Ehrlichiosis and Anaplasmosis Fact Sheet

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The Diseases and Transmission

  • Ehrlichia and Anaplasma are related bacteria that are transmitted by ticks. These bacteria infect white blood cells in humans.
  • There are three different bacteria that cause disease in humans:



Ehrlichia chaffeensis

Ehrlichia ewingii

Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila)



Human monocytic
ehrlichiosis (HME)

Ehrlichiosis ewingii

Human granulocytic
anaplasmosis (HGA, formerly HGE)

Tick Vector

Amblyomma americanum (lone star tick)

Ixodes scapularis (black-legged tick)

  • Animal reservoirs for E. chaffeensis and E. ewingii are white-tailed deer and dogs. The reservoirs for A. phagocytophilum include cattle, deer, and rodents. You cannot get the diseases directly from animals.
  • The diseases are not spread between humans other than through blood transfusions.
  • Maryland is home to both the lone star tick and the black-legged tick.

Symptoms and Treatment


Clinical Features

Ehrlichiosis ewingii

  • Symptoms appear 7 to 10 days after a tick bite.
  • Symptoms include fever, headache, muscle aches, nausea, vomiting, and loss of appetite.
  • Meningoencephalitis occurs in approximately 20% of cases.
  • Development of a rash is possible. This may be confused with Rocky Mountain spotted fever.


  • Symptoms appear 7 to 14 days after a tick bite.
  • Symptoms include fever, headache, and muscle aches.
  • Meningoencephalitis is rare.
  • Most infections occur when tick activity is highest, in late spring and summer.
  • If left untreated, HME and HGA may be severe.
  • Co-infection with more than one tick borne disease is possible.
  • The immune system is directly infected. Secondary infection and other complications can arise quickly.
  • The elderly and sick are more likely to develop severe illness.
  • Contact your health care provider if you develop any of these symptoms after a tick bite or after being in tick habitat. Your health care provider may order a blood test to help diagnose the disease.
  • The diseases are effectively treated with antibiotics, most commonly doxycycline.

Keep Ticks Off

  • Ticks are most active from late spring through early fall.
  • Insect repellent containing 20–50% DEET is recommended to prevent tick bites.
  • Repellents with up to 30% DEET can safely be used on children over 2 months of age.
  • Treat clothes with permethrin (don’t use permethrin directly on skin).
  • Long pants and long sleeves help keep ticks off of skin, and tucking pant legs into socks and shirts into pants keeps ticks on outside of clothing.
  • Light colored clothing lets you spot ticks more easily.
  • Talk to your veterinarian about tick control products for your pets.
  • When enjoying the outdoors, be aware that wooded or brushy areas with tall grass and leaf litter are prime tick habitat.
  • Check yourself, your kids and your pets daily for ticks when spending time in tick habitat.

To Remove Ticks

  • Use fine-tipped tweezers and protect bare hands with a tissue or gloves.
  • Grab the tick close to the skin; do not twist or jerk the tick.
  • Gently pull straight up until all parts of the tick are removed.
  • Wash your hands with soap and water or an alcohol-based rub.
  • Clean the site of the tick bite with soap and water or an antiseptic.
  • Do not use petroleum jelly, a hot match, nail polish, or other products to remove ticks.

For more information on tick borne diseases, visit: