About Ehrlichiosis
Ehrlichiosis is caused by Ehrlichia bacteria that live inside white blood cells. In the United States the main cause is Ehrlichia chaffeensis, with smaller numbers from Ehrlichia ewingii. Both spread through the bite of the lone star tick (Amblyomma americanum), which is found across the South, Midwest and East Coast and is spreading north. A third species, Ehrlichia muris eauclairensis, is carried by the blacklegged tick and has only been reported in Wisconsin and Minnesota and in people who traveled there. Ehrlichiosis is a close cousin of anaplasmosis, which is caused by a related bacterium carried by the blacklegged tick; the 2 illnesses look alike and are treated the same way.
Most people have a mild or moderate illness, but ehrlichiosis can be severe, with brain involvement in about 1 in 5 severe cases, bleeding problems and organ failure. The CDC says doxycycline is the first-line treatment for adults and children of all ages, and that treatment should never be delayed or withheld while waiting for lab results. Fever usually breaks within 24 to 48 hours of starting it, and that quick response is itself a clue the diagnosis was right. The usual adult dose is 100 mg twice a day for at least 5 to 7 days and until 72 hours after the fever is gone.
Testing is best done with PCR on a blood sample in the first week of illness; antibody tests often turn positive only later, so a negative early test does not rule the infection out. The CDC does not recommend taking antibiotics to prevent ehrlichiosis after a tick bite, and there is no vaccine. Columbia University's Lyme and Tick-Borne Diseases Research Center and Johns Hopkins both list ehrlichiosis among the infections to consider when someone with a tick bite has fever, low platelets or abnormal liver tests.
Common Symptoms of Ehrlichiosis
Recognizing the signs of Ehrlichiosis early can lead to faster diagnosis and better outcomes. Symptoms may vary in severity from person to person. If you or a loved one are experiencing any of the following, consider speaking with a specialist.
- Fever and chills, usually 5 to 14 days after a tick bite
- Severe headache and muscle aches
- Nausea, vomiting, diarrhea or loss of appetite
- A rash, in up to 60% of children but fewer than 30% of adults
- Low white blood cells and platelets, and raised liver enzymes on blood tests
- Confusion or other brain involvement in severe cases
Who Ehrlichiosis Affects
Anyone bitten by an infected tick, most often in states where the lone star tick is common. Severe illness is more likely in children under 5, adults over 65, people with weakened immunity from advanced HIV, chemotherapy or immune-suppressing drugs, and anyone whose treatment is delayed. Ehrlichia has also spread, rarely, through blood transfusion and organ transplant.
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FDA-Approved Treatments for Ehrlichiosis
There is currently 1 FDA-approved medication for Ehrlichiosis. These therapies represent the current standard of care and may be used alongside or compared against investigational treatments in active clinical trials.
Source: openFDA drug labeling data. This list may not include all treatments. Always consult your doctor.
Help Paying for Ehrlichiosis Treatment
Charity funds and drugmaker programs for Ehrlichiosis, checked at the source.
- Vibramycin (Doxycycline) · Generic from many makers
Side Effect Explorer
Real-world side effect reports from the FDA Adverse Event Reporting System (FAERS). Includes both FDA-approved drugs and investigational therapies from active clinical trials. Click any drug to see what patients reported.
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Diagnosis and Testing
Tick-borne bacterial infection (Ehrlichia chaffeensis or related species), diagnosed by PCR or antibody tests; not genetic.
Trusted Ehrlichiosis Resources
Reputable organizations and medical references for learning more about Ehrlichiosis, including disease registries, foundation resources, and clinical guidelines.