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anaplasmosis

Etiology: - Anaplasma phagocytophilum Epidemiology: - reservoir: deer & rodents - vectors: ticks: Ixodes scapularis, Dermacentor variabilis - same vectors as Lyme disease - most commonly encountered April-September - infrequently found in Caribbean [1] Pathology: - tickborne rickettsial infection of neutrophils Clinical manifestations: - may be evidence suggesting tick bite - may present as coinfection with Lyme disease [1,4] - symptoms similar to ehrlichiosis - fever 1-2 weeks after tick bite - headache - myalgia - arthralgia - rash less common than ehrlichiosis (uncommon) [1] - symptoms may persist for months in untreated patients - chronic fatigue is NOT characteristic * same tick vectors as Lyme disease Laboratory: - complete blood count (CBC) - leukopenia (variable), thrombocytopenia - chemistry 14 panel - elevated serum transaminases (~ 2-fold) [1] - case report of hyponatremia (serum sodium = 130 mmol/L) [5] - Anaplasma phagocytophilum DNA - Anaplasma marginale DNA or Anaplasma marginale rRNA - microscopic examination of peripheral blood smear 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 (A phagocytophilum) is diagnostic - serology: acute & convalescent serum - may be negative early in the disease (< 2-4 weeks) Differential diagnosis: - ehrlichiosis: a) Ehrlichia chaffensis infects monocytes b) truncal skin rash in 40% Complications: - multiorgan failure; mortality 3% in treated patients - acute kidney injury, acute respiratory distress syndrome, meningoencephalitis [1] - coinfection with another tick-borne infection may occur [1] Management: - doxycycline PO or IV for 10-14 days [5] a) empiric treatment in patient with suspected disease b) delayed treatment associated with poor outcome [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

Anaplasma phagocytophilum (Ehrlichia equi) ehrlichiosis

General

tick borne infection Rickettsia infection; Rickettsia spotted fever

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 17, 18, 19. American College of Physicians, Philadelphia 2009, 2012, 2015, 2018, 2021. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  2. Dumler JS, Choi K, Garcia-Garcia JC, Barat NS, Scorpio DG, Garyu JW, et al. Human granulocytic anaplasmosis and Anaplasma phagocytophilum. Emerg Infect Dis [serial on the Internet]. 2005 Dec http://www.cdc.gov/ncidod/EID/vol11no12/05-0898.htm
  3. Ismail N, Bloch KC, McBride JW. Human ehrlichiosis and anaplasmosis. Clin Lab Med. 2010 Mar;30(1):261-92 PMID: 20513551
  4. Horowitz HW, Aguero-Rosenfeld ME, Holmgren D et al Lyme disease and human granulocytic anaplasmosis coinfection: impact of case definition on coinfection rates and illness severity. Clin Infect Dis. 2013 Jan;56(1):93-9. PMID: 23042964 Free Article
  5. Kobayashi KJ, Weil AA, Branda JA Case 16-2018: A 45-Year-Old Man with Fever, Thrombocytopenia, and Elevated Aminotransferase Levels. N Engl J Med 2018; 378:2023-2029. May 24, 2018 https://www.nejm.org/doi/full/10.1056/NEJMcpc1712227
  6. 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