Delaware, Maryland, Virginia Regions See Spread of Tick-Borne Malaria-Like Illness, Urgent Need for Increased Medical Awareness

A health alert has been issued in the U.S. Mid-Atlantic coastal region as 'Babesiosis,' a tick-borne disease, shows signs of rapid expansion. Concerns are mounting that the same blacklegged ticks that cause Lyme disease can also transmit Babesiosis, leading to urgent calls for increased disease awareness and early diagnostic efforts among healthcare professionals in the affected areas.

 
The Shadow of 'Babesiosis' Revealed by Jaundice Symptoms

In June 2023, Albert Duncan, in his mid-80s, suddenly collapsed at a garden party on the Virginia coast. His usual energetic and healthy demeanor heightened concerns among those around him. Dr. Ellen Stromdahl, an entomologist at the U.S. Army Public Health Center, suspected jaundice when she observed Duncan's skin had taken on a yellowish hue after he collapsed.

Duncan underwent numerous blood tests over several days, shuttling between emergency rooms, but all common age-related conditions like heart disease, diabetes, and and pneumonia tested negative. At Dr. Stromdahl's suggestion, Duncan's wife, Nancy, requested a test for Babesiosis, a rare malaria-like illness caused by microscopic parasites, and to their surprise, it came back positive. Additionally, Lyme disease, a much more common illness transmitted by the same tick, was also confirmed positive.

Had Duncan's doctors detected the infection earlier, treatment would have been possible with a combination of oral antibiotics and antiparasitic drugs. However, weeks after the onset of his symptoms, Duncan ultimately required a procedure called exchange transfusion. Medical staff drew all of his infected blood and replaced it with new blood. Approximately two weeks after the garden party, Duncan was able to recover his health.

 
Unusual Spread of a Rare Disease, The Starting Point of Research

According to the U.S. Centers for Disease Control and Prevention (CDC), Babesiosis is a rare disease, with only about 2,000 cases reported annually in the United States. However, the fact that Duncan contracted Babesiosis in Virginia was even more unusual, as there had been only 17 locally acquired cases in Virginia from 2016 to 2023.

Duncan's case led Dr. Stromdahl to question whether Babesiosis was becoming more common in Virginia and neighboring states. For the next two years, she collaborated with 21 tick research teams across the Eastern U.S. and South Africa to evaluate the prevalence of Babesia microti, the parasite that causes Babesiosis, in ticks and humans in these states from 2009 to 2024.

Her research findings, published in the Journal of Medical Entomology in April 2024, suggest that the Babesia parasite is rapidly spreading through the Mid-Atlantic region. This shift coincides with changing weather patterns and warns of a serious threat to communities where the disease was previously considered rare.

"Every place that we've had a positive tick, we've had a patient case," Dr. Stromdahl emphasized. "The numbers are small, but I want to give an early warning before more people get sick."

 
The Dangers of Babesiosis: Malaria-Like Symptoms

Babesiosis is caused by parasites of the genus Babesia, which, when viewed under a microscope, show blood infection patterns similar to malaria. While a quarter of infected individuals remain asymptomatic, those who develop symptoms, particularly the elderly or immunocompromised, can become severely ill with high fever, chills, anemia, fatigue, and jaundice. If left untreated, the parasites can infect and destroy red blood cells, potentially leading to organ failure and death.

Babesiosis typically occurs primarily in the Northeastern and upper Midwestern United States. From 2015 to 2022, the number of cases increased by 9% annually in states that regularly report the disease, including Connecticut, Massachusetts, Minnesota, New Jersey, New York, Rhode Island, and Wisconsin. Researchers attribute this increase to rising temperatures due to climate change, as warmer temperatures provide favorable conditions for blacklegged ticks to bite humans more often and expand their habitats.

 
Climate Change: A Major Driver of Tick Proliferation

While climatic conditions in the southern Mid-Atlantic region have always been hospitable to ticks, recent years of consistently warmer-than-average winters are turning some states in the region into year-round breeding grounds for ticks and small rodents like mice, squirrels, and voles (animals that carry the Lyme bacteria and Babesia parasites in their blood). Above-average annual rainfall moistens the soil and increases humidity throughout the region, further promoting tick reproduction. The winter season of 2023-2024 was 4 to 6 degrees Fahrenheit (approximately 2.2 to 3.3 degrees Celsius) warmer than average across most of the Mid-Atlantic, with many states also recording record rainfall in December and January.

Dr. Stromdahl has been studying tick migration and tick-borne diseases for decades. She has observed everything from the northward spread of the Lone Star tick, which can trigger a potentially life-long and sometimes deadly reaction to red meat. Yet, even she was shocked by how far the Babesia parasite has spread.

She and her co-authors collected 1,310 ticks from Virginia, Maryland, and Delaware, finding the Babesia microti parasite in all three states. This suggests the potential for more human infection cases throughout the southern Mid-Atlantic. The parasite had not been previously found in ticks in these states.

 
The Interrelationship Between Lyme Disease and Babesiosis

Many of the ticks examined by researchers were also infected with the bacteria that causes Lyme disease. The link between Lyme disease and Babesiosis is an active area of research. Experts hypothesize that ticks infected with one disease may be more susceptible to infection with the other, though the exact reasons are not yet clear. However, it is evident that Lyme disease is a precursor to Babesiosis. Previous studies on tick-borne diseases have shown that regions with increasing Lyme disease cases from the 1980s to the early 2000s reported more Babesiosis cases 1 to 20 years later.

Shannon LaDeau, a disease ecologist at the Cary Institute of Ecosystem Studies who was not involved in this study, stated, "The results from Stromdahl's paper are consistent with what we've seen in the Northeast. Babesia infections appear to be spreading where Lyme disease infections are already present."

 
Concentrated Outbreak Areas and Lack of Medical Awareness

The authors also investigated areas with concentrated human Babesiosis cases. Two areas of particular concern were the five counties surrounding and including Baltimore City and the Delmarva Peninsula (a 180-mile long coastal landmass encompassing parts of Delaware, Maryland, and Virginia). 55% of Maryland cases occurred in the Baltimore area, and about 38% of combined cases from Virginia, Maryland, West Virginia, and Washington D.C. occurred on the Delmarva Peninsula.

Experts believe that a lack of awareness among doctors leads to a significant underreporting of Babesiosis cases. Dr. Stromdahl and her colleagues hope their research findings will inspire Mid-Atlantic health authorities to recognize Babesiosis as an increasingly serious problem, conduct surveillance for infected ticks, and issue public health warnings to the public. If doctors in the region are aware of Babesiosis testing, severe cases like Duncan's could be prevented.

"The southern Mid-Atlantic region should expect cases of Babesiosis," the authors warned, adding that "tick habitat expansion is happening so rapidly that public health guidance on tick-borne disease prevention and treatment may quickly become outdated."

 
Complex Factors Driving Tick Population Growth

Climate change is not the only environmental factor driving tick population density and spread. Decades of reforestation efforts in previously denuded areas have fostered the proliferation of white-tailed deer herds. White-tailed deer act as vectors for tick dispersal, carrying ticks for miles on their bodies before dropping them into leaf litter, allowing ticks to spread. Simultaneously, a decline in recreational and subsistence hunting is exacerbating deer overpopulation. Furthermore, the expansion of suburban development into wooded areas is exposing more people to ticks and the diseases they carry.

"The most important takeaway is that tick-borne diseases are an increasing risk," emphasized Dr. LaDeau. As tick populations grow, the critical question, she added, is to identify where and when infected ticks come into contact with humans. "There's still a desperate need for data to understand how frequently these infected ticks are coming into contact with humans," she concluded.