This is the first time anyone has studied how many people in Norway associate chronic health problems with tick bites, says researcher Audun Olav Dahlberg.
He is a senior consultant at the Hospital in Nordmøre and Romsdal.
"The symptoms are real, and many experience a significant loss of function. At the same time, we must clearly communicate what the research shows," says Dahlberg.
"It's a challenging balance: we need to inform that tick-borne diseases can be serious, while also explaining that long-term symptoms, after thorough evaluation, are usually not caused by a persistent infection," says Audun Olav Dahlberg.(Photo: Private)
In his doctoral work at NTNU, he studied 470 Norwegian women and men. All believed that their long-term chronic symptoms started after a tick bite. They had experienced symptoms for more than six months.
"After thorough investigation, we generally do not find evidence of chronic tick-borne infection," he says.
Annonse
Several had received a diagnosis
Several reported that a doctor had given them a diagnosis related to tick bites.
"It's important to distinguish between self-reported diagnoses and those documented in medical records," says Dahlberg.
Only a small portion of those who provided medical records had confirmed that they had a tick-borne disease before their symptoms began.
But the researchers found no signs of any current infection that could explain the symptoms.
How were the participants tested?
The researchers used both antibody tests and molecular blood tests to determine whether participants had an infection.
If there was still an active infection, there would usually be a clear antibody response in the blood, since the participants said they had experienced symptoms for over six months, explains Dahlberg.
"When we find no connection between physical symptoms and antibody response, along with minimal findings from molecular tests, it suggests that there is no ongoing infection," he says.
In other words, no link was found between test results and the severity of symptoms.
"The tests we used do not measure all aspects of the immune system. Therefore, we cannot completely rule out the possibility of immune-related mechanisms we are not detecting. This has not yet been fully clarified," he says.
No clear evidence that many in the population suffer from tick-related illness
It is possible to become seriously ill from tick bites, according to the researcher.
"But at the population level, the study does not indicate that a large number of people have long-term symptoms due to a tick-borne infection," he says.
Even so, Dahlberg stresses that these patients must be met with respect.
"Not finding signs of an active infection does not mean the symptoms aren’t real. Long-term health problems often have multiple causes," he says.
He believes doctors need to make thorough evaluations. They need to both rule out other diseases and explain what the tests can and cannot show.
The patients had some things in common
Researchers found that the group with long-term symptoms had several things in common.
They were less physically active. Fewer were employed, and more had additional health issues.
Annonse
They also reported a higher number of symptoms compared to the control group.
"They described fatigue, various physical complaints, and poorer physical health. They also reported more anxiety and depression, as well as greater concern about their own health," says Dahlberg.
Many had previously had the bacteria
To recruit participants, the researchers sent SMS messages to 270,000 randomly selected people across Norway. General practitioners, the National Competence Centre for Tick-Borne Diseases, and the Norwegian Lyme Borreliosis Association also contributed to recruitment.
About 60 per cent of the 470 participants who ultimately took part in the study had documented and treated borreliosis.
More than one in three had antibodies against the bacteria that usually causes borreliosis. This means that many had been infected and developed an immune response.
The research project was a collaboration between Møre og Romsdal Hospital Trust, the Tick Centre at Sørlandet Hospital, and the Norwegian Institute of Public Health.
More common in areas with more ticks
The researchers included participants from areas with many ticks and areas with fewer ticks.
There was also a control group from Søgne, an area known for many ticks. This group did not report persistent symptoms.
Long-term symptoms were more common in areas with more ticks and borreliosis. According to Dahlberg, this may indicate that local awareness of the disease influences how people interpret their symptoms.
"Lyme disease has long been called 'the great imitator' because it can produce a wide range of symptoms. This has likely contributed to increased public attention," he says.
When a single illness can account for many different symptoms, it becomes easier for people to use it as an explanation for health issues that are otherwise hard to make sense of.
Dahlberg points out that symptoms often associated with chronic tick infection – such as fatigue, pain, and concentration difficulties – are also common in the general population.
If these symptoms appear after a tick bite, it's natural to link them together. But that does not necessarily mean that the tick is the cause, the researcher says.
"For many, it can feel easier to believe the symptoms are due to an infection. That provides a concrete explanation and a clear 'enemy.' When there are no clear answers, it can be difficult to accept more complex explanations," says Dahlberg.
"It's a challenging balance: We need to inform that tick-borne diseases can be serious and require treatment, while also explaining that long-term symptoms after thorough evaluation are usually not caused by a persistent infection," he adds.
"Some limitations"
Linn Kristin Aalmo, chair of the Norwegian Lyme Disease Association (NLBF), writes to Science Norway on behalf of the board that the study has some limitations, which are also acknowledged in the article. For example, a considerable number of participants did not want to give researchers access to their medical records.
"From what we can see, PCR testing has been used extensively. At present, there are no tests that can provide a 100 per cent accurate result," Aalmo writes.
She also notes that several doctors believe a portion of their patients have immune systems that do not function optimally, which could affect symptoms, test outcomes, and disease progression.
Researcher: This is the gold standard
Randi Eikeland, head of the National Centre for Tick-Borne Diseases, writes in an email to Science Norway that it is correct that only 36 per cent allowed Dahlberg to review their medical records.
Randi Eikeland believes that one of the most important takeaways from the study is how crucial it is to try to identify the causes of long-lasting, unexplained health problems.(Photo: University of Agder)
However, she believes that the number of affected individuals, their questionnaire responses, and their blood test results do not depend on whether researchers had access to their medical records.
"It's also incorrect to say that only PCR tests were used. The main method was antibody testing in blood, which is considered the diagnostic gold standard for most of these conditions," she writes.
"We have learned from many infecious diseases that the immune system plays a key role in whether people continue to experience symptoms after an infection, rather than whether the pathogen itself remains in the body after antibiotic treatment," she writes.
"Especially after the Covid-19 pandemic, where many people take a long time to fully recover," she adds.
There is still a great need for more research to better understand how and why this happens, according to Eikeland.
She notes that she has been involved as a researcher in the overall project and co-authored two of Dahlberg’s articles, although she did not take part in this particular article.
A larger study has been conducted before
The patient association NLBF notes that a much larger study on long-term health problems after tick bites has been carried out before.
A study followed 1,100 patients with Lyme disease over the course of a year.
"It found that 27 per cent of participants experienced persistent symptoms such as fatigue, pain, and cognitive difficulties," they write.
Eikeland believes it is wrong to dismiss the possibility that some individuals develop long-term, and sometimes very serious, complications after infection with tick-borne pathogens.
"This is well documented in multiple studies from recent years," says the researcher.
Eikeland considers one of the key takeaways from the study to be the importance of identifying the causes behind these persistent and unresolved health problems, which affect many people.
"Based on our own experience and research from other countries, we have long suspected that borreliosis may be overdiagnosed in this group and that the symptoms are not due to ongoing infections from tick-borne pathogens," she writes. "We are very pleased that these results have now been published. It's always interesting to discuss how certain one can be about the results."
The Association of General Practitioners: Current treatment options are inadequate
"Patients need to feel that they are taken seriously, even when there are different opinions about the underlying cause," says Torgeir Hoff Skavøy, head of the Norwegian Association of General Practitioners.
Torgeir Hoff Skavøy, head of the Norwegian Association of General Practitioners, believes doctors also need to consider mental health, sleep, and the patient's work situation.(Photo: Thomas B. Eckhoff)
Doctors must determine whether patients have other illnesses. They should also assess mental health, sleep, and the patient's work situation, he believes.
Skavøy also believes many patients would benefit from multiple professionals collaborating.
"At present, we do not offer adequate treatment options for patients with these long-term health problems," he says.
