Bacterial illness
Ehrlichiosis
Ehrlichiosis is a bacterial illness spread to people mainly by the bite of an infected Lone Star tick. It can be treated. It usually causes fever, headache, and body aches. These start about 1–2 weeks after a bite. It responds well to the antibiotic doxycycline when treatment starts early. Most people recover fully with fast care. Delayed treatment is what raises the risk of serious illness. This page is for learning and is not medical advice. Only a licensed doctor can diagnose or treat ehrlichiosis.
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What it is
Ehrlichiosis is the general name for illness caused by Ehrlichia bacteria. In the US, three kinds cause it: E. chaffeensis, E. ewingii, and E. muris eauclairensis. In most of the country, the Lone Star tick (Amblyomma americanum) spreads the first two. In the upper Midwest, the blacklegged tick (Ixodes scapularis) spreads the less common third kind. These germs infect certain white blood cells. This causes a flu-like illness that ranges from mild to severe if it is not treated.
Symptoms
- Fever and chills
- Severe headache
- Muscle aches and general tiredness or feeling unwell (malaise)
- Nausea, vomiting, diarrhea, or loss of appetite
- Confusion in more serious cases
- Rash in about one-third of patients, more often in children than adults. It often appears about 5 days after the fever starts
How soon symptoms appear
Symptoms usually begin about 1–2 weeks (roughly 5–14 days) after the bite of an infected tick, CDC says.
Diagnosis
A doctor diagnoses ehrlichiosis based on your symptoms, recent tick exposure, and where you live or traveled, along with blood tests. Lab results that confirm it can take days to weeks. So doctors often start treatment before results come back when they suspect a tick-borne infection. Routine blood work may show a low white blood cell or platelet count, or high liver enzymes. These can support the diagnosis. You cannot diagnose it yourself.
Treatment
Doxycycline is the treatment of choice for adults and children of all ages. It works best when started early, ideally within the first week of illness. CDC advises not to delay treatment while waiting for lab results if ehrlichiosis is suspected. There is no vaccine. A licensed doctor should make any treatment decision.
Prevention
There is no vaccine, so prevention means avoiding tick bites. Use EPA-registered repellents, such as DEET or picaridin. Treat clothing and gear with permethrin. Avoid tall grass and leaf litter, and walk in the center of trails. Check your whole body for ticks after being outdoors. If a tick is attached, remove it quickly with fine-tipped tweezers, pulling straight out with steady pressure. This lowers your risk of tick-borne illness.
Where it occurs
The two kinds spread by the Lone Star tick are reported most often in the southeastern and south-central US. They are found from the East Coast west to Texas, matching the Lone Star tick's range. The rarer kind, spread by the blacklegged tick, has so far been found only in Wisconsin and Minnesota.
When to seek care
Contact a doctor right away if you get a fever, severe headache, or body aches within a few weeks of a tick bite or time in tick habitat. This matters most in the southeastern or south-central US. Early treatment greatly lowers the risk of severe illness. Get urgent care for warning signs such as confusion, trouble breathing, or unusual bleeding. Young children, adults over 65, and people with weakened immune systems are at higher risk of serious illness. For emergencies such as trouble breathing or anaphylaxis, call emergency services.
Common questions
Which tick spreads ehrlichiosis?
Mainly the Lone Star tick. In most of the US, the Lone Star tick carries Ehrlichia chaffeensis and E. ewingii. In the upper Midwest, the blacklegged tick can spread the rarer E. muris eauclairensis. Note that the Lone Star tick does NOT spread Lyme disease.
Is ehrlichiosis the same as Lyme disease?
No. Different germs cause them, and different ticks spread them. Lyme disease is spread by the blacklegged (deer) tick, not the Lone Star tick. Lyme usually causes a spreading 'bull's-eye' rash. That rash is not a feature of ehrlichiosis.
How is ehrlichiosis treated?
With the antibiotic doxycycline. It is advised for people of all ages and works best when started early. Doctors often start treatment based on symptoms, before test results come back. A licensed doctor should always make treatment decisions.
How soon after a tick bite do symptoms start?
Usually about 1–2 weeks (roughly 5–14 days) after the bite of an infected tick, CDC says.
Does ehrlichiosis always cause a rash?
No. Only about one-third of patients get a rash, and it is more common in children than adults. Not having a rash does not rule out ehrlichiosis, so don't wait for one before you get care.
Sources
- 1.Ehrlichiosis (opens in a new tab) · CDC
Bacterial illness transmitted primarily by the Lone Star tick; treatable with prompt antibiotics.
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This page is here to help you learn. It is not medical advice. Only a doctor can diagnose a tick-borne illness. Read our sources and disclaimer.