Anaplasmosis

Case Definition

​​​​​​Confirmed Case

Laboratory confirmation of infection by one of the following methods with or without clinical evidence of illness1 (can include transfusion transmission):
  • Detection of Anaplasma phagocytophilum DNA in an appropriate clinical specimen by amplification of a specific target by Nucleic Acid Amplification Test (NAAT).
  • ​Serological evidence of a fourfold change in IgG-specific antibody titre to A. phagocytophilum antigen by indirect immunofluorescence assay (IFA) or enzyme immunoassay (EIA) if available in paired serum samples. The first sample taken in the acute phase (in first week of illness) and the second taken in the convalescent phase (2-4 weeks after the first sample).
  • Demonstration of A. phagocytophilum antigen in a biopsy/autopsy sample by immunohistochemical (IHC) methods.
  • Isolation of A. phagocytophilum from a clinical specimen in cell culture with confirmation by NAAT.

Probable case

Laboratory evidence of infection in the form of one of the following:
  • ​Serological evidence of elevated IgG antibody to A. phagocytophilum in a single specimen by IFA or EIA where the endpoint titre is fourfold greater than the screening dilution of the assay.
  • Identification of typical morulae in the cytoplasm of granulocytes by microscopic examination.
AND 

Clinical evidence of illness1 (can include transfusion transmission).

OR

A blood donor or recipient epidemiologically linked2 to a confirmed or probable anaplasmosis case.

1Clinical evidence of illness is characterized by fever and at least one of the following: headache, malaise/asthenia, arthralgia/myalgia, mild anemia, thrombocytopenia, leukopenia, elevated hepatic transaminase concentrations, or elevated numbers of immature neutrophils.  

2For the purposes of surveillance, epidemiologic linkage between a transfusion recipient and a blood donor is demonstrated if all of the following criteria are met:
  1. ​​Laboratory evidence of A. phagocytophilum infection in the recipient and donor.
  2. Transfusion recipient received one or more red blood cell (RBC) or platelet unit(s) within one year before the collection date of the recipient’s positive specimen.
  3. Transfused unit(s) was/were plausibly infectious based on assessment of donor infectivity at time of donation of implicated unit(s).
  4. Transfusion-associated infection in the recipient is considered at least as plausible as tick-borne transmission.