Anaplasmosis is a disease caused by the bacterium Anaplasma phagocytophilum. The disease is spread by the bite of an infected black-legged tick, Ixodes scapularis, commonly known as the deer tick. This is the same tick that can transmit Lyme Disease. It is possible for a single tick to infect a person with both anaplasmosis and Lyme disease.


Symptoms of anaplasmosis are similar to those of the flu and can include:

  • Headache
  • Fever
  • Chills
  • Muscle aches
  • Fatigue

Less common symptoms are:

  • Abdominal pain
  • Nausea
  • Vomiting
  • Diarrhea
  • Joint aches
  • Rash

These symptoms appear five to 21 days following a tick bite and can last about one to two weeks.

Abnormal laboratory values associated with anaplasmosis include anemia, thrombocytopenia, leukopenia and elevated liver transaminases.


Anaplasmosis is treated with antibiotics. Most people experience mild illness and early treatment usually results in full recovery. People with weakened immune systems and those with underlying medical conditions may have more severe symptoms.

People at Risk

Individuals at greatest risk for getting anaplasmosis are those who spend time outside in wooded, brushy and grassy areas, including gardens. People are not always aware that they have been bitten by a tick, so let your health care provider know if you have spent time outside in these areas. Deer ticks are tiny and often go unnoticed. For example, nymphal deer ticks are about 2 millimeters in size.

While anyone can develop anaplasmosis, the disease tends to be most common in people who are older or have compromised immune systems.

When and Where Anaplasmosis Occurs

In the Northeast, most illness occurs during the spring and summer when the nymphal ticks are most active and people spend a lot of time outside. However, anaplasmosis can occur whenever deer ticks are active.

The first two human cases of locally-acquired anaplasmosis were reported in Vermont in 2010. Over the past few years, more cases have been reported, mostly from people who live in southern Vermont.


The best way to prevent anaplasmosis is to prevent tick bites

For more information on Anaplasmosis, visit the CDC Website