Ehrlichiosis: Symptoms and Treatment

Quick answer

Ehrlichiosis is a bacterial infection spread mainly by the lone star tick, most often reported in south-central, southeastern and mid-Atlantic states. Symptoms usually start 1 to 2 weeks after a bite: fever, chills, headache, muscle aches and sometimes an upset stomach or rash. CDC says doxycycline is the treatment of choice for all ages.

What is ehrlichiosis?

Ehrlichiosis is a group of infections caused by Ehrlichia bacteria. CDC describes which tick spreads each type and where:

The lone star tick does not spread Lyme disease, according to CDC. So for most people, ehrlichiosis is not a same-bite Lyme co-infection. The exception is E. muris eauclairensis, which is carried by the blacklegged tick in the upper Midwest. The IDSA/AAN/ACR Lyme guideline notes that suspected co-infection with it would call for doxycycline. See all Lyme disease co-infections.

Ehrlichiosis symptoms

Symptoms usually start 1 to 2 weeks after an infected tick bite. Tick bites can be painless, and many people don’t remember one.

Early illness (first 5 days) is usually mild or moderate. CDC lists:

• Fever and chills
• Severe headache
• Muscle aches
• Nausea, vomiting, diarrhea or loss of appetite
• Confusion

Rash: up to 1 in 3 people with ehrlichiosis report a rash, and it is more common with E. chaffeensis. CDC’s clinician page says rash develops in up to 60% of children but fewer than 30% of adults, usually about 5 days after the fever starts. It may look like red splotches or pinpoint dots.

Severe illness can happen, especially when antibiotics are delayed. CDC lists brain and nervous system problems (such as meningoencephalitis), respiratory failure, uncontrolled bleeding, organ failure and death.

Who is at higher risk of severe illness

• People whose antibiotic treatment is delayed
• Children younger than 5 and adults older than 65
• People with weakened immune systems, such as those getting certain cancer treatments, people with advanced HIV, organ transplant recipients, and people taking certain medicines

How ehrlichiosis is diagnosed

CDC notes ehrlichiosis is hard to diagnose early, and severe cases can look like other serious illnesses. Tests may include:

• Blood counts and liver tests. Low white cells, low platelets and moderately raised liver enzymes are common. Normal early results do not rule it out.
• PCR on whole blood. Most sensitive in the first week; it becomes less sensitive within 48 hours of starting antibiotics. A negative result does not rule out ehrlichiosis.
• Paired antibody tests. A rise in antibodies between a sample taken in the first two weeks and one taken 2 to 10 weeks later is the best evidence. A single early test is often negative, and tests can cross-react with Anaplasma.
• Blood smear. Clusters of bacteria (morulae) inside white blood cells strongly suggest infection if seen, but the test is not sensitive enough to use alone.

Ehrlichiosis treatment

We don’t give doses or personal advice. CDC’s guidance for clinicians says:

• Doxycycline is the treatment of choice for all ages, including young children.
• Treatment should start as soon as ehrlichiosis is suspected, without waiting for test results.
• Your provider decides how long treatment lasts, based on how quickly you improve. Fever typically settles within 24 to 48 hours.
• If you are not getting better on doxycycline, CDC says the illness may not be ehrlichiosis. Tell your provider.
• CDC does not recommend antibiotics after a tick bite to prevent ehrlichiosis. See a provider if fever, rash, headache or other symptoms develop within 2 weeks of a bite.

Preventing ehrlichiosis

There is no vaccine. CDC recommends avoiding tick bites, controlling ticks on pets and reducing ticks in your yard. The lone star tick is found mainly in the south-central and eastern U.S., CDC says; learn how to spot it on our lone star tick page. Lone star tick bites are also linked to alpha-gal syndrome. Related infections: anaplasmosis, spotted fever rickettsiosis, and other ticks to know.

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