Tick-Borne Terror of Babesiosis
By Penn State University
Rates of babesiosis, a tick-borne parasitic disease, increased by an average of 9% annually in the United States from 2015 to 2022, with four in 10 patients also infected with another tick-borne illness such as Lyme disease. This is according to a new study from Penn State Health Milton S. Hershey Medical Center and Penn State College of Medicine.
“These findings suggest that clinicians should have a
heightened vigilance of co-infection of other tick-borne illness among patients
admitted with babesiosis,” said Paddy Ssentongo, infectious disease fellow,
Penn State Health Milton S. Hershey Medical Center and lead author of the
study. “Ticks can carry other bacteria that cause Lyme disease and other
tick-borne diseases like anaplasmosis and ehrlichiosis.”
They published their findings on October 8 in the journal Open Forum Infectious Diseases.
Understanding Babesiosis and Its Transmission
Babesiosis, sometimes referred to as “American malaria,” is
caused by the Babesia parasite and is transmitted from bites
of black-legged ticks. It’s found primarily in Northeastern and Midwestern
states. Like malaria, the parasite infects red blood cells, and the condition
shares many similar clinical symptoms. According to the U.S. Centers for
Disease Control and Prevention (CDC), although some people do not develop
symptoms, others experience flu-like symptoms. The disease can be deadly for
older adults and those with certain health conditions, such as a weakened
immune system or lack of spleen.
“Understanding the drivers, dynamics, and control of endemic
and emerging vector-borne diseases is critical for global health
interventions,” Ssentongo said.
The prevalence of babesiosis has been rising, according to the CDC. Ssentongo explained
that climate change may play a role. Changing factors like temperature,
humidity, rainfall, and length of season have influenced the population and
distribution of vectors like ticks as well as the population of animals that
serve as reservoir hosts, like deer. As a result, ticks may be present in a
wider geographical area.
Investigating Prevalence and Mortality Risks
The team set out to assess the current prevalence of
babesiosis and Babesia co-infections as well as the effect
of Babesia co-infection on mortality risk. Using the TriNetX,
a large, national database of clinical patient data from over 250 million
individuals, they identified 3,521 individuals who were infected with
babesiosis between October 2015 and December 2022.
The researchers found that the incidence of babesiosis
increased an average of 9% per year. The majority of cases peaked during the
summer months and were reported in Northeastern states. Of those diagnosed with
babesiosis, 42% were infected with one or more additional tick-borne disease,
which is a higher rate than what’s been found in previous studies. The greatest
percentage of those patients, 41%, were co-infected with the bacterium
responsible for Lyme disease while a smaller portion of patients were co-infected
with bacteria that cause ehrlichiosis and anaplasmosis, 3.7% and 0.3%,
respectively.
When the team examined if co-infection amplified the risk of
complications or led to worse outcomes, they found that there were no
significant differences between the babesiosis-only group and the co-infection
group. However, when they looked at mortality risk, they found that the risk of
death was higher among the babesiosis-only group.
Treatment Strategies and Prevention
“Having both babesiosis and Lyme disease seemed not to be
associated with worse mortality,” Ssentongo said, noting the finding was
surprising. “It’s speculated that the concurrent presence of other tick-borne
infections in the blood could alter the immune response by possibly ‘boosting’
it to effectively fight infections.”
The difference in outcomes may also have to do with how
other tick-borne illnesses are treated, Ssentongo said. In their study, the
team found that the co-infection group was more likely to be prescribed
doxycycline, the first line antibiotic treatment for Lyme disease,
anaplasmosis, and ehrlichiosis, compared to the babesiosis-only group.
Ssentongo said that it raises a compelling question: Is doxycycline also
effective in treating the babesia parasite?
Currently, the treatment of babesiosis depends on disease
severity. Treatment typically includes a combination of the antibiotics
azithromycin and atovaquone. Red blood cell exchange, where abnormal red blood
cells are removed and replaced by healthy ones, can also be considered for
severely ill patients such as those with serious organ dysfunction. However,
the survival benefit of red blood cell exchange hasn’t been studied
extensively.
“For patients with babesiosis, we add on doxycycline as
we’re investigating whether or not the patient has Lyme disease or other
tick-borne diseases, and we’ve seen better outcomes at our medical center with
this approach,” Ssentongo said. He said that there are other case reports where
babesiosis has been successfully treated with doxycycline. However, more
research is needed to understand the physiological pathways that underlie
co-infection and how that might influence treatment protocols.
The most effective treatment approach is preventing
tickborne diseases in the first place, according to Ssentongo.
“If you live in areas where babesiosis is endemic, mostly
states in the Northeast and the Midwest, take precautions, especially during
the summer months,” Ssentongo said. “Practice tick-bite prevention practices.
Wear long-sleeved shirts and pants and light-colored clothes. Use tick
repellant and check for ticks after spending time outdoors.”
Reference: “Beyond Human Babesiosis: Prevalence and
Association of Babesia Coinfection and Mortality in the United States,
2015-2022: a Retrospective Cohort Study” 8 October 2024, Open Forum
Infectious Diseases.
DOI: 10.1093/ofid/ofae504