Annapolis, MD; April 29, 2025 – A newly published study in the Journal of Medical Entomology provides critical insights into the emergence of babesiosis in the Mid-Atlantic region, documenting human cases and the presence of Babesia microti in local tick populations.
CDC states many people with Babesiosis do not feel sick and have no symptoms. However, some people might get flu-like symptoms, such as:
Fever, Chills, Sweats, Headache, Body aches, Loss of appetite, Nausea, Fatigue
Since the parasites attack red blood cells, babesiosis can lead to hemolytic anemia. Hemolytic anemia occurs when your red blood cells are destroyed faster than they can be replaced.
Babesiosis can become a serious, even life-threatening illness for certain people, especially those who: Do not have a spleen, Have a weak immune system for other reasons such as cancer, lymphoma, or HIV, Have serious health issues such as liver or kidney disease, Are older (> 50 years old).
Symptoms, if they appear, may start around a week after infection, but usually develop over a few weeks or months, or longer.
In the U.S. most Babesia infections are from blacklegged or deer tick (Ixodes scapularis) bites. Ticks are typically found in wooded, brushy, or grassy areas. Currently, most babesiosis cases occur in the Northeast and upper Midwest.
“Emerging Babesiosis in the Mid-Atlantic: Autochthonous Human Babesiosis Cases and Babesia microti (Piroplasmida: Babesiidae) in Ixodes scapularis (Acari: Ixodidae) and Ixodes keiransi (Acari: Ixodidae) Ticks from Delaware, Maryland, Virginia, West Virginia, and the District of Columbia, 2009-2024,” presents a comprehensive analysis of the growing public health threat posed by this tick-borne disease.
The study confirms that babesiosis, historically concentrated in the Northeast and Upper Midwest, is now expanding in the Mid-Atlantic region. The research highlights an increasing number of locally acquired (autochthonous) human cases and the detection of Babesia microti, the primary causative agent of human babesiosis, in blacklegged ticks (Ixodes scapularis) and Ixodes keiransi ticks.
The study was conducted by Ellen Stromdahl, Ph.D., retired entomologist at the Vector-Borne Disease Laboratory, Defense Centers for Public Health-Aberdeen, along with 21 colleagues from the Maryland Department of Health, Delaware Department of Natural Resources and Environmental Control, Old Dominion University, Delaware Technical Community College, Virginia Department of Health, University of Richmond, DC Health, U.S. Centers for Disease Control and Prevention, U.S. Food & Drug Administration, West Virginia Department of Health, and Mayo Clinic.
Key findings include:
- Autochthonous human babesiosis cases were reported for the first time from the Mid-Atlantic U.S. jurisdictions of Maryland, Virginia, West Virginia, and the District of Columbia between 2009 and 2024.
- Babesia microti was detected in ticks collected from Delaware, Maryland, Virginia, West Virginia, and DC.
- The study provides the first report of Ixodes keiransi as a potential vector of Babesia microti.
- The data suggest that babesiosis is becoming a growing concern in areas where it was previously considered rare or absent.
“The findings underscore the need for increased surveillance, public awareness, and preventive measures against tick-borne diseases in the Mid-Atlantic region,” says Stromdahl. “Healthcare providers should consider babesiosis in the differential diagnosis for patients with febrile illness, particularly during peak tick-activity seasons.”
Babesiosis, caused by microscopic parasites that infect red blood cells, can range from asymptomatic to severe illness, particularly in immunocompromised individuals. Babesiosis can be severe in the elderly or immunocompromised, especially when patients have concurrent infections with Borrelia burgdorferi (the bacteria that causes Lyme disease). Diagnosis can be difficult, as the disease is rare, and early symptoms of babesiosis resemble conditions more likely to be expected in elderly populations or associated with other more common tick-borne diseases.
As a result, babesiosis might be misdiagnosed or treated empirically with antibiotics typically prescribed for Lyme disease or anaplasmosis, such as doxycycline. However, antibiotics alone are not effective against babesiosis, making early and accurate diagnosis crucial.
Additionally, coinfection of Ixodes scapularis with B. microti and B. burgdorferi is common. In this study, half of the ticks positive for B. microti were also infected with B. burgdorferi, and one was triple-infected with Anaplasma phagocytophilum, B. burgdorferi, and B. microti. Further, additional I. scapularis from Maryland and Virginia were found concurrently infected with A. phagocytophilum, B. burgdorferi, B. microti, and Borrelia miyamotoi. Practitioners need to be alert to concurrent infections that might complicate diagnosis and treatment.
This research emphasizes the importance of enhanced public health surveillance, including conducting thorough investigations of all potential human cases of babesiosis and conducting tick surveillance whenever possible.
Education about this emerging risk, including how to prevent infection in the first place, how to recognize infection, and appropriate treatment, should be increased for medical providers, public health practitioners and the general population.
Babesiosis
- Babesiosis is caused by a microscopic parasite known as Babesia.
- Babesia parasites infect the red blood cells.
- The most common cause of babesiosis in humans in the United States is Babesia microti.
- In the United States, babesiosis most commonly occurs in the Northeast and upper Midwest.
Babesiosis is transmitted in nature by the bite of infected ticks
- Ixodes scapularis, also called the blacklegged (or deer) tick, transmits the infection in nature.
- I. scapularis can also transmit the bacteria that cause Lyme disease and anaplasmosis.
- Transmission can also occur in blood products such as blood transfusions.
Some, but not all, people with babesiosis develop symptoms
- When symptoms do occur, they usually appear 1 week to a few months after a tick bite.
- Some people develop nonspecific flu-like symptoms, such as fever, chills, sweats, headache, body aches, loss of appetite, nausea, or fatigue.
- Because Babesia parasites infect and destroy red blood cells, babesiosis can cause hemolytic anemia.
- Complications can occur and disease is most severe for the elderly, for individuals who are immunocompromised, and for those without a spleen.
Diagnosis and treatment
- The Babesia parasites can be seen in blood viewed under a microscope.
- There are other blood tests that can help diagnose babesiosis.
- See your doctor right away if you think you might have babesiosis.
- For ill patients, babesiosis usually is treated for at least 7-10 days with a combination of 2 drugs.
- Make sure you inform your doctor of any recent tick bites.
Keep Ticks Off
- Ticks are most active from late spring through early fall.
- Insect repellent containing 20–30% DEET is recommended to prevent tick bites.
- Repellents with up to 30% DEET can safely be used on children over 2 months of age.
- Treat clothes with permethrin (don’t use permethrin directly on skin).
- Long pants and long sleeves help keep ticks off of skin, and tucking pant legs into socks and shirts into pants keeps ticks on outside of clothing.
- Light colored clothing lets you spot ticks more easily.
- Talk to your veterinarian about tick control products for your pets.
- When enjoying the outdoors, be aware that wooded or brushy areas with tall grass and leaf litter are prime tick habitat. Walk in the center of the trail.
- Check yourself, your kids and your pets daily for ticks when spending time in tick habitat.
- Bathe or shower as soon as possible after coming indoors (within 2 hours) to wash off ticks.
To Remove Ticks
- Use fine-tipped tweezers.
- Grab the tick close to the skin; do not twist or jerk the tick.
- Gently pull straight up until all parts of the tick are removed.
- Wash your hands with soap and water or an alcohol-based rub.
- Clean the site of the tick bite with soap and water or an antiseptic.
- Do not use petroleum jelly, a hot match, nail polish, or other products to remove ticks.
CDC, Maryland Department of Health, The Journal of Medical Entomology publishes research related to all aspects of medical entomology and medical acarology, including the systematics and biology of insects, acarines, and other arthropods of public health and veterinary significance. For more information, visit https://academic.oup.com/jme, or visit www.insectscience.org to view the full portfolio of ESA journals and publications.
