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The Ehrlichioses

The Ehrlichioses. William Kwan UNC Medicine-Pediatrics. Objectives. Overview of 3 human Ehrlichioses Microbiology Epidemiology Diagnosis Treatment. Microbiology of Ehrlichiae. Gram-negative obligate intracellular bacteria that grow in vacuoles (morulae)

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The Ehrlichioses

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  1. The Ehrlichioses William Kwan UNC Medicine-Pediatrics

  2. Objectives • Overview of 3 human Ehrlichioses • Microbiology • Epidemiology • Diagnosis • Treatment

  3. Microbiology of Ehrlichiae • Gram-negative obligate intracellular bacteria that grow in vacuoles (morulae) • Two Ehrlichiae species and Anaplasma cause three forms of human Ehrlichioses • Ehrlichia chaffeensis • Ehrlichia ewingii • Anaplasma phagocytophila

  4. Human Monocytic Ehrlichiosis (HME) • Agent: Ehrlichia chaffeensis • Vector: Lone Star tick (and sometimes Dog tick) • Higher prevalence during late spring and early summer • Southeast, south central, and mid-Atlantic • Fever (97%), malaise (84%), headache (81%), myalgia (68%) • Diarrhea (25-68%), rash (36%, but only 6% at presentation), confusion (20%) • Complications: ARDS, meningoencephalitis, fulminant infection, hemorrhage • Mortality in 2-5% • Leukopenia (60-74%), thrombocytopenia (72%), elevated LFT’s (90%)

  5. Human Monocytic Ehrlichiosis (HME) • Diagnosis based on clinical suspicion • Most common diagnostic test: Serology using indirect fluorescence antibody to E. chaffeensis • Fourfold rise in titers between acute sera (on presentation) and convalescent sera (drawn 2-4 weeks later) • Single titer of 1:128 may be diagnostic but no established threshold

  6. Human Monocytic Ehrlichiosis (HME) • Peripheral blood smear or examination of buffy coat may show rare morulae (1-20%)

  7. Human Monocytic Ehrlichiosis (HME) • Peripheral blood smear or examination of buff coat may show rare morulae (1-20%) • PCR techniques being developed • Immunochemical staining of tissue (e.g. lymph nodes, liver, spleen, lung)

  8. Human Monocytic Ehrlichiosis (HME) • Treatment of choice: Doxycycline 100mg bid x 10 days or up to 3-5 days following defervescence • Alternative choice: Rifampin 300mg x 7-10 days • Pregnancy: • If disease not life-threatening: Rifampin • If disease life-threatening: Doxycycline

  9. Human Granulocytic Anaplasmosis (HGA) • Formerly called Human Granylocytic Ehrlichiosis • Agent: Anaplasma phagocytophila • Vector: Deer tick • Higher prevalence during late spring and early summer • Northeast • Symptoms are very similar to those in HME • Exception: Rash is very rare • Leukopenia, thrombocytopenia, elevated LFT’s • May have concurrent infection with Lyme Disease and much less commonly Babesiosis

  10. Human Granulocytic Anaplasmosis (HGA) • Initial diagnosis based on clinical suspicion • Serology using IFA to A. phagocytophila • Four-fold rise in titers between acute and convalescent sera • Peripheral blood smear or buffy coat examination may show morulae (20-80%, higher than for HME) • PCR • Immunochemical tissue staining • Treatment is same as for HME: Doxycycline (or Rifampin)

  11. Ehrlichiosis Ewingii • Agent: E. ewingii • Vector: Lone Star tick • Higher prevalence during summer • Symptoms similar to HME but less severe • Usually diagnosed in immunocompromised • IFA utilizes E. chaffeensis antigen • No criteria for diagnostic serologies • Treat with Doxycycline

  12. Take-Home Points • HME and HGA are very similar diseases • HME more common in southeast, south central, mid-Atlantic • HGA more common in northeast • HGA may be accompanied by Lyme Disease • Treatment is Doxycycline 100mg bid x 7-10 days or up to 3-5 days after defervescence • Rifampin may be used in pregnant patients with non-life threatening disease • Bacteria cartoons are corny

  13. References • Dumler et al., “Ehrlichioses in Humans: Epidemiology, Clinical Presentation, Diagnosis, and Treatment.” The Journal of Clinical Infectious Diseases. July 2007; 45: S45-51. • Kasper et al., Harrison’s Principles of Internal Medicine. 16th ed. New York: McGraw Hill, 2005. • Sexton et al., “The Human Ehrlichioses.” UpToDate Online. • Stone et al., “Human Monocytic Ehrlichiosis.” Journal of the American Medical Association. November 10, 2004; 292: 2263 - 227.

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