The incidence rate of babesiosis in Maine, Vermont, and New Hampshire saw a dramatic increase over a multiyear period and saw an increase overall in other states where the disease is endemic.
The CDC is reporting that babesiosis, a zoonotic-tickborne parasitic disease, has increased dramatically in 3 states (Maine, Vermont, and New Hampshire). Over a study period of 2011-2019, Vermont saw an increase of 1,602%, from 2 to 34 cases, Maine saw an increase of 1,422%, from 9 to 138 cases, and New Hampshire 372%, from 13 to 78 cases.
This is significant because those 3 states were not considered to have endemic babesiosis, and now the CDC has reclassified them as such.
Seven other states that were known for endemic transmission of the disease, including, Connecticut, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Wisconsin, saw increased case counts as well. Specifically, incidence rates increased significantly in Connecticut, Massachusetts, New Jersey, New York, and Rhode Island (p<0.001).
The report was published in the most recent MMWR.
In the US, the disease is carried by intraerythrocytic Babesia parasites, with most babesiosis cases are caused by Babesia microti, transmitted from bites of blacklegged (deer) ticks, Ixodes scapularis, in northeastern and midwestern states, according to the CDC report.
Tickborne disease in the United States overall has increased 25% from 2011 to 2019 with 40,795 cases reported in 2011 and 50,856 in 2019.1 Although the overall number of babesiosis cases is low, the increase, especially in new geographic areas suggests the habitat of the blacklegged ticks—which are mostly responsible for the disease—is spreading.
With this report, clinicians and the general public are reminded to use precautions when out in nature during the warmer months in the northeast and the midwest where the greatest prevalence of the disease is seen. Safety considerations for the public include people wearing long pants and hats, avoiding underbrush and long grass, and using tick repellents before going outside. And, after being outdoors in these and wooded areas, clothes should be removed and inspection for ticks in exposed skin areas and people’s scalps should be made. If a tick has been spotted on an individual, and it looks like a bite, or a tick is still burrowed into the skin, a health care provider should be contacted right away.
Both the public and health care providers in states with endemic babesiosis and bordering states should be aware of the clinical signs of babesiosis and risk factors for Babesia infection. CDC says signs of infection include:
Babesiosis can be dangerous or even fatal, especially in individuals who are immunocompromised or asplenic. Patients diagnosed with the disease can be treated with antibiotics.
For clinicians, babesiosis is a reportable condition in many states, and the FDA recommends blood donation screening for babesiosis in 14 states and the District of Columbia. Now with this report, Maine, New Hampshire, and Vermont are also included on the list of states recommended for blood donor screening.
The report’s authors acknowledge 3 limitations to the data. “First, babesiosis is not reportable in all states; for example, although transmission of B microti has been documented in Pennsylvania, babesiosis is not a reportable condition in that state. Second, these data probably do not represent all incident cases of babesiosis in reporting states. Patients with nonspecific symptoms might not be tested for babesiosis. Finally, cases are reported by the patient’s state of residence and might not always reflect the location where transmission occurred,” they wrote.
1. CDC. Ticks: tickborne disease data surveillance summary. Atlanta, GA: US Department of Health and Human Services, CDC; 2021. https://www.cdc.gov/ticks/data-summary/index.html