EDGEWOOD, Md. — A potentially fatal tick-borne disease, once largely confined to New England, is now spreading into new territory. Babesiosis, caused by the parasite Babesia microti, has made its way south into the Mid-Atlantic states, including Maryland, Virginia, Delaware, Washington D.C., and West Virginia, prompting concern among scientists and health officials alike.
Unlike Lyme disease, babesiosis does not respond to standard antibiotics and can quickly escalate into a life-threatening condition if not diagnosed and treated correctly. As its range expands, many doctors in newly affected regions remain unprepared to recognize or manage the illness, raising serious public health concerns.
What Is Babesiosis?
Babesiosis is caused by a parasite that infects and destroys red blood cells. Early symptoms often mimic the flu—fever, chills, fatigue, muscle aches—but can escalate to jaundice, fainting, and even death in severe cases. Those over 65, immunocompromised, or without a spleen are especially vulnerable.
Transmission occurs through the bite of the blacklegged tick (Ixodes scapularis), also known as the deer tick—the same species that spreads Lyme disease.
Climate Change and Deer Populations Fuel Expansion
Lead researcher Ellen Stromdahl, a retired entomologist from the Defense Centers for Public Health-Aberdeen, attributes the parasite’s southward spread to multiple factors:
- Warmer winters from climate change have allowed ticks and their rodent hosts to survive and reproduce more effectively.
- Increased precipitation supports lush vegetation and habitat for ticks.
- Reforestation and white-tailed deer overpopulation have further helped ticks travel and settle into new areas.
“The deer don’t carry Babesia, but they transport the ticks that do,” Stromdahl explained.
New Study Reveals Alarming Spread
A comprehensive study published in the Journal of Medical Entomology outlines the expansion of babesiosis:
- Maryland reported its first locally-acquired case in 2009, followed by:
- Washington D.C. in 2013
- Virginia in 2016
- West Virginia in 2017
Researchers collected over 1,300 ticks between 2010 and 2024 in Delaware, Maryland, and Virginia. Of those, 2.7% carried B. microti. Certain hotspots had infection rates as high as 12.5%. Half of the infected ticks also harbored the Lyme disease bacterium, and one carried three pathogens: B. microti, Borrelia burgdorferi (Lyme), and Anaplasma phagocytophilum (anaplasmosis).
Hotspots Identified in Delmarva and Baltimore Metro
Two major outbreak regions emerged:
- The Delmarva Peninsula (spanning parts of Delaware, Maryland, and Virginia) accounted for 11 of 30 human cases.
- The Baltimore Metro Health District saw five cases between 2018 and 2022.
“Ticks that have been established longer in an area are more likely to carry Babesia,” Stromdahl said.…