Ehrlichiosis and Anaplasmosis

Ehrlichiosis and anaplasmosis are diseases caused by bacteria and carried by ticks. Other names for these infections are:

  • Human monocytic ehrlichiosis (HME).

  • Human granulocytotropic anaplasmosis (HGA).

HME mostly occurs in the south-central and southeastern United States, where the lone star tick lives. However, infections have occurred in 47 states. HGA infections are limited to fewer geographic locations. Most cases are reported from southern New England, New York, New Jersey, Wisconsin, and Minnesota. This distribution is almost identical to that of Lyme disease because of the shared species of ixodid ticks (wood ticks, deer ticks).


  • HME is caused by Ehrlichia chaffeensis and other closely related ehrlichia bacteria.

  • HGA is caused by the bacteria Anaplasma phagocytophilum.

An infected adult tick transmits the infection by biting a human. Once a tick gains access to human skin, it generally climbs upward until it reaches a more protected area. This is often the back of the knee, groin, navel, armpit, ears, or nape of the neck. It then begins the slow process of embedding itself in the skin. Adult ticks are active during warmer times of the year. For this reason, most infections occur between late spring and early fall.


Many infected people have no symptoms. For those with symptoms, HME and HGA cause similar illnesses. Symptoms typically begin 1 week or more after a tick bite and may include:

  • Fever.

  • Headache.

  • Chills or shaking.

  • Fatigue.

  • Muscle pain.

  • Nausea.

  • Loss of appetite.

  • Vomiting.

  • Diarrhea.

Symptoms commonly last for 1 to 3 weeks if a patient is not diagnosed or not treated with an antibiotic. Extremely severe disease is rare, but occasional deaths from infection have been reported.


Diagnosis is suggested by a history of tick bites or potential exposure to ticks. Blood tests may show abnormalities of liver function and low counts of white blood cells and platelets. To confirm the diagnosis, the bacteria must be found in a smear of blood on a microscope slide or during testing of the liquid part of your blood (serum).


Treatment with an antibiotic is almost always effective in eliminating symptoms within a couple days and curing the infection.


Ticks prefer to hide in shady, moist ground. However, they can often be found above the ground clinging to tall grass, brush, shrubs, and low tree branches. They also inhabit lawns and gardens, especially at the edges of woodlands and around old stone walls. Within the normal geographic areas where HME and HGA occur, no vegetated area can be considered completely free of infected ticks. In tick-infested areas, the best precaution against infection is to avoid contact with soil, leaf litter, and vegetation as much as possible. Campers, hikers, field workers, and others who spend time in wooded, brushy, or tall grassy areas can avoid exposure to ticks by using the following precautions:

  • Wear light-colored clothing with a tight weave to spot ticks more easily and prevent contact with the skin.

  • Wear long pants tucked into socks, long sleeve shirts tucked into pants, and enclosed shoes or boots.

  • Use insect repellent. Spray clothes with insect repellent containing either DEET or permethrin. Only DEET can be used on exposed skin. Make sure to follow the manufacturer's directions carefully.

  • Wear a hat and keep long hair pulled back.

  • Stay on cleared, well-worn trails whenever possible.

  • Check yourself and others frequently for the presence of ticks on clothes. If you find one tick, there may be more. Check thoroughly.

  • Remove clothes after leaving tick-infested areas and, if possible, wash them to eliminate any unseen ticks. Check yourself, your children, and any pets from head to toe for the presence of ticks.

  • When attached ticks are found, you can greatly reduce your chances of getting HME and HGA if you remove them as soon as possible. Use a tweezer to grab hold of the tick by its mouth parts and pull it off.

  • Shower and shampoo after possible exposure to ticks.


Take your antibiotics as directed. Finish them even if you start to feel better.


  • You have a fever.

  • You develop a headache.

  • You develop fatigue.

  • You develop muscle pain.

  • You develop nausea, vomiting, or diarrhea.


  • Understand these instructions.

  • Will watch your condition.

  • Will get help right away if you are not doing well or get worse.