Anaplasmosis: Reporting and Surveillance

Anaplasmosis is a category II reportable condition in Wisconsin. Health care providers should report to the patient's local public health department:

Reporting should be completed within 72 hours upon recognition of a case or a suspected case. For more information, please visit the DHS Disease Reporting page.

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 Guidance Resources

DHS surveillance resources
Provider resources

 Testing

Anaplasma and Ehrlichia infections can have similar signs and symptoms, so the use of diagnostic tests are important to identify the specific agent causing illness. All patients who warrant testing for Anaplasma should also be tested for Ehrlichia.

Select the tabs below to learn about different laboratory tests for anaplasmosis.

PCR

PCR is the preferred diagnostic test because it is highly sensitive and specific during the acute disease phase. PCR testing should be performed using whole blood collected upon the initial physician's visit, before starting antibiotics. A positive PCR result is confirmation of A. phagocytophilum infection. It is important to note that a negative result does not rule out infection, and treatment should not be withheld due to a negative result.

Serologic Testing (IFA/EIA)

Serologic testing is the most common test performed in Wisconsin, even though it is less specific than the PCR test, and cross-reactivity often occurs among the Anaplasma and Ehrlichia agents. Serologic confirmation of A. phagocytophilum or Ehrlichia species infection requires evidence of a four-fold change (e.g. 1:64 to 1:256, or 1:128 to 1:512, etc.) in immunoglobulin G (IgG) specific antibody titer between paired acute and convalescent sera tested by indirect immunofluorescence assay (IFA).

  • The acute sample should be collected during the first week of illness, and the convalescent sample should be collected two to four weeks later.
  • Positive IgG titers can indicate a current or past infection.
  • IgM antibody test results are not as reliable as IgG test results, because they are less specific. Single IgM antibody tests should not be used for diagnosis.
  • Serologic tests based on enzyme immunoassay (EIA) only provide a positive or negative result, and cannot be used to measure changes in antibody titers between paired sera.

Cross-reactivity between A. phagocytophilum and Ehrlichia species frequently occurs with serologic testing. Therefore, the agent demonstrating a higher titer (at least four-fold higher) is the most likely agent causing illness. If there is less than a four-fold difference in titer, the agent will be undetermined.

Smear/Morulae

Early in illness, a blood smear might reveal morulae in the cytoplasm of granulocytes. This evidence can support an anaplasmosis diagnosis, but should not be relied upon solely as it is relatively insensitive. If a laboratory routinely performs only peripheral blood smears, the Division of Public Health recommends that blood smear testing should be accompanied by a PCR or an IFA test for more definitive results.

IHC Detection/Cell Culture

These are less commonly reported positive laboratory results, but are considered confirmatory. It is very rare to see these types of test results.

 Clinically Compatible Illness

In addition to having a positive lab result, a patient must also have clinically compatible illness. In order for an illness to be clinically compatible, the patient must exhibit:

Fever, sweats, or chills AND at least one of the following:

  • Headache
  • Myalgia (body aches)
  • Anemia (low red blood cell count)
  • Leukopenia (low white blood cell count)
  • Thrombocytopenia (low platelet count)
  • Elevated liver enzymes
  • Eschar (dark scab around the site of tick bite)
  • Rash (rare with anaplasmosis)

 Treatment

Treatment for anaplasmosis should not be delayed while awaiting laboratory test results, or be withheld on the basis of an initial negative laboratory result, but should be started based on clinically compatible signs and symptoms and an assessment of the patient's likelihood of tick exposure. Treatment should be started immediately whenever anaplasmosis is suspected.


Anaplasmosis can be treated with antibiotics. Doxycycline is the antibiotic of choice for adults and children of all ages. Most people treated with oral antibiotics during the early stages of anaplasmosis recover completely. Some patients may continue to have a headache, weakness, and malaise for weeks after adequate treatment.

The following table shows the current treatment recommendations from CDC for anaplasmosis in adults and children.

Treatment for Anaplasmosis
Age Category Drug Dosage Maximum Duration, Days
Adults Doxycycline 100 mg, twice per day 100 mg/dose 7–14
Children under 45 kg (100 lbs) Doxycycline 2.2 mg/kg body weight, twice per day 100 mg/dose 7–14

Antibiotic treatment following a tick bite is not recommended to prevent anaplasmosis. There is no evidence this practice is effective, and this may only delay onset of disease.

Questions about illnesses spread by ticks? Contact us!
Phone: 608-267-9003 | Fax: 608-261-4976

Last Revised: October 26, 2021