After 37 years treating Lyme disease, I’ve seen how Anaplasmosis—a bacterial coinfection transmitted by the same ticks that carry Lyme disease—can transform what appears to be typical Lyme disease into an acute, severe illness with high fever, profound headache, and dangerously low white blood cell counts.
Anaplasmosis occurs in approximately 5-10% of Lyme disease patients in endemic areas, though the true incidence may be higher due to missed diagnoses. Unlike Babesia or Bartonella, which often produce chronic symptoms, Anaplasmosis typically presents as an acute febrile illness within 1-2 weeks of a tick bite—sometimes before Lyme disease symptoms even appear.
When Anaplasmosis is recognized early and treated appropriately, patients usually recover completely. But when it’s missed—dismissed as viral illness, attributed to other causes, or left untreated while waiting for test results—outcomes can be severe, including hospitalization, organ damage, or death in rare cases.
What Is Anaplasmosis?
Anaplasmosis is caused by Anaplasma phagocytophilum, a bacterium transmitted by Ixodes scapularis ticks—the same black-legged ticks that transmit Lyme disease, Babesia, and other coinfections. The bacteria invade white blood cells, particularly neutrophils, disrupting immune function and causing characteristic laboratory abnormalities.
Unlike Lyme disease, which can take days to weeks to produce symptoms, Anaplasmosis typically causes acute illness within 1-2 weeks of tick bite. The rapid onset and severity distinguish it from other tick-borne infections and demand prompt recognition and treatment.
Anaplasmosis Symptoms
Anaplasmosis presents as an acute febrile illness with symptoms appearing suddenly and progressing rapidly. The characteristic clinical picture includes high fever (often 102-104°F or higher), severe headache often described as the worst headache of the patient’s life, profound muscle aches and body pain, chills and rigors, nausea, vomiting, or diarrhea, and malaise and weakness out of proportion to other symptoms.
Unlike Lyme disease, Anaplasmosis rarely produces a rash. When rash does occur, it’s typically nonspecific and does not resemble erythema migrans. The absence of rash combined with severe systemic symptoms can lead to misdiagnosis as influenza or other viral illness.
Laboratory findings are characteristic and provide important diagnostic clues. Patients with Anaplasmosis typically show low white blood cell count (leukopenia), low platelet count (thrombocytopenia), and elevated liver enzymes. These abnormalities combined with acute fever in a patient with tick exposure should prompt consideration of Anaplasmosis even before confirmatory testing returns.
Why Anaplasmosis Is Missed
Anaplasmosis is frequently misdiagnosed as viral illness, particularly influenza. The acute onset, high fever, severe body aches, and absence of rash create a clinical picture that resembles flu more than typical Lyme disease. Patients presenting during flu season may be diagnosed presumptively as influenza without consideration of tick-borne illness.
The problem compounds when clinicians don’t ask about tick exposure or outdoor activities. A patient presenting with fever and body aches in July may have been hiking or gardening days earlier, but without specific questioning about ticks, the connection is missed.
Testing delays also contribute to missed diagnoses. Anaplasmosis serology may be negative early in infection, requiring convalescent titers weeks later to confirm diagnosis. PCR testing can identify infection earlier but isn’t universally available. By the time confirmatory results return, treatment may have been delayed for days or weeks.
Anaplasmosis and Lyme Disease Together
Because Anaplasmosis and Lyme disease are transmitted by the same tick, coinfection is common. A single tick bite can deliver both pathogens simultaneously, producing a clinical picture more severe than either infection alone.
Patients with both infections may experience the acute febrile illness of Anaplasmosis overlapping with the joint pain, neurologic symptoms, or fatigue characteristic of Lyme disease. The combination can be confusing diagnostically, particularly when symptoms don’t fit neat categories.
Fortunately, doxycycline—the first-line treatment for both Lyme disease and Anaplasmosis—addresses both infections simultaneously. When Anaplasmosis is suspected or confirmed in a Lyme patient, continuing doxycycline at appropriate doses treats both pathogens effectively.
Treatment and Recovery
Anaplasmosis responds rapidly to doxycycline. Most patients experience significant improvement within 24-48 hours of starting treatment, with fever resolving and symptoms beginning to abate. This dramatic response to doxycycline provides clinical confirmation of the diagnosis even when laboratory testing is pending.
Standard treatment is doxycycline 100mg twice daily for 10-14 days, though duration may be extended when Lyme disease coinfection is present or symptoms persist. Alternative antibiotics like rifampin can be used in patients who cannot take doxycycline, though doxycycline remains the preferred agent.
Delayed treatment increases the risk of severe complications including respiratory failure requiring mechanical ventilation, acute kidney injury, bleeding disorders from severe thrombocytopenia, neurologic complications including seizures or altered mental status, and secondary infections from immune suppression. These complications are preventable with prompt antibiotic therapy, making early recognition essential.
When to Suspect Anaplasmosis
Consider Anaplasmosis in any patient with acute febrile illness and tick exposure, particularly when laboratory findings show low white blood cells, low platelets, or elevated liver enzymes. The combination of severe headache, high fever, and characteristic lab abnormalities in a patient from an endemic area warrants empiric treatment with doxycycline while awaiting confirmatory testing.
The decision to treat empirically should not wait for test results. Anaplasmosis can progress rapidly, and delaying treatment while waiting for serology or PCR results can lead to preventable complications. When clinical suspicion is high, start doxycycline immediately—confirmatory testing can follow, but treatment should not be delayed.
Clinical Takeaways
Anaplasmosis is an acute bacterial coinfection transmitted by the same ticks that carry Lyme disease, affecting 5-10% of Lyme patients in endemic areas and presenting with high fever, severe headache, and characteristic laboratory abnormalities including low white blood cells and platelets. The infection is frequently misdiagnosed as influenza due to acute onset and systemic symptoms, particularly when clinicians don’t ask about tick exposure or consider tick-borne illness in the differential diagnosis. Fortunately, Anaplasmosis responds rapidly to doxycycline with most patients improving within 24-48 hours, though delayed treatment increases risk of severe complications including respiratory failure and organ damage. When acute febrile illness occurs with tick exposure and characteristic lab findings, empiric doxycycline treatment should begin immediately without waiting for confirmatory serology.
Frequently Asked Questions
What are the main symptoms of Anaplasmosis?
High fever (102-104°F), severe headache, profound muscle aches, chills, and systemic illness appearing suddenly within 1-2 weeks of tick bite. Lab findings show low white blood cells and platelets.
How is Anaplasmosis different from Lyme disease?
Anaplasmosis causes acute febrile illness within days, while Lyme disease typically develops over weeks. Anaplasmosis rarely produces rash and causes characteristic blood count abnormalities not seen in Lyme disease.
Can you have Anaplasmosis and Lyme disease at the same time?
Yes. Both are transmitted by the same tick, so coinfection is common. A single tick bite can deliver both pathogens simultaneously.
How is Anaplasmosis treated?
Doxycycline 100mg twice daily for 10-14 days. Most patients improve dramatically within 24-48 hours of starting treatment.
Is Anaplasmosis dangerous?
When treated promptly, most patients recover completely. Delayed treatment can lead to serious complications including respiratory failure, kidney injury, and neurologic problems.
References
- Bakken JS, Dumler JS. Human granulocytic anaplasmosis. Infect Dis Clin North Am. 2008;22(3):433-448.
- Dumler JS, et al. Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales. Int J Syst Evol Microbiol. 2001;51(6):2145-2165.
- Wormser GP, et al. A brief history of the clinical diagnosis and treatment of Lyme disease. Clin Infect Dis. 2006;43(9):1089-1098.
Related Reading
Anaplasmosis Information
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