There is no convincing evidence that classic Lyme disease occurs in Australia, nor is there evidence that the causative agent, Borrelia burgdorferi, is found in Australian animals or ticks.
These findings are the result of a study recently published as a ‘narrative review’ by the Medical Journal of Australia.
Lead author Professor Peter Collignon said there was no doubt that people were developing illnesses after tick bites.
“But the honest answer is, we don’t know why,” he said. “We have looked for B.burgdorferi and we haven’t been able to find it in any reproducible way.”
Nonetheless, despite the lack of evidence that Lyme disease can be acquired in Australia, growing numbers of patients, their supporters, and some politicians demand diagnoses and treatment according to the protocols of the “chronic Lyme disease” school of thought.
Lyme disease can be acquired overseas but diagnosed in Australia, with most people who present with laboratory-confirmed Lyme disease in Australia having been infected in Europe.
The authors of the narrative – Collignon (infectious disease physician and microbiologist at Canberra Hospital and eecutive director at ACT Pathology), Gary D Lum (also Canberra Hospital and the Australian Government Health Department), and Jennifer MB Robson (Sullivan Nicolaides Pathology, Brisbane) – warn that antibiotic therapy for chronic “Lyme disease-like illness” can cause harm to both the individual (eg cannula-related intravenous sepsis) and the broader community (increased antimicrobial resistance rates).
“Intravascular therapy kills people,” Coolignon said. “People may get complications, such as clots or other infections, such as golden staph infections or Candida infections. We know that if you get those in your blood you have a 15–20% chance of dying.
“Until there is strong evidence from well-performed clinical studies that bacteria present in Australia cause a chronic debilitating illness that responds to extended antibiotic therapy, treating patients with ‘Lyme disease-like illness’ with prolonged intravenous or oral antibiotic therapy is both unjustifiable and unethical.”
Some people believe they have acquired Lyme disease in Australia because the results of screening antibody tests to B. burgdorferi are positive, the authors say.
“However, instances in which there was no overseas exposure are all likely to be false positive test results.”
All diagnostic tests produce both false positive and false negative results; their frequency depends on the specificity and sensitivity of the test and the prevalence of the disease in the population tested.
“Even a highly specific test will produce some false positives, so that people who have never been exposed to B. burgdorferi can have reactive antibody results.”
A large private diagnostic laboratory that conducts about 250 serological tests for Lyme disease each month provided the samples discussed in the narrative. Referrals came from all Australian states, with women aged 30–50 years the largest group tested
Over a 23-month period (September 2014 – July 2016), 5372 of 5628 tests (95.5%) in 5395 patients returned negative results. Two-tier testing, including an immunoassay followed by an immunoblot, was performed on the 256 samples (4.5%) for which the screening results were equivocal or positive; the western blot results for three-quarters of these samples (177 of 256) were negative, and the screening results were classified as false positive results.
Seventy-nine samples (1% of all samples) returned positive results for both the screen immunoassay and an initial immunoblot. Results for a large subset of these patients (29 of 79, or a further 0.5% of all tests) with a low pre-test probability of infection (no relevant symptoms or epidemiological risk factors) were negative on a second immunoblot.
The total number of true positive tests was therefore 50 (0.9% of all tests), from a total of 43 patients. The total number of false positive results was 206 of 256 positive screening tests, or 80.5%.
“These results highlight the fact that commercially available systems use different recombinant antigens and apply different criteria for a positive result,” the review report says. “Because of these variations, this second tier of testing should be regarded as an additional test, with a greater emphasis on specificity, supporting the clinical diagnosis rather than confirming it.
“While immediate treatment solutions for patients presenting with these symptoms are not readily available, we strongly recommend a multidisciplinary approach to the investigation, diagnosis and management of ‘chronic Lyme disease’. This is especially important for ensuring that alternative diagnoses are not missed or ignored. Engaging with general practitioners, specialist physicians and microbiologists is critical for helping each patient.”