Study reveals emerging cases of babesiosis in Mid-Atlantic region

A recently published study in the Journal of Medical Entomology has shed light on the emergence of babesiosis in the Mid-Atlantic region, documenting human cases and the presence of Babesia microti in local tick populations.

The study, titled “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,” offers a comprehensive analysis of the escalating public health threat posed by this tick-borne disease.

The study confirms the expansion of babesiosis from its historical concentration in the Northeast and Upper Midwest to the Mid-Atlantic region. It highlights a rising number of locally acquired (autochthonous) human cases and the identification of Babesia microti, the primary causative agent of human babesiosis, in blacklegged ticks (Ixodes scapularis) and Ixodes keiransi ticks.

The research was conducted by Ellen Stromdahl, Ph.D., a retired entomologist at the Vector-Borne Disease Laboratory, Defense Centers for Public Health-Aberdeen, along with 21 colleagues from various institutions and departments.

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 emphasize the necessity for heightened surveillance, public awareness, and preventive measures against tick-borne diseases in the Mid-Atlantic region,” states Stromdahl. “Healthcare providers should consider babesiosis in the differential diagnosis for patients with febrile illness, especially during peak tick-activity seasons.”

Babesiosis, caused by microscopic parasites that infect red blood cells, can vary from asymptomatic to severe illness, particularly in immunocompromised individuals. It can be especially severe in the elderly or immunocompromised, particularly when concurrent infections with Borrelia burgdorferi (the bacteria that causes Lyme disease) occur.

Diagnosing babesiosis can be challenging due to its rarity and early symptoms that mimic conditions more commonly seen in elderly populations or associated with other tick-borne diseases. This can lead to misdiagnosis or empirical treatment with antibiotics typically prescribed for Lyme disease or anaplasmosis, such as doxycycline. However, antibiotics alone are ineffective against babesiosis, underscoring the importance of early and accurate diagnosis.

Furthermore, coinfection of Ixodes scapularis with B. microti and B. burgdorferi is prevalent. In the 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. Additionally, additional I. scapularis from Maryland and Virginia were found concurrently infected with A. phagocytophilum, B. burgdorferi, B. microti, and Borrelia miyamotoi. Practitioners must be vigilant for concurrent infections that may complicate diagnosis and treatment.

This research underscores the significance of enhanced public health surveillance, including thorough investigations of potential human babesiosis cases and tick surveillance whenever feasible.

Educating medical providers, public health practitioners, and the general population about this emerging risk, including prevention strategies, symptom recognition, and appropriate treatment, is crucial.