Anaplasmosis case definition and report form

Human Anaplasmosis 2008 Public Health Surveillance Case Definition: 

This surveillance case definition was developed for national reporting of Human Anaplasmosis; it is not intended to be used in clinical diagnosis.

Clinical Description

Clinical presentation: A tick-borne illness characterized by acute onset of fever and one or more of the following symptoms or signs: headache, myalgia, malaise, anemia, leukopenia, thrombocytopenia, or elevated hepatic transaminases. Nausea, vomiting, or rash may be present in some cases.

Clinical evidence: Any reported fever and one or more of the following: headache, myalgia, anemia, leukopenia, thrombocytopenia, or any hepatic transaminase elevation.

 Anaplasma phagocytophilum infection (formerly Human Granulocytic Ehrlichiosis [HGE])

Laboratory criteria for diagnosis


  • Serological evidence of elevated IgG or IgM antibody reactive with A. phagocytophilum antigen by IFA, enzyme-linked immunosorbent Assay (ELISA), dot-ELISA, or assays in other formats (CDC uses an IFA IgG cutoff of ≥1:64 and does not use IgM test results independently as diagnostic support criteria.), OR
  • Identification of morulae in the cytoplasm of neutrophils or eosinophils by microscopic examination


  • Serological evidence of a fourfold change in IgG-specific antibody titer to A. phagocytophilum antigen by indirect immunofluorescence assay (IFA) in paired serum samples (one taken in first week of illness and a second 2-4 weeks later), OR
  • Detection of A. phagocytophilum DNA in a clinical specimen via amplification of a specific target by polymerase chain reaction (PCR) assay, OR
  • Demonstration of anaplasmal antigen in a biopsy/autopsy sample by immunohistochemical methods, OR
  • Isolation of A. phagocytophilum from a clinical specimen in cell culture


For confirmed and probable cases of anaplasmosis that have been identified and reported through the National Notifiable Disease Surveillance System, states are also encouraged to submit additional information using the CDC Case Report Form (CRF). This form collects additional important information that routine electronic reporting does not, such as information on how the diagnosis was made, and whether the patient was hospitalized or died. If a different state-specific form is already used to collect this information, this information may be submitted to CDC in lieu of a CRF.

2010 CDC Case Report Form: Tickborne Rickettsial Diseases (2010 version)  Adobe PDF file [PDF – 3 pages]