Ehrlichiosis and Lyme Disease: Symptoms and Treatment
Ehrlichiosis—like its close relative Anaplasmosis—can turn a typical Lyme disease presentation into a severe acute illness requiring immediate recognition and treatment. The same ticks that transmit Lyme disease also carry Ehrlichia bacteria, creating coinfections that produce high fever, severe headache, and dangerous blood count abnormalities. For a complete overview of tick-borne coinfections, see the Lyme disease coinfections guide.
Ehrlichiosis affects approximately 3–5% of Lyme disease patients in endemic areas, though cases are frequently missed or misdiagnosed as viral illness. The infection presents acutely, often within the first week or two after tick bite, with symptoms severe enough to require hospitalization when diagnosis and treatment are delayed.
What Is Ehrlichiosis?
Ehrlichiosis is a bacterial tick-borne infection caused primarily by Ehrlichia chaffeensis. It is transmitted mainly by the lone star tick and can cause high fever, severe headache, muscle aches, and characteristic blood count abnormalities.
Ehrlichiosis is caused by Ehrlichia species bacteria—primarily Ehrlichia chaffeensis and Ehrlichia ewingii in the United States—transmitted by the lone star tick and potentially other tick species.
Ehrlichiosis Symptoms
Ehrlichiosis presents as acute illness with rapid onset of severe symptoms. The characteristic clinical picture includes high fever (often 102–104°F), severe headache, profound muscle aches, nausea and vomiting, and malaise disproportionate to physical findings. Confusion or altered mental status may occur in severe cases.
Common Ehrlichiosis Symptoms in Humans
- High fever and chills
- Severe headache
- Profound muscle aches
- Fatigue and malaise
- Nausea and vomiting
- Loss of appetite
- Confusion or altered mental status in severe cases
- Rash, particularly in children
Symptoms usually begin 1 to 2 weeks after a tick bite and may worsen rapidly if treatment is delayed.
Unlike Lyme disease’s erythema migrans rash, Ehrlichiosis may produce a nonspecific rash in 30–40% of patients—particularly children—that appears as small red spots or petechiae.
Characteristic Laboratory Findings
Ehrlichiosis often produces distinctive laboratory abnormalities that help distinguish it from viral illnesses.
- Low white blood cell count (leukopenia)
- Low platelet count (thrombocytopenia)
- Elevated liver enzymes
- Low sodium levels (hyponatremia)
The combination of acute fever and these laboratory findings should raise suspicion for Ehrlichiosis.
Ehrlichiosis vs. Anaplasmosis
Ehrlichiosis and Anaplasmosis are closely related infections with overlapping symptoms and similar laboratory findings. Both respond to doxycycline and are frequently misdiagnosed as viral illness.
Why Ehrlichiosis Is Missed
Ehrlichiosis is frequently dismissed as influenza or other viral infections because the symptoms overlap considerably.
Testing limitations contribute to missed diagnoses. Ehrlichia serology may be negative early in the illness, and PCR testing is not universally available.
Ehrlichiosis and Lyme Disease Coinfection
Geographic overlap means Ehrlichiosis and Lyme disease coinfection can occur. Fortunately, doxycycline treats both infections.
How Common Is Ehrlichiosis?
Ehrlichiosis remains less common than Lyme disease, but reported cases have increased steadily in recent years. The infection is most common in the southeastern, south-central, and mid-Atlantic United States where lone star ticks are abundant.
Reported cases have risen substantially over the last two decades as lone star ticks have expanded their geographic range.
How Is Ehrlichiosis Treated?
Doxycycline is the treatment of choice for Ehrlichiosis. Most patients improve within 24 to 48 hours after starting therapy, and treatment should begin as soon as the disease is suspected.
Because delays increase the risk of severe complications, clinicians often begin treatment before confirmatory laboratory results are available.
Treatment and Complications
Standard treatment is doxycycline 100 mg twice daily for 10–14 days.
Delayed treatment can lead to respiratory failure, kidney injury, neurologic complications, bleeding disorders, septic shock, and death in rare cases.
Can Ehrlichiosis Cause Long-Term Problems?
Most patients recover completely when treatment begins promptly. Delayed diagnosis or severe illness may increase the risk of prolonged fatigue, weakness, or lingering symptoms.
Frequently Asked Questions
What is Ehrlichiosis?
Ehrlichiosis is a bacterial tick-borne infection caused primarily by Ehrlichia chaffeensis.
What are the main symptoms of Ehrlichiosis?
High fever, severe headache, profound muscle aches, nausea, and fatigue are common symptoms.
How is Ehrlichiosis different from Lyme disease?
Ehrlichiosis causes acute febrile illness with characteristic blood count abnormalities and often presents more abruptly than Lyme disease.
Can you have Ehrlichiosis and Lyme disease together?
Yes. Coinfection can occur, and doxycycline treats both infections.
How common is Ehrlichiosis?
Reported cases have increased steadily in recent years, especially in areas where lone star ticks are common.
How is Ehrlichiosis treated?
Doxycycline remains the treatment of choice.
Can Ehrlichiosis cause long-term problems?
Most patients recover completely, although delayed diagnosis may increase the risk of lingering symptoms.
What laboratory abnormalities are seen with Ehrlichiosis?
Common findings include low white blood cells, low platelets, elevated liver enzymes, and hyponatremia.
Clinical Takeaway
Ehrlichiosis is an acute bacterial tick-borne infection characterized by high fever, severe headache, and characteristic laboratory abnormalities.
When acute febrile illness occurs after tick exposure, empiric doxycycline treatment should begin promptly rather than waiting for confirmatory laboratory testing.
Related Articles
Lyme Disease Coinfections Guide
Lyme Test Accuracy
Persistent Lyme Disease Overview
Recovery From Lyme Disease
References
- Ismail N, McBride JW. Tick-borne emerging infections: ehrlichiosis and anaplasmosis. Clin Lab Med. 2017;37(2):317-340.
- Paddock CD, Childs JE. Ehrlichia chaffeensis: a prototypical emerging pathogen. Clin Microbiol Rev. 2003;16(1):37-64.
- Biggs HM, Behravesh CB, Bradley KK, et al. Diagnosis and management of tickborne rickettsial diseases. MMWR Recomm Rep. 2016;65(2):1-44.
- Centers for Disease Control and Prevention. Ehrlichiosis.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
