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What Are Ehrlichia and Anaplasma?
Ehrlichia and Anaplasma are obligate intracellular bacteria transmitted by tick bites that cause two closely related diseases — ehrlichiosis and anaplasmosis (formerly known as human granulocytic ehrlichiosis). What makes these pathogens particularly insidious is their target: unlike most bacteria that reside in the bloodstream or tissues, Ehrlichia and Anaplasma invade and replicate within white blood cells — the very cells responsible for defending the body against infection.
By hijacking the immune system’s own soldiers, these bacteria create a state of immune suppression that complicates the body’s ability to fight concurrent infections. This is especially significant for patients co-infected with Borrelia burgdorferi (Lyme disease), as the immune impairment caused by Ehrlichia or Anaplasma can allow Borrelia to establish deeper, more treatment-resistant infection.
At St. George Hospital in Bad Aibling, Germany, Dr. Julian Douwes and our infectious disease team routinely screen for these co-infections as part of our comprehensive tick-borne disease evaluation. Failure to identify and treat Ehrlichia or Anaplasma is a recognized cause of incomplete recovery in Lyme disease patients.
Understanding the Biology
Ehrlichia Species
The primary species causing human disease are:
- Ehrlichia chaffeensis: The causative agent of human monocytic ehrlichiosis (HME), which infects monocytes and macrophages
- Ehrlichia ewingii: Causes a milder form of ehrlichiosis, infecting neutrophils
- Ehrlichia muris eauclairensis: A more recently identified species associated with disease in the upper Midwestern United States
Anaplasma phagocytophilum
Anaplasma phagocytophilum causes human granulocytic anaplasmosis (HGA), infecting neutrophils — the most abundant white blood cells and the immune system’s first responders against bacterial infection. By disabling these cells, Anaplasma effectively suppresses the innate immune response.
Both organisms form characteristic clusters called morulae within infected white blood cells — berry-like aggregates of bacteria enclosed in membrane-bound vacuoles. The identification of morulae on peripheral blood smear is diagnostic, though sensitivity is limited.
Shared Vector with Lyme Disease
Critically, Anaplasma phagocytophilum is transmitted by the same Ixodes tick species that carries Borrelia burgdorferi and Babesia. Ehrlichia chaffeensis is transmitted primarily by the Lone Star tick (Amblyomma americanum). The shared vector ecology means co-infection is common — a single tick bite can transmit multiple pathogens simultaneously.
A study in The Journal of Infectious Diseases found that approximately 10% of Lyme disease patients in endemic areas showed evidence of concurrent Anaplasma infection, highlighting the importance of comprehensive co-infection screening.
Symptoms of Ehrlichiosis and Anaplasmosis
The symptoms of ehrlichiosis and anaplasmosis overlap considerably with each other and with Lyme disease, making clinical differentiation challenging without laboratory testing.
Typical Symptom Presentation
- High fever: Often abrupt onset, with temperatures reaching 39–40°C (102–104°F)
- Severe headache: Frequently described as the worst headache of the patient’s life
- Profound malaise and fatigue: Debilitating weakness that can mimic influenza
- Myalgia: Diffuse muscle pain, often severe
- Nausea, vomiting, and abdominal pain: Gastrointestinal symptoms are common in ehrlichiosis
- Confusion and cognitive impairment: Neurological involvement may produce altered mental status
Distinctive Laboratory Findings
While symptoms may be nonspecific, certain laboratory abnormalities are highly suggestive of ehrlichiosis or anaplasmosis:
- Leukopenia: Low white blood cell count — a direct consequence of the bacteria destroying white blood cells
- Thrombocytopenia: Low platelet count, sometimes severely reduced
- Elevated liver enzymes: Transaminases (AST, ALT) are frequently elevated, indicating hepatic involvement
- Anemia: Mild to moderate, reflecting systemic inflammatory response
The combination of fever, headache, leukopenia, and thrombocytopenia following a tick bite should raise immediate suspicion for Ehrlichia or Anaplasma, even if Lyme disease is the primary clinical concern.
Severe and Complicated Disease
While most cases of ehrlichiosis and anaplasmosis are self-limited or respond well to treatment, severe complications can occur — particularly in immunocompromised, elderly, or untreated patients:
- Toxic shock-like syndrome
- Meningoencephalitis
- Acute respiratory distress syndrome (ARDS)
- Opportunistic infections due to immune suppression
- Disseminated intravascular coagulation (DIC)
The mortality rate for untreated ehrlichiosis is estimated at 1–3%, rising significantly in immunocompromised individuals. Anaplasmosis is generally less severe but can still produce serious complications, particularly in elderly patients.
Diagnostic Testing for Ehrlichia and Anaplasma
Accurate diagnosis of these co-infections requires awareness and appropriate testing — neither of which is guaranteed in standard clinical practice. Many physicians do not routinely test for Ehrlichia or Anaplasma, even in patients presenting with tick-borne illness.
Available Diagnostic Methods
Blood Smear Examination
Examination of a Wright- or Giemsa-stained peripheral blood smear for morulae within white blood cells is rapid and specific but has poor sensitivity — morulae are visible in only 20–80% of confirmed cases, depending on the timing of blood draw relative to infection.
PCR Testing
Polymerase chain reaction (PCR) testing for Ehrlichia and Anaplasma DNA is the most sensitive diagnostic method during acute infection. PCR can identify the specific species involved and is particularly valuable in the first 1–2 weeks of illness before antibodies develop.
Serological Testing
Indirect fluorescent antibody (IFA) testing measures antibody responses to Ehrlichia and Anaplasma. A fourfold rise in titer between acute and convalescent samples (drawn 2–4 weeks apart) is considered diagnostic. Single elevated titers may indicate past exposure rather than active infection.
Complete Blood Count (CBC)
While not diagnostic in itself, a CBC showing the characteristic triad of leukopenia, thrombocytopenia, and elevated liver enzymes provides important supportive evidence and should prompt specific testing.
Our Diagnostic Approach at St. George Hospital
Our comprehensive diagnostic laboratory employs a multi-method approach to co-infection testing. For patients presenting with suspected or confirmed Lyme disease, Dr. Julian Douwes routinely orders a complete co-infection panel that includes testing for Ehrlichia, Anaplasma, Babesia, Bartonella, and other relevant pathogens. This systematic approach ensures that no clinically significant co-infection is overlooked.
Treatment of Ehrlichiosis and Anaplasmosis
First-Line Antibiotic Therapy
Doxycycline is the treatment of choice for both ehrlichiosis and anaplasmosis in adults and children of all ages. Treatment should be initiated promptly upon clinical suspicion — waiting for laboratory confirmation can lead to disease progression. The standard regimen is:
- Doxycycline 100 mg twice daily for a minimum of 10–14 days, or at least 3 days after fever resolves, whichever is longer
For patients who cannot tolerate doxycycline, rifampin is an alternative for anaplasmosis, though its efficacy against Ehrlichia species is less well-established.
Treatment in the Context of Co-Infection
When Ehrlichia or Anaplasma co-infection accompanies Lyme disease, treatment protocols must address all pathogens. Fortunately, doxycycline has activity against Borrelia burgdorferi as well as Ehrlichia and Anaplasma, making it an efficient choice for co-infected patients. However, if Babesia is also present, additional antiparasitic therapy is required, as doxycycline has no activity against protozoan parasites.
Integrative Support at St. George Hospital
Beyond antimicrobial therapy, our treatment approach at St. George Hospital includes:
- Immune reconstitution: Since Ehrlichia and Anaplasma directly damage white blood cells, immune-supportive therapies are essential during recovery. This may include ozone therapy, micronutrient infusions, and targeted immunomodulation
- Hyperthermia therapy: Elevated body temperature supports immune function and creates an unfavorable environment for intracellular pathogens
- Detoxification support: Liver-supportive therapies to manage the metabolic burden of treating multiple concurrent infections
- Monitoring: Serial blood counts to track white blood cell and platelet recovery as markers of treatment response
The Relationship Between Ehrlichia, Anaplasma, and Chronic Lyme Disease
The clinical significance of Ehrlichia and Anaplasma extends beyond their acute symptoms. These infections may play an important role in the development of chronic, treatment-resistant Lyme disease through several mechanisms:
Immune Suppression Enables Borrelia Persistence
By destroying or disabling white blood cells, Ehrlichia and Anaplasma impair the immune system’s ability to control Borrelia. This may allow Lyme spirochetes to establish deeper tissue infection and form persister populations that are more resistant to antibiotic therapy.
Amplified Inflammatory Response
Co-infection triggers a more intense systemic inflammatory response than single infection, contributing to the severe fatigue, cognitive impairment, and pain that characterize chronic fatigue and post-treatment Lyme disease syndrome.
Diagnostic Confusion
Because Ehrlichia and Anaplasma symptoms overlap extensively with Lyme disease, co-infection may be attributed entirely to Lyme — leading to treatment protocols that address only one of the causative pathogens. A review in Ticks and Tick-borne Diseases emphasized the importance of comprehensive co-infection testing in all patients with suspected tick-borne illness.
Prevention
The same tick-avoidance measures that reduce Lyme disease risk apply to Ehrlichia and Anaplasma prevention:
- Use DEET or permethrin-based repellents in tick-endemic areas
- Wear long sleeves and pants when walking in wooded or grassy areas
- Perform thorough tick checks after outdoor activities
- Remove attached ticks promptly with fine-tipped tweezers
- Be aware that Lone Star ticks (Ehrlichia vector) are aggressive daytime biters, unlike the more passive Ixodes ticks
Frequently Asked Questions About Ehrlichia and Anaplasma
Can I have Ehrlichia or Anaplasma without knowing it?
Yes. Mild cases of anaplasmosis in particular may be dismissed as a “summer flu” and resolve without specific treatment in otherwise healthy individuals. However, even subclinical infection may compromise immune function, potentially facilitating the establishment or persistence of concurrent Lyme disease. If you have a history of tick exposure and are experiencing persistent symptoms, testing for these co-infections is advisable.
Are Ehrlichia and Anaplasma the same disease?
No, though they are closely related. Ehrlichia chaffeensis primarily infects monocytes (a type of white blood cell involved in adaptive immunity), while Anaplasma phagocytophilum infects neutrophils (the innate immune system’s first responders). The diseases they cause — ehrlichiosis and anaplasmosis — have overlapping symptoms but are caused by distinct organisms that may require slightly different diagnostic approaches.
How common is co-infection with Lyme disease?
Studies in endemic areas suggest that 2–15% of Lyme disease patients have concurrent Anaplasma infection, with rates varying by geographic region and tick population. Ehrlichia co-infection rates are less well-documented but are significant in areas where both Ixodes and Lone Star ticks are present. At St. George Hospital, we screen all Lyme disease patients for co-infections as standard practice.
Can Ehrlichia or Anaplasma become chronic?
Acute ehrlichiosis and anaplasmosis generally respond well to appropriate antibiotic therapy, and chronic carriage after adequate treatment is not well-documented. However, untreated or inadequately treated infection can persist, and the immune damage caused during acute infection may have lasting consequences — particularly in the context of multiple co-infections. Thorough treatment with post-treatment monitoring is essential.
Comprehensive Tick-Borne Disease Evaluation
If you have been diagnosed with Lyme disease but are not responding to treatment as expected, or if you have unexplained fevers, low blood counts, and severe fatigue following tick exposure, evaluation for Ehrlichia and Anaplasma co-infection may be critical to your recovery.
At St. George Hospital, our comprehensive approach to tick-borne illness ensures that all relevant pathogens are identified and treated. Contact our international patient team:
- Phone: +49 (0)8061 398-0
- Email: info@clinicum-stgeorg.de
- Online: Request a consultation
This article is for informational purposes only and does not constitute medical advice. Tick-borne diseases require qualified medical diagnosis and treatment. Individual results may vary.
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