Blacklegged Tick

Anaplasmosis is a tickborne disease caused by bacteria called Anaplasma phagocytophilum. It is spread by the bite of an infected blacklegged tick, the same tick that transmits Lyme disease, babesiosis, Borrelia miyamotoi and Powassan virus. It is also possible for Anaplasma phagocytophilium to be transmitted through blood transfusions.

Anaplasmosis is the second most commonly reported tickborne disease in Vermont. In the last five years, the number of reported anaplasmosis cases has increased substantially. Since 2015, Vermont has had the highest annual incidence of anaplasmosis in the U.S.

The best way to prevent anaplasmosis is to prevent tick bites. If you find a tick on your body, remove it quickly to reduce the risk of contracting anaplasmosis. See a health care provider if you do get sick. Anaplasmosis is curable but it can also be a serious, and sometimes fatal, disease.


The symptoms of anaplasmosis usually begin five to 21 days following a tick bite and can include:

  • Fever
  • Chills
  • Headache
  • Malaise
  • Muscle pain
  • Cough
  • Confusion
  • Nausea
  • Vomiting

Unlike Lyme disease, anaplasmosis does not commonly cause a rash. In fact, only 10% of Vermonters with anaplasmosis report having a rash. The most common symptoms reported in Vermont residents include fever, malaise, muscle aches and headaches.

Symptoms of Anaplasmosis

People with anaplasmosis may also develop anemia, low white blood cell counts, low platelet counts, and elevated liver enzymes.

Anaplasmosis can be a serious illness. Thirty-six percent of cases in Vermont are hospitalized for their illness. And if not treated correctly, anaplasmosis can be fatal.

Who is at risk in Vermont?

Anyone can get anaplasmosis, but older individuals and those with compromised immune systems are most at risk.

In Vermont, males appear to be more at risk for anaplasmosis than females. For both genders, the risk begins to increase for middle-aged adults and continues to rise until individuals reach their early 80’s.

Age Distribution for Anaplasmosis in Vermont 2015
Trends Over Time

Anaplasmosis has become an increasingly common tickborne disease in Vermont. Between 2008 and 2010, 3 or fewer cases were reported in Vermont each year. But beginning in 2011, the number of reported cases began rising. Case counts have increased each year since then, culminating in 201 reported cases in 2016, the latest year that data are available.

What time of year are Vermonters at risk for Anaplasmosis?

Like Lyme disease, the risk for contracting anaplasmosis is relatively low in the winter, increases in the spring and peaks in early summer. The risk decreases slightly in the late summer. Unlike Lyme disease, the risk for anaplasmosis increases once again in the autumn.

Risk of Anaplasmosis in Vermont

Anaplasmosis can only be diagnosed by a health care provider. The symptoms of anaplasmosis can be non-specific and vary from person-to-person, making diagnosis difficult, though blood tests can be helpful.

To learn more about diagnosing anaplasmosis, please visit the CDC website.


Anaplasmosis can be treated with antibiotics. Early treatment is important for avoiding more severe complications from anaplasmosis.

To learn more about the treatment for anaplasmosis, please visit the CDC website.