What is ehrlichiosis?

Ehrlichiosis is a group of infections caused by several forms of the bacterium Ehrlichia. Ticks transmit the bacteriaum (and other infections such as Rocky Mountain spotted fever or Lyme disease) to humans through bites on the skin. Without treatment, this infection may cause serious complications. However, ehrlichiosis does not become a chronic (ongoing) condition.

Who is likely to have ehrlichiosis?

You may develop ehrlichiosis if you live in a region with disease-carrying ticks. These ticks live primarily in the central and southeastern United States. Cases of ehrlichiosis are also reported in Wisconsin and Minnesota.

How does one contract ehrlichiosis?

Ehrlichiosis results from the bite of a tick carrying one of the forms of Ehrlichia bacteria. Many types of ticks, Lone star ticks, deer ticks, and dog ticks can carry ehrlichia bacterium. Blacklegged ticks also spread the infection.

Rarely, blood transfusions or organ transplants infected with the bacterium have caused ehrlichiosis.

Symptoms and Causes

What are the symptoms of ehrlichiosis?

Symptoms often appear a week or more after an infected tick bites a person. The symptoms vary from person to person and range from mild to severe. If untreated, the symptoms and infection may last for weeks. Most commonly, symptoms of ehrlichiosis include:

  • Flu-like symptoms, such as fever, chills, muscle aches, fatigue and sometimes a rash
  • Diarrhea, nausea, vomiting, not being hungry
  • Headache and confusion
  • Red eyes (more often in children)

A generalized rash is uncommon and occurs in a minority of cases, but more often in children than adults. If present, additional infections or conditions should also be considered.

In people with other significant health problems, or if the infection is not treated, the symptoms and illness may be more severe. In severe cases, ehrlichiosis may cause:

  • Seizure
  • Coma
  • Difficulty breathing
  • Organ failure
  • Other infections (superinfections) from viruses or fungi, which may require additional more specific treatment

Diagnosis and Tests

How is ehrlichiosis diagnosed?

Your doctor diagnoses ehrlichiosis with a careful history and physical examination asking about tick exposure, tick bites or maybe the rash. Blood tests to confirm the presence of the bacterium causing ehrlichiosis and other lab abnormalities may be necessary such as blood counts and liver tests.

Management and Treatment

How is ehrlichiosis treated?

Ehrlichiosis treated with the antibiotics, usually doxycycline. This antibiotic is effective for both adults and children. Symptoms usually improve rapidly in the first few days.

In more severe cases, intravenous (IV) antibiotics are administered at a hospital until symptoms improve.

The infection is fatal in 2-5% of people who do not receive timely treatment. Deaths happen most often among children younger than 10 years old and adults aged 70 or older. People with weak immune systems or other serious health problems are more likely to have severe symptoms.


Can ehrlichiosis be prevented?

Preventing tick bites is the best way to prevent ehrlichiosis. Tick bites are best prevented by:

  • Avoiding areas where ticks are present, such as woods with thick ground cover and by staying on open cleared trails.
  • Wearing light colored long sleeved shirts and tucking pant legs into your boots.
  • Treating your clothing and outdoor gear with protective chemicals, like permethrin.
  • Using insect repellants containing DEET.

When you come indoors after spending time in nature — or even in grassy areas of your own yard — you should:

  • Check your body and clothing for ticks.
  • Shower soon after returning inside.
  • Check any outdoor pets or equipment for ticks.

Outlook / Prognosis

What is the prognosis (outlook) for people with ehrlichiosis?

Most people with ehrlichiosis respond well to treatment with doxycycline and recovery fully from their symptoms.

Living With

When should I call my doctor about ehrlichiosis?

If you have any symptoms of ehrlichiosis, or find a tick attached to your body after camping, hiking, or walking outdoors in an area where ticks are present, contact your doctor for advice and a possible evaluation.

Last reviewed by a Cleveland Clinic medical professional on 08/16/2019.


  • American Academy of Pediatrics. Sick from Ticks: Human Ehrlichiosis. ( Accessed 8/20/2019.
  • American Lyme Disease Foundation. Ehrlichiosis. ( Accessed 8/20/2019.
  • Centers for Disease Control and Prevention. Ehrlichiosis. ( Accessed 8/20/2019.
  • Centers for Disease Control and Prevention. Preventing tick bites. ( Accessed 8/20/2019.
  • Merck Manual Professional Version. Ehrlichiosis and anaplasmosis. ( Accessed 8/20/2019.

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