Disease Caused by Tick Bites Spreading in Northeast

A tick-borne parasitic disease has claimed new ground in the Northeast, having been announced as being "endemic" in three more states.

According to a Morbidity and Mortality Weekly Report published on March 17 by the U.S. Centers for Disease Control and Prevention (CDC), cases of babesiosis spiked between 2011 and 2019, with 16,456 cases being reported across 37 states. Nearly all of those cases occurred in 10 mostly Northeast states: Connecticut, Maine, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Rhode Island, Vermont and Wisconsin.

Babesiosis was previously considered endemic and a regular infection risk in seven of those states, but has been newly classified as endemic in Maine, New Hampshire and Vermont.

"Babesiosis is a disease that can be transmitted to humans by the bite of a tick that is infected with a Babesia parasite," Kirsten Crandall, a tick-borne disease researcher and Ph.D. candidate at McGill University, told Newsweek. "This parasite affects humans by infecting their red blood cells. Three different species of Babesia have been shown to infect humans in the United States and Canada, which include Babesia microti, Babesia duncani and Babesia odocoilei."

deer tick on skin
Stock image of a deer tick (Ixodes scapularis) on human skin. A parasitic disease called babesiosis spread by the ticks has become endemic in three U.S. states, with cases on the rise. iStock / Getty Images Plus

These protozoan parasites live inside ticks, and are transferred into hosts when the ticks bite them.

"It is transmitted by Ixodes scapularis (black-legged tick or deer tick), but infection can also be rarely acquired through contaminated blood products or organ transplantation," Rami Waked, a doctor at Maine Medical Center, told Newsweek.

The parasite is most commonly spread during the tick's nymph life stage in spring and summer, when the tick is most active.

"An infected tick is required to remain attached for at least 36 hours for the Babesia parasite to be efficiently transmitted. However, humans that become infected may not always recall a tick bite," Crandall said.

white-footed mouse
Stock image of a white-footed mouse. These mammals are the usual hosts for Ixodes scapularis, the ticks that carry parasites for a disease called babesiosis that has become endemic in three U.S. states. iStock / Getty Images Plus

Its usual non-human hosts are small mammals found across most of the U.S.

"The main reservoirs for the parasite in nature are the white-footed mice and meadow voles," Alvaro Toledo, an assistant professor of entomology at Rutgers University, told Newsweek. "Immature stages of the black-legged tick feed on these animals and acquire the pathogen that can be subsequently passed to humans during feeding."

Symptoms usually appear 1 to 4 weeks following a tick bite, and can vary from person to person.

"The disease courses initially like a febrile illness with flu-like symptoms [fever, chills, headache, body aches, loss of appetite or fatigue]. This parasite infects human red blood cells, growing and dividing asexually and therefore causes a particular type of anemia called hemolytic anemia that can lead to jaundice [skin becomes yellowish]," Toledo said.

Some people infected with babesiosis do not have any symptoms, while others might experience severe symptoms, especially those that are immunocompromised, do not have a spleen, elderly or have another serious health conditions (e.g., liver or kidney disease).

"Each case is individual, which may present a different set of symptoms. In certain cases, the disease can be severe and life-threatening, as it affects the red blood cells," Crandall said.

babesiosis parasite red blood cells
Stock illustration of Babesi microti, the parasite that causes the disease babesiosis, inside a red blood cell. iStock / Getty Images Plus

The reason for cases increasing and becoming endemic in new areas might be because the range of the parasite's tick vector is also expanding across the Northeast.

"It has been endemic in many states in the Northeast for years," Toledo said. "What we are witnessing is an expansion of the endemic in areas. This is actually not surprising since we know that the vector, the black-legged tick, is expanding throughout the Northeast.

"One can expect to see more cases of human babesiosis, particularly in new areas. Physicians should be aware of the presence of human babesiosis to diagnose and treat patients promptly, particularly those that are at higher risk."

Becoming endemic in new areas means that increasing numbers of people will be infected by the parasite.

cdc figure of babesiosis range
Average number of reported babesiosis cases (left) and average babesiosis incidence (right) by state in the U.S. from 2011 to 2019. Left: cases classified by state of residence (16,456) and right: cases per 100,000 population. U.S. Centers for Disease Control and Prevention

"When something becomes endemic, it means that it becomes more readily available within that area be it a tick or a pathogen [e.g., parasite, bacteria, virus, etc.]. As a result of a greater number of ticks may carry this parasite, it means that a greater number of individuals may become infected with babesiosis in the future," Crandall said.

It might also mean that individuals could have a greater chance of co-infections in the future, meaning that an individual could be infected with babesiosis and another tick-borne disease, such as Lyme, at the same time.

"A rise in babesiosis cases may also affect the blood supply, as this parasite can be transmitted via blood transfusions," Crandall said. "Blood centers that are located in the endemic regions of the Northeast may become impacted if a greater number of cases of Babesia are detected in blood transfusions.

The best way to prevent contracting the disease is to keep free of tick-infested vegetation such as brush and wooded areas.

tick in grass
Stock image of a tick in long grass. iStock / Getty Images Plus

"Recreational, occupational and residential habits make it difficult to avoid tick exposure for most people living in endemic areas," Peter Krause, a senior research scientist in epidemiology at Yale School of Public Health and Yale School of Medicine, told Newsweek. "Ticks are often present in grassy areas and in leaf litter on personal property and can attach during even brief exposure. Use of repellents is very helpful in preventing tick bites."

Someone can also minimize risk by wearing long sleeves and pants in grassy areas, and keeping lawns mowed.

"The repellent DEET [N,N-diethyl-m-toluamide, or N,N-diethyl-3-methylbenzamide] is the most effective." Krause said. "Permethrin is a highly effective acaricide that can provide additional protection. Permethrin repellent can be applied to, or impregnated in, clothing and shoes."

If you have entered an area where ticks might be present, make sure to check your body for ticks afterward, or take a shower.

"Tick checks under bright lighting should be performed at the end of each day of exposure," Krause said. "Use of a washcloth or tweezers with special attention to armpit, groin, back and scalp areas may dislodge attached and unattached ticks. Studies have demonstrated that early removal of an Ixodes tick minimized the risk for acquiring B. burgdorferi infection."

If you find a tick, remove it from your body as soon as possible.

"A tick should be removed with an ordinary pair of thin-tipped tweezers or forceps," Krause added. "The tick should be grasped by the mouth end and gently pulled straight upward."

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about tick-borne diseases? Let us know via science@newsweek.com.


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