.gov/anaplasmosis/about/index.html) (Centers for Disease Control and Prevention (CDC), 2024).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/ehrlichia-anaplasma/