Ehrlichiosis

Overview

Ehrlichiosis is a reportable disease in Oklahoma.  Ehrlichiosis refers to diseases caused by bacteria in the genus Ehrlichia.  The diseases include human monocytotropic ehrlichiosis (HME), human granulocytotropic anaplasmosis (HGA) (formerly known as human granulocytotropic ehrlichisosis or HGE), and ehrlichiosis caused by Ehrlichia ewingii (E. ewingii).  HME is caused by the bacteria (Ehrlichia chaffeensis) following the bite of an infected lone star tick (Amblyomma americanum).  Lone star ticks are commonly found in Oklahoma, and are known to aggressively bite humans.  HGA is caused by the bacteria Anaplasma phagocytophila.  HGA is transmitted by the blacklegged tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus) primarily in the northeastern and western United States.  Amblyomma americanum is the primary tick vector of E. ewingii.  However, the ecological features of E. ewingii are not fully known.

The symptoms of ehrlichiosis will generally include a sudden onset of fever, chills, headache, myalgia, and fatigue within 5 to 10 days following a tick bite. The symptoms of ehrlichiosis are similar to Rocky Mountain spotted fever; however, a rash occurs less often. Other common symptoms include nausea, vomiting, abdominal pain, and loss of appetite. The severity of disease ranges from asymptomatic infection to death. Half of the people with ehrlichiosis require hospitalization. In persons with severely weakened immune systems, ehrlichiosis can result in a fatal overwhelming infection.

Treatment for ehrlichiosis with antibiotics (usually doxycycline) is very effective at reducing the severity of the disease. It is important antibiotic treatment for ehrlichiosis be started without delay when suspected. Overall, an estimated 2%-3% of persons with ehrlichiosis will die due to the infection. Although ehrlichiosis can be severe, preventive antibiotic therapy in non-ill persons following a tick bite is not recommended.

Laboratory testing for ehrlichiosis includes blood samples taken in the early stages of the illness (acute) and follow up (convalescent) specimens taken at least four weeks after the first specimen. Laboratory testing, though important, can take days to weeks for results to become available. If ehrlichiosis is suspected, it is important not to delay appropriate antibiotic therapy while waiting for laboratory confirmation. For additional information regarding laboratory testing for ehrlichiosis, view the Centers for Disease Control and Prevention lab site.

Please visit the following link for information tips on preventing tick bites and safe tick removal.

ADS Resources:
Ehrlichiosis Fact Sheet   En Espanol
Tickborne Disease Prevention

Other Resources:
CDC Ehrlichiosis
Tickborne Morbidity and Mortality Weekly Report Data

Surveillance Resources:
Ehrlichiosis Summary Data