CLINICAL DESCRIPTION
A tick borne febrile illness most commonly characterized by acute onset, accompanied by headache, myalgia, rigors and/or malaise. The incubation period is 7 to 21 days. The disease course is usually benign. Clinical laboratory findings may include intracyto-..plasmic microcolonies (morulae) in leukocytes of a peripheral smear, cerebrospinal fluid, or bone marrow aspirate or biopsy, cytopenias (especially thrombocytopenia and leukopenia), and elevated liver enzymes.

There are two clinically similar yet serologically distinct forms of ehrlichiosis: a) human granulocytic ehrlichiosis (HGE), caused by infection with an Ehrlichia equi - like agent and found primarily in the upper midwest and northeast, and b) human monocytic ehrlichiosis (HME) caused by Ehrlichia chaffeensis infection and found primarily in the southeastern quadrant of the United States.

CASE CLASSIFICATION

1. CONFIRMED
Clinical diagnosis confirmed by:
• Fourfold or greater increase in antibody titer to Ehrlichia spp. antigen by immunofluorescence antibody test (IFA), in acute and convalescent-phase specimens ideally taken greater or equal to 4 weeks apart. HME diagnosis requires E. chaffeensis antigen, and HGE currently requires E.equi or HGE-agent antigen, OR
• Positive polymerase chain reaction (PCR) assay for either organism, OR
• Intracytoplasmic morulae identified in blood, bone marrow, or CSF leukocytes, AND an IFA antibody titer greater than or equal to 64.
  
  
2. PROBABLE
   
   
   • A clinically compatible case with either a single IFA titer equal or greater than 64 OR
     
   • Intracytoplasmic morulae identified in blood, bone marrow, or CSF leukocytes.
     
     
3. POSSIBLE

Not used.

What you should know about Ehrlichiosis?