Ehrlichiosis

1
Ehrlichiosis

• Catherine Hathaway
• Morning Report
• 10/6/08

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The bug

• Ehrlichia chaffeensis accounts for most cases of
  ehrlichiosis. (HME)
• Ehrlichia ewingii
• Anaplasma phagocytophilum (HGA)
• Obligate intracellular pathogen
• Transmitted by ticks
• Gram negative coccobacillary bacteria that
  targets granulocytes
• 5-7 days after infection can see morulae within
  granulocytes

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Morulae within granulocyte
The morulae form within the white cells then will
often burst releasing the ehrlichia into the
blood stream and then will infect other
cells. Morulae are more common with HGA than
HME, but can occur in both
4
Tick borne illness

• All have a similar presentation. Fever, headache,
  malaise.
• One series top 3 symptoms fever, rigors, HA
• Summer time
• Location
• Labs similar, thrombocytopenia, transaminitis,
  anemia, hyponatremia
• 70 of cases of ehrlichia occur in 7 states NC,
  MO, AR, GA, MD, OK, TN

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Ehrlichiosis

• Incidence 0.6/million in 2001-2002, but has since
  doubled to 1.2/million, case fatality rate of 3
• Fever, myalgia, headache most common. Nausea and
  vomiting can occur.
• Rash unlikely, but in severe cases can get DIC
  and associated petechiae
• Lymphadenopathy not common
• Can have hepatomegaly
• Labs can have elevated Cr, low Na,
  transaminitis, leukopenia and neutropenia

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Ehrlichia vs RMSF

• Ehrlichia very rarely has rash, in fact suspected
  that many cases of rashless RMSF were probably
  Ehrlichia
• Morulae seen on smear are diagnostic of ehrlichia
• Neutropenia more likely in Ehrlichia
• Anemia uncommoni n Ehrlichia

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HME vs HGA

• More likely to have rash if present.
• Meningitis/meningoencephalitis common
• Respiratory distress more common
• GI upset more likely
• Higher mortality (3 vs 0.7)

• More likely to have morulae seen on smear
• Less likely to present with shock/DIC
• Peripheral neuropathy can be present

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Other things on the Differential

• RMSF
• Babesiosis
• Chagas disease
• Malaria
• Relapsing fever

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When thinking tick.

• Think DOXYCYCLINE!! Just give it.
• Hamburg et al did study that showed delayed
  treatment with doxycycline resulted in longer
  hospital stay, more likely need for ICU care,
  worse laboratory values hg/lfts, and pulmonary
  involvement
• Ehrlichiosis can be fatal!

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Vector

• Amblyomma americanum (Lone Star tick) is the
  principle tick vector of HME.
• HGE can be transmitted by Ixodes persulcatus
  ticks andDermacentor variabilis (dog tick/wood
  tick).
• Found in Northeast, California, Texas, Southeast

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Creepy crawlies
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Diagnosis

• Early in the disease patient may not have
  positive serology, can use PCR
• If gt4 fold IgG as well as presence of IgM then
  suggests current or recent disease
• Do not delay treatment waiting for serology or
  lab confirmation
• Usually 1 week after tick bite, but often
  patients dont recall a bite

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Prognosis

• If suspected and treated early the prognosis is
  very good.
• As per above, delay in treatment can lead to more
  morbidity and even mortality
• Chloramphenicol is not useful in Ehrlichia. Some
  success with FQ as well as rifampin. However
  clearly doxycycline is preferred.
• Doxycycline should be given for 7-14 days

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Resources

• Hamburg, Brian J. MD Storch, Gregory A. MD
  Micek, Scott T. PharmD, BCPS Kollef, Marin H.
  MD. The importance of early treatment with
  doxycycline in human ehrlichiosis. IssueVolume
  87(2), March 2008, pp 53-60
• Cunha, Burke. Ehrlichiosis. Emedicine. Last
  updated August 25, 2006. Date accessed 10/5/08.
• Prince, Lisa. Ehrlichiosis, making the diagnosis
  in the acute setting. SMJ 2007 100(8).
• Openshaw, John. Human Ehrlichiosis Clinical and
  Ecological Challenges. SMJ 2007 100(8).
• Dumler, Stephen. Ehlichiosis in Humans, Clinical
  Presentation, Diagnosis, and Treatment. Clincial
  Infectious Diseases. 200745S45-S51.