Babesiosis in Vermont is caused by an infection with a microscopic blood parasite called Babesia microti. These parasites can be transmitted to humans by the bite of infected blacklegged ticks (Ixodes scapularis), the same tick that transmits Lyme disease and anaplasmosis. Babesiosis can also be transmitted by blood transfusion and rarely by congenital transmission, from an infected mother to her baby (during pregnancy or delivery).

Symptoms

Many people who have been infected with Babesia do not experience any symptoms.

When symptoms do occur, they typically begin one to four weeks after a tick bite and can include fever, chills, sweats, headache, body aches, loss of appetite, nausea, or fatigue. Babesiosis can also cause a type of anemia, which makes a person develop jaundice (yellowing of the skin) and dark urine.

Anyone can get sick with babesiosis, but people who have compromised immune systems, kidney or liver disease, those who do not have a spleen, and older adults are at greater risk for serious complications, including death.                

Babesiosis can be diagnosed using blood tests. The disease can be successfully treated with the appropriate medical care.

Vertical column chart depicting reported signs and symptoms of babesiosis during 2013-2022. 90% of patients reported malaise/fatigue and 80% reported fever. The least commonly reported symptom is proteinuria (abnormally high levels of protein in urine) at 48%.

Who is at Risk in Vermont?

Anyone can get babesiosis, however, 70% of cases reported to the Health Department are in Vermonters 55 years of age or older. Most cases have occurred in residents of the state’s southern-most counties: Bennington, Rutland, Windsor and Windham.

Column chart depicting the incidence rate (cases per 100,000 people) of babesiosis in Vermont by age group and sex during 2013-2022. Vermonters over 55 years of age had the highest rates of babesiosis.
Map of Vermont by county, shaded from dark to light blue to reflect the number of cases of babesiosis per 100,000 people in 2022. Windsor County had the highest number of cases at n=31

Trends over Time

Babesiosis is the third most common tickborne disease in Vermont. Yearly reported cases of babesiosis in Vermont increased from two cases in 2011 (incidence = 0.3 per 100,000 population) to 34 cases in 2019 (5.4 per 100,000 population), a 1,602% increase in incidence. 

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

column chart depicting the number of confirmed and probable cases of babesiosis by year during 2013-2022. 2022 had the highest number of confirmed and probable cases at n=60.

When are Vermonters at Risk?

People may be at risk for babesiosis whenever blacklegged ticks are active, but most cases are reported in June through August.

Column chart depicting babesiosis cases by month of illness onset in Vermont during 2013-2022. July had the highest number of cases at n=50

Preventing Babesiosis 

The best way to prevent babesiosis is to prevent tick bites.

Topics:
Outdoor Safety | Tickborne Diseases
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