Dive into the complexities of anaplasmosis, a tickborne illness caused by Anaplasma phagocytophilum.
Explore its symptoms, diagnostic methods, and treatment options. Learn how to recognize early signs, navigate laboratory findings, and understand the importance of prompt medical attention in combating this emerging health concern.
This article explores is part one of a four part CME series “Diagnosis and Treatment of Four Tickborne Diseases: Lyme Disease, Ehrlichiosis, Anaplasmosis and Babesiosis” .
ANAPLASMOSIS (Part 3)
Anaplasmosis, also known as human granulocytic anaplasmosis, is a tickborne disease caused by the bacterium Anaplasma phagocytophilum.
Blacklegged ticks, Ixodes scapularis, in the eastern United States, and western blacklegged ticks, Ixodes pacificus, on the West Coast are the main causes of infection. Coinfections with other tickborne illness such as Lyme disease have been reported. Infections have occasionally been reported through blood transfusion and organ donation.[32]
Peak transmission is during June to November. Two peaks of increased case reporting usually occur, with the first peak during June–July and a smaller peak during October-November. There are about 4,000 to 5,700 cases reported per year to the CDC.[33]
Signs and Symptoms of Early Illness of Anaplasmosis [34]
Signs and symptoms typically begin within 5-14 days after the bite of an infected tick, and are non-specific. They may include:
Fever, chills, rigors
Severe headache
Malaise
Myalgia
Gastrointestinal symptoms (nausea, vomiting, diarrhea, anorexia) in about 20% of cases
A non-specific rash occurs in less than 10% of patients with anaplasmosis. As rash is a rare finding in anaplasmosis, if a rash is present, consider a coinfection with Lyme disease, or another tickborne disease.
Rarely: Nervous system involvement (e.g., meningoencephalitis, focal paralysis)
Late Illness Symptoms of Anaplasmosis [34]
If treatment is delayed severe illness can occur but is rare. Symptoms may include:
Renal or respiratory failure
Peripheral neuropathies
Disseminated intravascular coagulation (DIC)-like coagulopathies
Rhabdomyolysis
Hemorrhage
The clinical course of anaplasmosis varies from person to person, and may depend on patient age, co-morbid conditions, immune status and time of treatment.
Laboratory Findings in Anaplasmosis [34]
Laboratory findings can include mild anemia, thrombocytopenia, leukopenia and mild to moderate elevations in hepatic transaminases. However, normal laboratory findings do not rule out possible infection.
Testing for Anaplasmosis [35]
Laboratory testing for anaplasmosis is similar to ehrlichiosis.
Indirect immunofluorescence antibody (IFA) assay for IgG using Anaplasma phagocytophilum antigen, is the standard diagnostic test for anaplasmosis. IgG IFA assays should be performed on paired acute and convalescent serum samples collected 2–4 weeks apart to demonstrate evidence of a fourfold rise. Antibody titers are frequently negative in the first week of illness. Anaplasmosis cannot be confirmed using a single acute antibody test. Between 5–10% of healthy people in some areas might have elevated antibody titers due to past exposure to A. phagocytophilum or similar organisms, which is why comparison of paired, serologic assays provides the best evidence of recent infection. Some reference laboratories offer IgM IFA assays which are not necessarily indicators of acute infection, and might be less specific than IgG antibodies. Therefore, IgM antibody titers alone should not be used for laboratory diagnosis.
Polymerase chain reaction (PCR) amplification can be performed on DNA extracted from whole blood specimens. PCR is most sensitive in the first week of illness, and decreases in sensitivity following the administration of appropriate antibiotics. Unfortunately, a negative result does not rule out the diagnosis. PCR can also be used to amplify DNA in solid tissue and bone marrow specimens for testing.
During the first week of illness a peripheral blood smear might reveal morulae (microcolonies of anaplasmae) in the cytoplasm of granulocytes and is highly suggestive of a diagnosis. However, blood smear examination is relatively insensitive, and should not be relied upon solely to diagnose anaplasmosis. The observance of morulae in a particular cell type cannot reliably differentiate between Anaplasma and Ehrlichia species. If a bone marrow biopsy is performed as part of the investigation of cytopenias, immunostaining of the bone marrow biopsy specimen looking for morulae can diagnose anaplasmosis. They may also be seen in organ biopsies taken for other purposes.
Culture of A. phagocytophilum is only available at specialized laboratories, and routine hospital blood cultures cannot detect the organism
Treatment of Anaplasmosis [36]
Post-tick bite antibiotic prophylaxis is not currently recommended to prevent anaplasmosis.
Doxycycline is recommended as the first-line treatment for anaplasmosis in adults and children of all ages. The dosage in adults is 100 mg every 12 hours, in children under 45 kg (100 lbs.)the dose is 2.2 mg/kg body weight given twice a day.
Patients with suspected anaplasmosis should be treated with doxycycline for 10–14 days to provide appropriate length of therapy for possible concurrent Lyme disease infection. Lack of a clinical response to doxycycline suggests that the patient’s condition might not be due to anaplasmosis, or might be a due to a coinfection. Resistance to doxycycline or relapses in anaplasmosis symptoms after the completion of the recommended course have not been documented.
In cases of life-threatening allergies to doxycycline, severe doxycycline intolerance, and in some pregnant patients for whom the clinical course of anaplasmosis appears mild, rifampin might be considered. Rifampin has been used successfully in several pregnant women with anaplasmosis, and small numbers of children <8 years for a 7–10-day course. However, rifampin is not effective in treating Rocky mountain spotted fever, a disease that might be confused with anaplasmosis, nor is it an effective treatment for a potential Lyme disease coinfection. An infectious disease consult is recommended when treating the pregnant patient.
More TICK-BORNE Disease articles: Lyme | Ehrlichiosis | Babesia
The CME version of this article is available for the medical community with an online CME test in the APP.
REFERENCES
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