Ehrlichiosis Anaplasmosis

Template:Helvetica Spotted Fever Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Overview

Ehrlichiosis diseases are caused by the Ehrlichial species of bacteria, E. chaffeensis, E.muris, and E. ewingii. The Ehrlichial bacteria that cause human infection are most often transmitted by the lone star tick (amblyomma americanum.) The disease begins with an incubation period of 1-2 weeks post inoculation, followed by typical disease symptoms (fever, headache, fatigue, and muscle aches). Diagnosis is based on clinical presentation of symptoms, especially if a recent tick bite is noted. Confirmation of the disease may be done with laboratory testing. Doxycycline is often the first line treatment for individuals of all ages.

Classification

• A rash associated with Ehrlichiosis may often be misdiagnosed as Rocky Mountain Spotted Fever. The rash may differentiate from RMSF in presentation if it presents itself as Erythroderma (a sunburn-like rash).
• Ehrlichiosis may also me misdiagnosed as the following tick-borne diseases:

• Within the disease, the two species may be differentiated based on the location of the infection.

• The most effective way to differentiate is by laboratory testing.

Epidemiology and Demographics

• Annual reported cases of Ehrlichiosis have been consistently rising in the United States since 1996.

Risk Factors

• Tick bites are the most potent risk factor when contracting Ehrlichiosis.
• Tick bites are more likely to occur during seasons of heightened tick activity, including the spring and summer months. However tick bites may occur year round.

Diagnosis

Symptoms

The following is a list of common symptoms associated with Ehrlichiosis, however individuals may present symptoms differently. Therefore each patient should be individually evaluated for a potential combination of Ehrlichiosis symptoms.

• Fever
• Malaise (generally feeling sickly)
• Chills
• Muscle Pain
• Nausea
• Headache
• Vomiting
• Diarrhea
• Confusion
• Conjuctival injection (pink eye)
• Rash

Rash

The Ehrlichiosis rash may occur with a few different types of features:

• The rash may appear maculopapular or petechial.
• A rash that may be associated with Ehrlichiosis is not usually itchy.
• Does not usually appear of the face, though it may appear on palms and soles.
• Erythroderma, a sunburn like rash, may appear within a few days of symptoms onset.
• Ehrlichiosis rashes may resemble those of Rocky mountain spotted fever. Therefore laboratory tests may be required to differentiate Ehrlichiosis from other tick-borne diseases.

Laboratory Findings

Polymerase Chain Reaction

• Most accurate results are discovered within the first week of illness.
• Finding may indicate negative results, yet infection may still be present.

Peripheral Blood Smear

• A microscopic examination of the blood may reveal microcolonies of ehrlichiae.
• This method enables differentiation between the species of infection:
  • E. chaffeensis usually infects monocytes
  • E. ewingii coomonly infects granulocytes

Serologic Testing

• Most often an Immunofluorescence assay (IFA).
• Two tests are performed. The first upon initial signs of infection. The second after 2-4 weeks of infection.
• Original tests may reveal negative results; however, later testing will reveal a significant increase in the bacterial load.
• Antibodies may remain high for many months after the disease is resolved. Thus multiple tests should be conducted in order to monitor a resolution of the disease.

Treatment

Medical Therapy

• Treatment is most effective during the early course of the disease.
• If Ehrlichiosis is suspected a regimen of Doxycycline is administered for 7 to 14 days.

Doxycycline:

• Adult- 100mg every 12 hours

Children (under 100lbs) 2.2 mg/kg of body weight, twice a day.

Prevention

• Avoiding tick bites and endemic regions are the best methods in avoiding Ehlichiosis.