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ehrlichiosis

Etiology: - infection by Ehrlichia chaffeensis Epidemiology: 1) infection transmitted by tick Amblyomma americanum (Lone Star tick) 2) Ehrlichia chaffeensis is endemic in the same areas where Rickettsia rickettsii (etiologic agent of Rocky Mountain spotted fever) is found Clinical manifestations: 1) similiar to anaplasmosis 2) fever begins 1-2 weeks after tick bite [1] 3) headache 4) myalgias 5) maculopapular skin eruption (40%) a) spares extremities, palms, soles b) distinguishing feature from Rocky Mountain spotted fever is central distribution with peripheral sparing c) petechiae Laboratory: 1) abnormal serum transaminases [1] 2) complete blood count (CBC) a) leukopenia b) thrombocytopenia 3) Ehrlichia chaffeensis DNA - obtain specimen prior to initiation of antibiotic therapy 4) microscopic examination of peripheral blood [5] a) generally will NOT show organism b) staining of peripheral blood neutrophils & monocytes for morula or intracytoplasmic loose aggregrates of bacteria within monocytes (E. chaffeensis) or granulocytes (E. phagocytophilia & E. equi) is diagnostic 5) serology: acute & convalescent sera a) standard method b) may be negative early in disease (< 2-4 weeks) c) NOT useful for evaluating clearance of organism 6) see ARUP consult [3] Complications: - multiorgan failure - acute kidney injury, acute respiratory distress syndrome, meningoencephalitis [1] Differential diagnosis: - Rocky MOuntain spotted fever - rash involving distal extremities often involving palms & soles Management: - doxycycline PO or IV a) empiric treatment in patient with suspected disease b) delay in treatment associated with poor outcome; do not delay [1] c) response to treatment may occur in 1-3 days d) continue treatment for several days after patient has become afebrile - rifampin may be alternative in pregnant women [1]

Related

anaplasmosis Ehrlichia

Specific

Sennetsu fever

General

tick borne infection Rickettsia infection; Rickettsia spotted fever

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 16, 17, 18, 19. American College of Physicians, Philadelphia 1998, 2006, 2012, 2015, 2018, 2021. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  2. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 91
  3. ARUP Consult: Anaplasma phagocytophilum and Ehrlichia Species - Anaplasmosis and Ehrlichiosis The Physician's Guide to Laboratory Test Selection & Interpretation https://www.arupconsult.com/content/anaplasma-phagocytophilum-coltivirus-colorado-tick-fever-and-ehrlichia-species
  4. Ismail N, Bloch KC, McBride JW. Human ehrlichiosis and anaplasmosis. Clin Lab Med. 2010 Mar;30(1):261-92 PMID: 20513551
  5. Blevins SM, Greenfield RA, Bronze MS Blood smear analysis in babesiosis, ehrlichiosis, relapsing fever, malaria, and Chagas disease. Cleve Clin J Med. 2008 Jul;75(7):521-30 PMID: 18646588