Postmortem Study Finds Babesia and Bartonella DNA in Five of Six Young People

He had once been fit and well. Years later, he was living with fatigue, pain, memory difficulties and psychiatric symptoms. In the end, he was forced to leave university.

When the 27-year-old died, six years of illness and specialist treatment had not returned him to good health.

Testing conducted after his death detected DNA from two species of Babesia - tiny parasites that infect red blood cells - as well as Bartonella henselae, the bacterium responsible for cat-scratch disease.

His case was among six examined in a postmortem investigation initiated by families searching for explanations for their children's illnesses.

Researchers verified DNA from either, or both, groups of microbes in five of the individuals. However, the findings left a central issue unresolved: whether the infections had played any part in their illnesses.

Babesia and Bartonella DNA in postmortem samples

The individuals were between 14 and 30 years old, and each had lived with chronic illness alongside suicidal thoughts or behaviours.

Four died by suicide, one died through medical assistance in dying, and one died from a serious condition marked by excessive immune activation.

Their parents approached Edward Breitschwerdt, an infectious-disease researcher at North Carolina State University, after hearing about his team's research into Bartonella and neurological illness. They provided medical records and arranged for postmortem specimens to be sent to his laboratory.

Several of the individuals had already undergone testing or received treatment for these infections during their lives. Therefore, this investigation did not provide the first sign of infection in every case.

The laboratory's first analyses did not produce definitive results. Researchers examined 125 DNA extracts taken from blood, laboratory blood cultures, tissue and other bodily fluids. Initial quantitative PCR screening - a method that looks for chosen genetic sequences - was negative in every sample.

Digital PCR, which separates samples into numerous tiny reactions, subsequently generated weak signals in certain samples. Yet none met the study's cut-off for a positive result.

Further targeted testing and DNA sequencing, which reads genetic material to identify organisms, then confirmed the findings. Babesia DNA was found in four people, two of whom had more than one species. B. henselae DNA was confirmed in two people. One individual had both, making five in total.

Controls used by the laboratory to monitor contamination all remained negative. A faint signal for Borrelia - a bacterial group that includes the pathogens causing Lyme disease - could not be verified through sequencing.

What the infection findings can and cannot show

These microbes enter the body by different routes. Babesia may be transmitted through tick bites, which can also spread other disease-causing microbes.

B. henselae can be passed on through scratches from cats carrying infected fleas. The US Centers for Disease Control and Prevention states that there is no evidence ticks transmit Bartonella to people.

The subsequent question was whether the DNA indicated an infection that was still active at death.

When asked whether the findings could distinguish active infection from residual DNA, Breitschwerdt recognised that the issue is scientifically debated. However, he said that detecting DNA from a known pathogen in clinical samples is medically accepted as evidence of "active infection".

Clinical interpretation nevertheless depends on context. Guidelines from the Infectious Diseases Society of America state that PCR results for Babesia microti, one of the parasite species detected, may stay positive for months or more than a year after standard treatment, including after symptoms have disappeared.

Persistent DNA does not usually mean treatment has failed.

Nor does identifying these infections prove that they caused the young people's psychiatric symptoms or deaths.

Possible links between infection and neurological symptoms

How might an infection influence the mind?

A review referenced by the researchers outlines two potential mechanisms: microbes may act directly on the nervous system, or the body's immune response may alter brain function.

The team considers inflammation a possible connection between infection and some of the young people's symptoms, but the postmortem evidence cannot demonstrate that this sequence of events occurred.

"This was an observational study, not a prospective case-controlled study," Breitschwerdt told ScienceAlert.

"I think the best interpretation is that infections with vector-borne pathogens that have evolved to induce persistent infections in animals and human patients are not a current diagnostic consideration in patients with chronic illnesses or neuropsychiatric symptoms."

The families had actively sought testing, and the study had no comparison group. As a result, the findings cannot establish whether these infections occur more frequently among people experiencing suicidal symptoms.

Sample types and collection times differed, with some obtained days after death. All six individuals had been given antimicrobial medication, which may have reduced the chances of detection. The movement of bacteria after death may also have influenced the blood-culture results.

Breitschwerdt says robust evidence and research funding will be required to establish whether persistent infections causally contribute to suicidality. He advocates for a national centre to investigate chronic infections in people whose illnesses remain unexplained.

"We need an initiative similar to the start of the National Cancer Institute," he says.

The paper states that Breitschwerdt and Ricardo Maggi cofounded Galaxy Diagnostics, which offers Bartonella testing, and that both hold leadership positions at the company. Coauthor Henry Lindner is related to one of the individuals in the study.

For the families, the work has revealed molecular evidence they can continue to investigate. Whether those infections help account for what happened to their children is still unknown.

The research appears in Parasites & Vectors.

If this story has raised concerns or you need to talk to someone, please consult this list to find a 24/7 crisis hotline in your country, and reach out for help.

This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. Although we take pride in our process, we are only human. If you notice an error, please tell us.