Ehrlichiosis Differential Diagnoses

Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD more...

Updated: Nov 3, 2011

What would you like to print?

Diagnostic Considerations

Ehrlichiosis is a difficult infectious disease to diagnose because it manifests as an acute, undifferentiated, febrile, RMSF-like illness with few or no physical findings. Most patients who are diagnosed with RMSF without rash probably have ehrlichiosis. Co-infections of various tick-borne pathogens transmitted by the same vector are rare, but they do occur.

Ehrlichiosis has the same distribution as RMSF and is transmitted by the same tick species (eg, Amblyomma, Dermacentor). However, RMSF causes physical findings that ehrlichiosis does not, including bilateral periorbital edema, edema of the dorsum of the hands and feet, and conjunctival suffusion. The petechial rash of RMSF is absent in ehrlichiosis.

Laboratory findings associated with RMSF and ehrlichiosis are similar (eg, thrombocytopenia, relative lymphopenia, increased levels of serum transaminases, atypical lymphocytes). However, neutropenia is more common in ehrlichiosis than in RMSF.

Most patients with ehrlichiosis present with fever and a severe headache but do not have nuchal rigidity, as opposed to patients with aseptic or bacterial meningitis. The cerebrospinal fluid (CSF) profile in patients with ehrlichiosis is normal, in contrast to patients with viral or bacterial meningitis.

Other differential diagnostic possibilities include typhoid fever, malaria, and babesiosis. All of these infectious diseases manifest as acute, undifferentiated, febrile illnesses with a paucity of physical signs. The diagnosis of typhoid fever and malaria are suggested by an appropriate epidemiologic profile and/or travel history. Exposure to large Dermacentor ticks would suggest RMSF, whereas exposure to small Ixodes ticks would suggest the possibility of babesiosis.

Differential Diagnoses

Proceed to Workup

Contributor Information and Disclosures

Author

Burke A Cunha, MD Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Coauthor(s)

Samuel M Keim, MD Associate Professor, Department of Emergency Medicine, University of Arizona College of Medicine

Samuel M Keim, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Public Health Association, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Walid Abuhammour, MD, FAAP Professor of Pediatrics, Michigan State University College of Medicine; Director of Pediatric Infectious Disease, Department of Pediatrics, Hurley Medical Center

Walid Abuhammour, MD, FAAP is a member of the following medical societies: American Medical Association, Infectious Diseases Society of America, and Pediatric Infectious Diseases Society

Disclosure: Nothing to disclose.

Joseph Domachowske, MD Professor of Pediatrics, Microbiology and Immunology, Department of Pediatrics, Division of Infectious Diseases, State University of New York Upstate Medical University

Joseph Domachowske, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Society for Microbiology, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Geofrey Nochimson, MD Consulting Staff, Department of Emergency Medicine, Sentara Careplex Hospital

Geofrey Nochimson, MD is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

Nicholas John Bennett, MB, BCh, PhD Fellow in Pediatric Infectious Disease, Department of Pediatrics, State University of New York Upstate Medical University

Nicholas John Bennett, MB, BCh, PhD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Pediatrics

Disclosure: Nothing to disclose.

Specialty Editor Board

Thomas J Marrie, MD Dean of Faculty of Medicine, Dalhousie University Faculty of Medicine, Canada

Thomas J Marrie, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society for Microbiology, Canadian Infectious Disease Society, and Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Jon Mark Hirshon, MD, MPH Associate Professor, Department of Emergency Medicine, University of Maryland School of Medicine

Jon Mark Hirshon, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Public Health Association, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Russell W Steele, MD Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine

Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association

Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD Professor, Stewart G Wolf Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Medical Association, Association of Professors of Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, and Southern Society for Clinical Investigation

Disclosure: Nothing to disclose.

References

CDC. Ehrlichiosis. Accessed May 16 2011. Available at http://www.cdc.gov/ehrlichiosis.
Chapman AS, Bakken JS, Folk SM, et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis--United States: a practical guide for physicians and other health-care and public health professionals. MMWR Recomm Rep. Mar 31 2006;55:1-27. [Medline].
Buller RS, Arens M, Hmiel SP, et al. Ehrlichia ewingii, a newly recognized agent of human ehrlichiosis. N Engl J Med. Jul 15 1999;341(3):148-55. [Medline].
Aguero-Rosenfeld ME, Horowitz HW, Wormser GP, et al. Human granulocytic ehrlichiosis: a case series from a medical center in New York State. Ann Intern Med. Dec 1 1996;125(11):904-8. [Medline].
Bakken JS, Dumler JS, Chen SM, et al. Human granulocytic ehrlichiosis in the upper Midwest United States. A new species emerging?. JAMA. Jul 20 1994;272(3):212-8. [Medline].
Heilpern KL. Update: human ehrlichiosis--Maryland and Wisconsin, 1994. Ann Emerg Med. Jul 1998;32(1):108-10. [Medline].
Lovrich SD, Jobe DA, Kowalski TJ, Policepatil SM, Callister SM. Expansion of the midwestern focus for human granulocytic anaplasmosis into the region surrounding la crosse, wisconsin. J Clin Microbiol. Nov 2011;49(11):3855-9. [Medline].
Pritt BS, Sloan LM, Johnson DK, Munderloh UG, Paskewitz SM, McElroy KM, et al. Emergence of a new pathogenic Ehrlichia species, Wisconsin and Minnesota, 2009. N Engl J Med. Aug 4 2011;365(5):422-9. [Medline].
Strle F. Human granulocytic ehrlichiosis in Europe. Int J Med Microbiol. Apr 2004;293 Suppl 37:27-35. [Medline].
Hamburg BJ, Storch GA, Micek ST, Kollef MH. The importance of early treatment with doxycycline in human ehrlichiosis. Medicine (Baltimore). Mar 2008;87(2):53-60. [Medline].
Everett ED, Evans KA, Henry RB, McDonald G. Human ehrlichiosis in adults after tick exposure. Diagnosis using polymerase chain reaction. Ann Intern Med. May 1 1994;120(9):730-5. [Medline].

Female Lone Star tick, Amblyomma americanum, found in the southeastern and Midatlantic United States. It is a vector of several zoonotic diseases, including human monocytic ehrlichiosis and Rocky Mountain spotted fever. Courtesy of the CDC/Michael L. Levin, PhD.

Map of the United States showing the distribution of the Lone Star Tick, which is the principle vector for ehrlichiosis.

Established and reported distribution of anaplasmosis vectors Ixodes scapularis and Ixodes pacificus, by county, in the United States from 1907-1996. Courtesy of the Division of Vector-Borne Infectious Diseases at the Centers for Disease Control and Prevention.

Anaplasmosis incidence by age. Courtesy of the Centers for Disease Control and Prevention.

Ehrlichiosis incidence by age. Courtesy of the Centers for Disease Control and Prevention.

Table. Characteristics of HME Versus HGA

Table. Characteristics of HME Versus HGA

	Human monocytic ehrlichiosis (HME)	Human granulocytic anaplasmosis (HGA)
Cell type Affected	Monocytes	Granulocytes
Organism	E chaffeensis	A phagocytophilum
Vector	Amblyomma americanum (Lone Star tick)	Ixodes scapularis (black-legged tick), Ixodes pacificus (Western black-legged tick) in California, Ixodes ricinus in Europe, and probably Ixodes persulcatus in parts of Asia
Location	Southeastern and south-central United States	Wisconsin and Minnesota, less active in New York and Connecticut, also California
Rash	30% of adults, 60% of children	Rare
Prognosis	~3% mortality	< 1% mortality

View Table List

Read more about Ehrlichiosis on Medscape