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Lyme-like disease may result from related unknown bacteria

Lyme disease is caused by the bacterium Borrelia burgdorferi, which is carried by ticks. Mike K/Flickr, CC BY-NC-SA

A government investigation into whether Lyme disease exists in Australia and how to treat it has ended without being able to resolve the issues. But there is a plausible explanation for why people here report a Lyme-like disease.

Instituted by the chief medical officer, the Clinical Advisory Committee on Lyme Disease was set up in 2013 to work out how to diagnose and treat what it called “Lyme disease-like syndrome”. But the committee says that can’t be done until we know what causes the illness and how it is spread.

Named after the town of Lyme in Connecticut where it was first identified in the 1970s, Lyme disease is caused by the bacterium Borrelia burgdorferi, which is carried by ticks. It causes flu-like symptoms with associated fatigue, muscle pain and various neurological symptoms. It also causes a bulls-eye rash to develop around the site of the tick bite.

The bacteria has not been identified in any tick in Australia, but many people have nonetheless been diagnosed with Lyme disease or Lyme-like illness, based on their symptoms. The diagnosis is often complemented with laboratory tests from Australian and overseas laboratories.

The controversy about the disease arose because the official position is that Borrelia burgdorferii doesn’t exist in Australia, and that positive lab tests are from people acquiring infection outside the country or the tests are false positives. The net result was that doctors were unwilling to give the diagnosis, often despite positive lab results, and prescribe the necessary antibiotic treatment.

Testing infection

The DNA sequence of Borrelia burgdorferi. AJ Cann/Flickr, CC BY-NC-SA

There are a number of ways to test the cause of a bacterial infection. The first to identify the causative agent, isolate it and grow it in pure culture. If you can induce the disease by injecting or ingesting that pure culture and if you can re-isolate it from the new host, then that bug is the cause of the disease. This is the best form of proof.

The next best way is to undertake DNA sequencing to assign the bug to a particular species, family, and genus. But this sort of testing has proven contentious in the case of Lyme disease for both patient blood samples and bacteria from Australian ticks.

We know Australia’s common bush or grass ticks Ixodes holocyclus carry a strain of Borrelia, but a DNA probe study another research group failed to find the organism in Australian ticks.

One reason for this anomaly could be the genes used as targets of the DNA probe. If that gene is shared by all Borrelia bacteria, then the bug will most likely be detected. But if the probe detects a gene specific to Borrelia burgdorferi from the Lyme region of Connecticut, it’s likely that related organisms, such as Borrelia cousins, may not be detected.

The third option is to study the antibodies in the blood of infected people. The problem with this approach for identifying Lyme disease in Australia has revolved around the validity of the tests done here and abroad. The criteria used to detect positivity are not agreed on and questions have been raised about whether the testing laboratories are appropriately accredited.

But that doesn’t resolve the dilemma facing people who arrive at their doctor’s rooms with a positive test in hand from a lab in Germany or the United States or Australia and are told the tests cannot be believed.

An alternative explanation

The problem at the heart of the issue is that Borrelia burgforferii causes a unique set of symptoms, but tests for this organism are often negative in people with Lyme-like symptoms.

Lyme disease causes a bulls-eye rash to develop around the site of the tick bite. Chris Booth/Flickr, CC BY-SA

So, does the problem lie with the test, or is the patient actually not infected? Could they have another infection with similar symptoms? There’s no way to know the answer unless we test for each specific bacterium.

But there’s a recent US report of patients infected with a new strain of Borrelia – Borrelia miyamotoi. This organism was found in ticks many decades ago but, until recently, it wasn’t known to infect humans.

The first report about this bacteria was from Russia where genetic analysis using DNA probes found the organism associated with a relapsing fever in 46 people. Spinal fluid analysis showed a Borrelia-like wiggling spiral-shaped bacterium but DNA tests failed to find the classic Lyme disease organism Borrelia burgdorferi, only the previously innocuous Borrelia miyamotoi.

A new infective diagnosis became both possible and plausible for people with Lyme-like symptoms. Could Australia not have a unique strain of Borrelia that only shares some of its identity with the tested for Borrelia burgdorferi?

I suspect there does exist in Australian animals at least two tick-transmitted Borrelia organisms that cause Lyme-like disease.

People with Lyme disease’s traditional bull’s eye rash could well be carrying the American Borrelia burgdorferi. But those without the rash who test negative to Borrelia burgdorferi may be carrying an Australia-specific Borrelia.

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