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Anaplasmosis and ehrlichiosis

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Rickettsial infections are caused by a variety of bacteria, and are most often transmitted to humans by  infected fleas, lice, mites, and ticks. Rickettsial infections include anaplasmosis, ehrlichiosis, Rocky Mountain spotted fever, and typhus fever group. 

AnaplasmosisPhoto of deer tick
(Anaplasma phagocytophilum infection)

Anaplasmosis, previously known as human granulocytic ehrlichiosis (HGE), is an illness caused by the bacterium Anaplasma phagocytophilum. Anaplasmosis is transmitted to humans through the bite of an infected deer or blacklegged tick (Ixodes scapularis), the same tick that causes other tickborne diseases in Wisconsin including Lyme disease. Illness occurs within 1-3 weeks after exposure to an infected tick. Symptoms may include fever, chills, muscle pain, severe headache, and fatigue. Clinical laboratory findings may include thrombocytopenia, lymphopenia, leucopenia, and elevated live enzymes. If not treated, anaplasmosis can lead to serious and occasionally fatal illness. Anaplasmosis is the second most reported tickborne disease in Wisconsin.

(Ehrlichia chaffeensis, Ehrlichia ewingii and Ehrlichia muris-like infection)

Ehrlichiosis is an illness caused by several species of Ehrlichia (E. chaffeensis, E. ewingii and Ehrlichia muris-like). In Wisconsin, ehrlichiosis is transmitted to humans through a bite of an infected deer or blacklegged tick (Ixodes scapularis), the same tick that causes other tickborne diseases. Since 2008, there has been an increase in reported cases of ehrlichiosis in Wisconsin. A new Ehrlichia species (Ehrlichia muris-like) was discovered in Wisconsin and Minnesota in 2009. Illness usually occurs between 5-10 days after exposure to an infected tick. Symptoms may include fever, chills, muscle pain severe headache, and fatigue. Less common signs and symptoms may include nausea, vomiting, diarrhea, joint pains, confusion, and rash. Clinical laboratory findings may include thrombocytopenia, lymphopenia, leucopenia, and elevated live enzymes. Ehrlichiosis can be more severe than anaplasmosis, and may involve the central nervous system, causing life-threatening complications. The number of reported ehrlichiosis cases is much lower than anaplasmosis in Wisconsin.

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General information
Anaplasmosis / Ehrlichiosis fact sheet  
Prevention and control of tickborne infections 
Anaplasmosis - CDC 
Ehrlichiosis - CDC  

Treatment information
Anaplasmosis treatment - CDC 
Ehrlichiosis treatment - CDC  

Data and statistics by disease
Historical ehrlichiosis surveillance included human granulocytic ehrlichiosis (HGE) and human monocytic ehrlichiosis (HME). As of 2008, the surveillance case definition changed to classify the disease by two different bacterial infections, Anaplasma phagocytophilum and Ehrlichia species.

    Total reported anaplasmosis and ehrlichiosis cases in Wisconsin from 1999 to 2010. Cases are separated by year of illness onset.

     Ehrlichia and anaplasma disease incidence for Wisconsin in 2010. Incidence is calculated as cases per 100,000 population. Counties depicted are based on county of residence.

Historical reports

Anaplasma phagocytophilum WI data and maps 2008-2012  
Anaplasma phagocytophilum
WI county counts 2008-2012

Ehrlichia chaffeensis WI data and maps 2008-2012
Ehrlichia chaffeensis WI county counts 2008-2012
Ehrlichia muris-like infection WI data and maps 2009-2012
Ehrlichia muris-like infection WI county counts 2009-2012  


    Combined case reporting prior to 2008
Anaplasmosis/Ehrlichiosis WI data 1999-2007 - Anaplasmosis map 2007

    Undetermined cases demonstrate cross reactivity or possible dual infection with more than one pathogen.
Anaplasmosis/Ehrlichiosis (undetermined) WI data and maps 2008-2012
Anaplasmosis/Ehrlichiosis (undetermined) WI county counts 2008-2012

Information for health professionals

  • This is a Wisconsin Disease Surveillance Category II disease: 
    Report to the patient's local public health department electronically, through the Wisconsin Electronic Disease Surveillance System (WEDSS), by mail or fax using an Acute and Communicable Disease Case Report F-44151 or by other means within 72 hours upon recognition of a case.
    Information on Communicable Disease Reporting

  • Wisconsin case reporting and public health follow-up guidelines: Anaplasmosis / Ehrlichiosis EpiNet

  • Tickborne Rickettsial disease case report form 

  • Laboratory
    • Because Anaplasma and Ehrlichia infections can have similar signs and symptoms, diagnostic tests are important to identify the specific agent causing illness. All patients who warrant testing for Anaplasma should also be tested for Ehrlichia. In WI, a panel testing for Anaplasma and Ehrlichia should be performed. PCR is the preferred diagnostic test because it is highly sensitive and specific during the acute disease phase. PCR testing should be performed using EDTA whole blood collected upon the initial physician's visit, prior to initiation of antibiotics. Because testing for E. muris-like species is only currently available commercial by PCR and not available by serology, it is important for providers who routinely perform serologic testing to collect an additional sample for PCR testing of E. muris-like species if this agent is suspected.

    • Serologic testing is the most common test performed in WI 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 E. chaffeensis infection requires evidence of a four-fold change 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 collected 2-4 weeks later. IgM antibody test results are not as reliable as IgG test results because IgM is less specific and can persist for a long period of time (3). Because cross-reactivity between A. phagocytophilum and E. chaffeensis frequently occurs with serologic testing, the agent demonstrating a higher titer (at least 4-fold) is the most likely agent causing illness. If a laboratory routinely performs only peripheral blood smears, the MDH and WDPH recommend that blood smear testing should be accompanied by a PCR or an IFA test for more definitive results.

    • Anaplasma Laboratory Tests - CDC  

    • Ehrlichia Laboratory Tests - CDC 

  • Treatment

    • Treatment for anaplasmosis and ehrlichiosis should not be delayed while awaiting further laboratory test results, but should be started based on compatible clinical signs and symptoms, initial supportive laboratory tests, and an assessment of the patient's likelihood of tick exposure.

  • Training

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Wisconsin Local Health Departments - Regional offices - Tribal agencies

Diep Hoang Johnson Vectorborne Disease Epidemiologist
Wisconsin Division of Public Health 
Bureau of Communicable Diseases and Emergency Response
(Phone 608-267-0249)  (Fax 608-261-4976)

Last Revised: March 25, 2014