Tick-bite illnesses can be complex and debilitating. Are we any closer to understanding them?

Over three decades as a GP in northern Sydney, Richard Schloeffel saw thousands of patients with complex chronic diseases.

Many lived with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), while others struggled with long COVID.

But it was a group of patients with debilitating, ongoing symptoms linked to tick bites that prompted the now-retired GP to undertake further research.

"I think tick-borne illness can be treated," Dr Schloeffel, now a researcher at Macquarie University, said. 

Once described as "Lyme-like illness", thousands of Australians have reported suffering persistent symptoms, including fatigue, joint pain and neurological problems, they believe to be the result of a tick bite.

In 2018, the federal Department of Health coined the term DSCATT — debilitating symptom complexes attributed to ticks — to recognise these patients, and established clinical recommendations to help doctors manage them. 

But the cause of their symptoms, and how best to treat them, remains highly contested in the medical and scientific community.

Earlier this year, a Senate inquiry found many patients struggled to access care and sometimes spent thousands of dollars, including on unproven testing and treatment, to find answers.

"Most people in Australia who get a tick bite don't get sick. We're talking about the tip of the iceberg," Dr Schloeffel, who has long advocated for patients with tick-bite associated illnesses, said.

But for those who do report illness, many struggle to feel believed or seen.

"People bankrupt themselves to find treatment and get diagnosed," Dr Schloeffel said.

Following an earlier Senate inquiry in 2016, the federal government awarded funding to Australian researchers to investigate the causes of DSCATT and potential treatments.

Scientists have been slowly making inroads, but many questions remain unanswered.

Tick-borne diseases in Australia

There are around 70 species of ticks in Australia, 17 of which bite humans, Peter Irwin, a veterinary scientist and tick researcher at Murdoch University, said.

While usually harmless, tick bites can cause a range of illnesses, including allergic reactions, bacterial infections and, less commonly, paralysis.

"On the east coast of Australia, the main tick is the Australian paralysis tick (Ixodes holocyclus)," Professor Irwin said.

"The other main tick of medical importance is the kangaroo tick (Amblyomma triguttatum), which lives almost all over Australia."

Allergies are the most common adverse reaction to tick bites, and range from mild (lasting a few days) to severe (including life-threatening anaphylaxis).

In some cases, people develop mammalian meat allergy (also known as alpha-gal syndrome) after a tick bite, which results in them no longer being able to eat red meat and other products derived from mammals.

Ticks can also carry Rickettsia bacteria, which cause infections including Queensland tick typhus, Flinders Island spotted fever, and Australian spotted fever.

These infections are most commonly seen in people who live in high-risk areas such as northern Sydney, and are usually treated with a short course of antibiotics.

Is Lyme disease in Australia?

In recent years, a growing number of Australians have reported suffering debilitating, ongoing symptoms they believe to be the consequence of a tick bite — but their illnesses cannot be easily diagnosed or treated.

In some cases, people believe they have contracted Lyme disease, a tick-borne infection commonly found in parts of the US, Europe and Asia, which can sometimes lead to persistent symptoms like severe fatigue, muscle pain and cognitive problems.

But according to Professor Irwin, there is no evidence that the infection can be acquired in Australia as no Australian ticks have been found to carry Borrelia burdorferi, the bacterium responsible for Lyme disease.

"There's nothing difficult about finding Borrelia bacteria overseas, and of course, there is Lyme disease overseas," Professor Irwin said.

"But in Australia … no-one has ever been able to find Borrelia burgorferi."

Other Borrelia species have been identified in Australia, but it is not known whether they can be transmitted to humans by ticks.

Without local evidence of Borrelia burgdorferi, the diagnosis of locally acquired Lyme disease is not supported by Australian health authorities.

Adding to the challenge is the fact DSCATT symptoms can overlap with other infectious and chronic diseases, and not everyone affected has a clear history of a tick bite.

Symptoms of patients with lingering health issues who do not meet the criteria for a recognised disease or infection are usually deemed "medically unexplained" — and treatment options are limited.

"What DSCATT guidelines do is … basically stop any further investigation or treatment being available," Dr Schloeffel said.

One of the recommendations of this year's Senate inquiry was to replace the current DSCATT clinical pathway with new guidelines.

"That patients continue to experience debilitating and severe symptoms and that patients are left without a diagnosis or treatment plan is of serious concern," the final report noted.

Searching for an answer

To understand what might be causing some people to experience ongoing, "medically unexplained" symptoms, Professor Irwin and his colleagues at Murdoch University received funding in 2019 to closely track Australians after they received a tick bite.

"The idea was to perhaps find which of the Australian microorganisms could be the equivalent of Lyme Borrelia bacteria overseas," Professor Irwin said.

The research team followed 118 people over 12 months, taking blood samples and skin biopsies, and studying the ticks responsible for the bites.

"We sampled people within 72 hours of a tick bite … and then again at one week, three months, and 12 months, with the idea we would monitor them for all sorts of things to try to detect patterns, biological processes, infections and so on."

The results of the study, which was delayed by COVID, are due to be peer-reviewed and published in the coming months. But preliminary findings suggest a small number of participants experienced symptoms "similar to those reported by DSCATT patients" at 12 months, Professor Irwin said.

"[They had] migraines, headaches, dizziness — the sorts of signs that have been attributed to ticks."

In addition to looking for new pathogens, Professor Irwin said the research team was investigating whether known bacteria, viruses and parasites could be causing long-term illness.

"Some of our patients developed evidence of rickettsial infection, as you'd expect, and we're looking very hard to see whether any of those patients went on to develop DSCATT symptoms," he said.

"The question is: could [an infection] have caused an acute localised or even systematic reaction, and has that triggered — in some people — the propensity to develop DSCATT symptoms?

"That's what we're trying to unravel."

Diagnosing and treating an invisible illness

The question of if — and how — tick-borne diseases cause chronic infection, inflammation or other ongoing biological changes is something scientists overseas are also investigating.

The current uncertainty, and lack of scientific evidence, is why "chronic Lyme disease" is a disputed and controversial diagnosis. Instead, health authorities, including the US Centers for Disease Control (CDC), use the term "post-treatment Lyme disease syndrome" to describe people who experience prolonged symptoms.

"Chronic Lyme disease … implies that prolonged symptoms are caused by an ongoing bacterial infection when, in fact, the cause is not currently known," the agency noted.

In Australia, patients with unexplained chronic symptoms linked to tick bites generally do not show any evidence of infection or irregularities in standard blood tests, Dr Schloeffel said.

"There's this general belief that if you can't measure something, they look alright and they've tested normal, there is nothing wrong with them."

The former GP believes the lack of pathological evidence is a reflection of inadequate diagnostic testing, not the absence of disease, and is something he is working on trying to improve.

According to Dr Schloeffel, possible mechanisms driving the persistence of symptoms — which would be missed in standard blood tests — include infection-induced immune dysfunction and chronic inflammation inside cells.

Through a privately funded clinical trial at Royal North Shore Hospital in Sydney, Dr Schloeffel and his colleagues are monitoring a range of biomarkers in 60 DCSATT patients in the hope of establishing new diagnostic markers and tests.

Separately, Dr Schloeffel also plans to evaluate whether treatments some DCSATT patients have been prescribed have any benefit, including medications to aid with sleep and inflammation, as well as low-dose, long-term antibiotics — a treatment that is not recommended by health authorities in Australia, and described as having "known harm and no benefit" in current treatment guidelines.

In its submission to the 2024 Senate inquiry, the Royal Australian College of General Practitioners (RACGP) noted that "negotiating diagnostic uncertainty" could be challenging and frustrating for patients, but there was "little or no evidence to support specific treatments for tick-borne diseases".

"We need to be mindful that unnecessary medications, testing or procedures are low-value care and can cause more harm than benefit."

Focus on improving quality of life

In 2019, alongside funding the Murdoch University study, the government also awarded University of Melbourne researchers a grant to investigate whether a psychology-based intervention could help people with DSCATT manage their illness.

Richard Kanaan, a professor of psychiatry and research leader, said the nine-month therapy — designed to be given in addition to other treatments or supportive care — was developed with a goal to improve patients' quality of life.

The intervention was adapted from existing approaches used to help treat other chronic and complex illnesses where the cause was unclear.

"The treatment is one that has been tried successfully with a number of similar diseases … where people get an infection, think of the infection itself as being short-lasting, but the after-effects can go on for a long time and be very debilitating," Professor Kanaan said.

"We're not necessarily talking about a cure, because people … may go on having the illness. But we're talking about improvement."

In coming months, the researchers will assess the feasibility of the intervention they have developed — which is based on acceptance and commitment therapy — and evaluate whether it has any therapeutic effects.

Professor Kanaan said the research team had received some criticism from people with DSCATT concerned about the psychological nature of the treatment — and implication their illness was being viewed as a "disease of the mind", not the body.

"I absolutely do not believe that."

The term DSCATT itself has been widely criticised by patients, in part because it defines symptoms as being "attributed" to — rather than caused by — ticks. This year's Senate inquiry also recommended the term be replaced.

Professor Kanaan said investigating the benefits of psychological therapy in no way reduced the seriousness of the illness.

"Why psychiatry is involved is because understanding a complex problem — it needs a holistic approach," Professor Kanaan said.

"As much as we'd like there to be a very simple explanation … it doesn't seem to be that kind of problem."

Editor’s note 10/11/25: This story was updated to clarify that Dr Schloeffel intends to evaluate the effects of various treatments some DSCATT patients have been prescribed, but that this is not part of the trial currently being undertaken at Royal North Shore Hospital.