In a new case study, researchers from North Carolina State University found Bartonella henselae, Babesia odocoilei and Babesia divergens-like MO-1 DNA in brain tissue samples from a young child with seizures and suspected Rasmussen's encephalitis. The findings further support the idea that these pathogens can be a cofactor in complex neurological illnesses.
Bartonella are a group of vector-borne bacteria transmitted primarily via arthropods like fleas, lice and potentially ticks, but also by the animals that harbor them. Of the (at least) 45 currently known Bartonella species, 18 have been found to infect humans. The most commonly known species is Bartonella henselae, which causes cat scratch disease in humans.
Improved methods for detecting Bartonella infection in animals and humans have led to the diagnosis of bartonelloses in patients with a host of chronic illnesses, as well as in some patients with psychiatric symptoms.
Babesia is a malaria-like protozoa that infects red blood cells. In the U.S., the main Babesia species that infect humans are B. microti, B. duncani and B. divergens-like. Transmission occurs mainly by tick bite, but there are reports of transmission by transfusion of contaminated blood, organ transplantation and transplacental transmission.
Babesia and Bartonella are often suspected as co-infections with Lyme disease, caused by the bacterium Borrelia burgdorferi.
The child in the case study had suffered facial scratches from a feral cat at the age of two, then developed seizures two years later after suffering an insect bite and subsequent rash. In 2022, six years after the facial cat scratch, the NC State team was asked to test blood samples - and subsequently, brain biopsy samples - from the patient.
In January 2022, the NC State team attempted to amplify Bartonella and Borrelia DNA from patient blood samples via qPCR and digital droplet PCR testing, but results were negative.
In June 2022, the team tested samples from the patient's brain biopsy for Bartonella, as well as for Babesia, due to the insect bite and rash. They also tested blood samples for Babesia. Using molecular methods, they were able to detect DNA of Bartonella henselae and two species of Babesia - B. odocoilei and B. divergens-like MO-1- in the brain tissue samples. The two Babesia species were also present in the patient's previously submitted blood samples.
"The interesting lesson we learned from this particular case was that Bartonella DNA was not detected in the initially tested blood samples, despite detection of the organisms' DNA in the brain tissue culture samples," says Edward Breitschwerdt, Melanie S. Steele Distinguished Professor of Internal Medicine at NC State's College of Veterinary Medicine and corresponding author of the paper.
"The brain is usually considered an 'immune privileged site,' meaning that it is difficult for an infection to cross that barrier," Breitschwerdt says. "But given that pathophysiological changes were observed on the same side of the patient's brain where the facial scratches were received, and that neurological issues are sometimes associated with chronic Bartonella infection, this case emphasizes the potential for chronic bloodborne or central nervous system infection following a cat scratch.
"The other unexpected piece to this puzzle is the potential effect of the Babesia infection," Breitschwerdt adds. "Unfortunately, there is minimal information on acute babesiosis with these two novel human pathogens and neurological disease and essentially none on the role of chronic Babesia infection and neurological symptoms. So, we need to ask ourselves going forward what we may be missing in cases like this child."
The work appears in the Journal of Central Nervous System Disease and was supported by the Steven & Alexandra Cohen Foundation. NC State researchers Ricardo Maggi and Emily Kingston also contributed to the work.
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