Anaplasmosis is a tick bite illness caused by the bacterium Anaplasma phagocytophilum. It is spread by the bite of infected blacklegged ticks, the same tick that transmits Lyme disease, babesiosis, hard tick relapsing fever, and Powassan virus. It is also possible for Anaplasma phagocytophilum to be transmitted through blood transfusions and organ transplants.

Anaplasmosis is the second most common tick bite illness 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 anaplasmosis and other tick bite illnesses. See a health care provider if you get sick. Anaplasmosis is treatable but it can be a serious and sometimes fatal disease.

Symptoms

Symptoms of anaplasmosis usually begin five to 21 days after 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 9% of Vermonters with anaplasmosis report having a rash. The most common symptoms reported in Vermont residents with anaplasmosis include fever, malaise, muscle aches, chills and headaches.

Vertical column chart depicting the most commonly reported signs and symptoms of patients with anaplasmosis during 2013-2022. 100% of patients reported a fever and 87% of patients reported malaise. Nausea was the least commonly reported symptom at 38%.

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. If not detected and treated promptly, anaplasmosis can be fatal in older patients and people with other health problems.

Who is Most at Risk?

Anyone can get anaplasmosis, but older adults and people with compromised immune systems are most at risk. In Vermont, anaplasmosis affects older adults and males more commonly than females.

Column chart depicting the incidence of anaplasmosis (per 100,000 people). Older males have a higher incidence of anaplasmosis compared to female in nearly every age group. Data is from 2013 to 2022.

Trends over Time

Anaplasmosis has been reported more frequently in Vermont. During 2008-2010, three or fewer cases were reported each year. Case counts have increased since 2011, with the highest number of cases reported in 2022. 

Case numbers are low in 2020 and 2021 due to decreased reporting during the COVID-19 pandemic.

Column chart displaying confirmed and probable cases of anaplasmosis in Vermont between 2013 and 2022. 2022 saw the highest number of cases at n=572.

 

When are Vermonters at Risk?

Like Lyme disease, the risk for contracting anaplasmosis is highest during summer months. However, unlike Lyme disease, the risk for anaplasmosis increases again in the fall.

Column chart depicting anaplasmosis cases by month of illness onset, 2013-2022. June had the highest number of cases.

Where is the Risk Highest in Vermont?

While people can get become sick with anaplasmosis anywhere in the state, cases are most commonly reported from southern counties. Windsor County saw the highest number of anaplasmosis cases in 2022.

Map of Vermont by county, shaded dark to light blue to display the cases of anaplasmosis per 100,000 people in 2022. Windsor County had the highest number of cases

Diagnosis

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 it difficult to recognize, but blood tests can help with diagnosis. If your health care provider suspects anaplasmosis or another tick bite illness, they may prescribe antibiotics while you wait for results. Learn more from the CDC.

Treatment

Anaplasmosis can be treated with antibiotics. Early treatment is important for avoiding more severe complications from anaplasmosis. Doxycycline is the recommended antibiotic treatment for anaplasmosis in adults and children of all ages. Learn more from the CDC.

Topics:
Outdoor Safety | Tickborne Diseases
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