Baltimore Emerges as Hotspot for Dangerous Tick-Borne Parasite

A potentially life-threatening parasitic infection previously confined to the northeastern United States has established a foothold in the Baltimore region, with researchers identifying the city as a “hotspot” for babesiosis, a tick-borne disease that can cause severe anemia and even death in vulnerable populations.

Babesiosis, a malaria-like illness carried by blacklegged ticks (also known as deer ticks), has been steadily expanding its range southward into the mid-Atlantic states, according to a comprehensive study published in the Journal of Medical Entomology that tracked the parasite’s spread over the past decade.

Baltimore Region Shows Highest Concentration

“Baltimore is a hotspot,” warned Ellen Stromdahl, a retired tick researcher from the Defense Centers for Public Health at U.S. Army Aberdeen Proving Ground who helped lead the groundbreaking study, as reported by The Baltimore Banner.

While the total number of cases remains relatively small compared to Lyme disease—the Maryland Department of Health identified only 29 infections statewide in 2023—researchers believe these figures represent just “the tip of the iceberg,” with many cases likely going undiagnosed. By comparison, Maryland reported 2,463 cases of Lyme disease during the same period.

The research team, which included 21 tick experts from across the eastern United States and South Africa, collected and tested over 1,300 ticks from Delaware, Maryland, and Virginia. They discovered the Babesia microti parasite in all three states, with two distinct hotspots emerging: the Baltimore metropolitan area and the Delmarva Peninsula.

Climate Change Driving Expansion

“The results of the study reveal that the Babesia parasite is rapidly expanding through the mid-Atlantic. This shift, which has coincided with changing weather patterns, could pose a serious threat to people in communities where the disease has long been considered rare,” according to reporting by Grist.

Researchers attribute the parasite’s southward expansion primarily to climate change, which has created increasingly favorable conditions for tick populations to thrive in regions previously inhospitable to them. Warmer-than-average winters, occurring with greater frequency in recent years, have allowed ticks to remain active for longer periods and expand their geographic range.

The Johns Hopkins Bloomberg School of Public Health notes that the spread of babesiosis follows a predictable pattern: “Areas that saw rising cases of Lyme disease from the 1980s to the early 2000s reported more babesiosis cases one to two decades later,” according to experts cited by Johns Hopkins University.

Dangers and Symptoms

The parasites that cause babesiosis invade red blood cells and can lead to a dangerous—or in rare cases, even fatal—level of anemia, according to the Centers for Disease Control and Prevention. While many infected individuals never develop symptoms, those who do typically experience fever, body aches, fatigue, and potentially more severe complications.

Older adults and people with compromised immune systems face the highest risk of developing serious illness. In severe cases, babesiosis can lead to respiratory failure, kidney failure, or even death. Prompt diagnosis and treatment with a combination of antiparasitic medications and antibiotics is essential for preventing complications.

“I’m more worried about ticks in Maryland than mosquitoes,” Dr. David Sullivan, a professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, told The Baltimore Banner, emphasizing the growing threat posed by tick-borne illnesses in the region.

Diagnostic Challenges

Experts warn that many healthcare providers in the mid-Atlantic region may not be familiar with babesiosis since it has historically been rare in the area. Patients with symptoms are often misdiagnosed with the flu or other common illnesses, delaying crucial treatment.

Complicating matters further is the fact that babesiosis can occur simultaneously with other tick-borne diseases. “Doctors may diagnose Lyme and prescribe antibiotics only, which will not knock out the parasites,” Stromdahl explained to researchers from Entomology Today.

Cases reported in the research study highlight this danger. An elderly patient in Virginia became severely ill before doctors identified babesiosis as the cause—he ultimately required a total blood exchange transfusion to survive after weeks of misdiagnosis, according to specialists familiar with the case.

Transmission and Prevention

Babesiosis is spread primarily through the bite of infected blacklegged ticks, which must typically remain attached for 24-36 hours to transmit the parasite. The disease can also spread through blood transfusions, which has prompted the Food and Drug Administration to recommend blood donation screening for babesiosis in states where the disease is prevalent.

Prevention measures mirror those for other tick-borne illnesses: wearing long sleeves and pants in tick-prone areas, using EPA-approved repellents, conducting thorough tick checks after outdoor activities, and promptly removing any attached ticks.

“If you see a tick and remove it within a day, you’re probably good,” Dr. Sullivan told The Baltimore Banner, emphasizing the importance of quick tick removal to prevent transmission.

Growing Concern for Public Health Officials

The discovery of Babesia-infected ticks throughout the region has prompted health officials to increase surveillance and consider expanded testing guidelines. According to a Maryland Department of Health report, monitoring for babesiosis has intensified as part of broader tick-borne disease surveillance efforts.

Researchers are urging healthcare providers in the Baltimore area and throughout the mid-Atlantic to consider testing for babesiosis in patients presenting with unexplained fever, fatigue, or flu-like symptoms, especially following potential tick exposure.

“These findings should serve as an early warning system,” Stromdahl emphasized. “We want to get the word out that the tick mix here now includes babesiosis, and doctors ought to order blood tests for those with symptoms and a tick bite. It could save their lives.”

As researchers continue to track the parasite’s spread, they caution that the current number of cases likely underrepresents the true extent of the problem, with many infections going undiagnosed or misdiagnosed due to low awareness among both the public and healthcare providers in newly affected regions.