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Ehrlichiosis (HGE, HME, other or unspecified)
2000 Case Definition
Clinical description
A tick-borne illness characterized by acute onset of fever,
headache, myalgia, and/or malaise. Nausea, vomiting, or rash may be present
in some cases. Clinical laboratory findings may include thrombocytopenia,
leukopenia, and/or elevated liver enzymes. Intracytoplasmic bacterial
aggregates (morulae) may be visible in the leukocytes of some patients.
Three categories of confirmed or probable ehrlichiosis
should be reported: 1) human ehrlichiosis caused by E. chaffeensis
(HME), 2) human ehrlichiosis caused by E. phagocytophila (HGE), and
3) human ehrlichiosis (other or unspecified agent), which includes
cases that cannot be easily classified by available laboratory techniques,
and cases caused by novel Ehrlichia species such as E. ewingii.
Laboratory criteria for diagnosis
HME:
- Demonstration of a four-fold change in antibody
titer to E. chaffeensis antigen by indirect immunofluorescence
assay (IFA) in paired serum samples, or
- Positive polymerase chain reaction (PCR) assay and
confirmation of E. chaffeensis DNA, or
- Identification of morulae in leukocytes, and a positive
IFA titer to E. chaffeensis antigen (based on cutoff titers established
by the laboratory performing the assay), or
- Immunostaining of E. chaffeensis antigen in a biopsy
or autopsy sample, or
- Culture of E. chaffeensis from a clinical specimen.
HGE:
- Demonstration of a four-fold change in antibody
titer to E. phagocytophila antigen by IFA in paired serum samples,
or
- Positive PCR assay and confirmation of E. phagocytophila
DNA, or
- Identification of morulae in leukocytes, and a positive
IFA titer to E. phagocytophila antigen (based on cutoff titers
established by the laboratory performing the assay), or
- Immunostaining of E. phagocytophila antigen in a
biopsy or autopsy sample, or
- Culture of E. phagocytophila from a clinical specimen.
Ehrlichiosis ,human, other or unspecified agent:
- Demonstration of a four-fold change in antibody
titer to more than one Ehrlichia species by IFA in paired serum
samples, in which a dominant reactivity cannot be established,
or
- Identification of an Ehrlichia species other than
E. chaffeensis or E. phagocytophila by PCR, immunostaining, or
culture.
Case classification
Probable: a clinically
compatible illness with either a single positive IFA titer (based
on cutoff titers established by the laboratory performing the test)
or the visualization of morulae in leukocytes.
Confirmed: a clinically compatible illness
that is laboratory-confirmed.
See also:
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