Ehrlichiosis

Causative Agent

Ehrlichia chaffeensis & Ehrilichia ewingii

Type of Organism

Rickettsia Bacterial Species

Length of Attachment for Transmission

18-24 Hours

Initial Symptoms

Symptoms may begin 1-2 weeks after exposure. Symptoms include:

• Chills, sweats, headache, fatigue, nausea, diarrhea, vomiting, and fever.
• Joint and muscle pain
• Disorientation, rash, and eye infection.

Immunocompromised individuals are at a greater risk for more severe symptoms which include trouble breathing and kidney dysfunction.

Headache and fatigue may continue for a few weeks after treatment.

Diagnosis and Testing

• The use of Polymerase Chain Reaction (PCR) to detect Ehrlichia DNA in the blood can be used for diagnosis and should be performed within the first week of infection.
• Visualization of peripheral blood smears under a microscope may show Ehrlichia in white blood cells confirming diagnosis.
• When testing for antibodies specific to Ehrlichia, Indirect Immunofluorescence Assays (IFA) are performed on two samples. The first sample is collected within 7 days of infection and will be compared to the second sample collected 2-4 weeks after infection.
• Ehrlichiosis will be diagnosed if the second sample shows the number of antibodies present has increased since the first sample was tested.
• A false negative is possible in the first 7-10 days of illness and will commonly occur when the first sample is tested.
• Blood test results of low platelet count, low white blood cell count or elevated liver enzyme levels can assist with diagnosis.

CDC Treatment Recommendation

• Adults: Doxycycline 100mg-2x daily for 7-14 days.
• Children: 2.2mg/kg-2x daily for 7-14 days

Disease Pathogenesis

Ehrlichia chaffeensis is the causative agent of Human Monocytic Ehrlichiosis. Once inside the host, Ehrlichia chaffeensis will invade white blood cells known as monocytes. The immune system will respond to this invasion by destroying the infected host cells directly causing disease symptoms.

Ehrlichia ewingii is the causative agent of Human ewingii Ehrlichiosis. Once inside the host, Ehrlichia ewingii will invade white blood cells known as neutrophils/granulocytes. The immune system will respond to this invasion by destroying the infected host cells directly causing disease symptoms.