New research: Infrared thermography makes the bullseye rash more visible for diagnosis of Lyme

Lyme disease can be a hard condition to diagnose at the best of times, but it can be particularly difficult when patients don’t display some of the most common early symptoms. 

One of those signs is the erythema migrans rash that physicians look for when someone comes to them with a tick bite. But what if that telltale visual signal isn’t there? Some doctors dismiss Lyme disease as a diagnosis if they can’t see it, and often lose valuable time waiting for blood test results that are slow to come back –  or that might be inaccurate – before prescribing antibiotics.

The lack of a visible rash is common.¹ A group of researchers at the Ternopil National Medical University in Ukraine  decided to see if thermal imaging could detect the bullseye configuration surrounding the tick bite – even if the inflammation isn’t visible to the naked eye. The five scientists published their findings in the September edition of Dove Press, an open-access online publisher of peer-reviewed scientific and medical journal articles.

“In this study, we used a special imaging method called infrared thermography, which detects subtle changes in skin temperature, to examine the site of a tick bite in people who did not have a visible rash,” the authors wrote in the article titled “Thermographic Assessment of Lyme Borreliosis Without Erythema Migrans.”

Their research is particularly pertinent not only to public health professionals, researchers and physicians in Europe but also in Canada, where climate change is fuelling a population explosion of ticks that carry Lyme disease and other vector-borne illnesses. According to some estimates, the number of cases is soaring in the Maritimes and the southern regions of Quebec, Ontario, Manitoba and British Columbia and is more than 13 times the reported total.

Moreover, early detection of Lyme disease is crucial in preventing more serious illness and debilitating chronic symptoms as the bacterial infection progresses.

Thermographic imaging is already a well-established non-invasive tool in neurology, dermatology and the detection of cancer and circulatory diseases. The scientists at Ternopil hope to demonstrate it can play a role in the early diagnosis of tick-borne infections, as well.

How thermography works

The technique uses an infrared camera to detect heat emanating from an object, in this case a human body. It then assigns a colour to signify the temperature range emanating from each area it scans – for example, blue might signify a cooler temperature, while yellow, red and white signify progressively higher levels of heat.

The camera then creates a graphic map so researchers can see where the hottest and coolest areas are.

The researchers scanned 16 patients who had confirmed cases of Lyme disease but no visible rash, hoping to see the inflammation surrounding the tick bite show up visually on the heat map. They also examined a control group of 22 individuals who’d been bitten by ticks but whose blood tested negative for the bacteria that cause the infection.

“In the cases studied, the thermal pattern revealed by this method resembled the typical ring-like shape of the Lyme disease rash, helping to uncover hidden inflammation,” they write.

“These findings suggest that infrared thermography may help identify Lyme disease earlier in patients without visible skin changes, supporting timely diagnosis and treatment.”

It’s just one method researchers are studying in an effort to improve the early diagnosis of tick-borne illnesses. For example, Canadian researchers are testing a biosensor that could detect the bacteria that cause Lyme disease in urine. 

But is thermographic imaging feasible yet as a routine diagnostic tool for primary care physicians?

The equipment is pricey, with medical and research-grade infrared cameras costing in the tens of thousands of dollars, but a study published in the August edition of the Cureus Journal of Medical Science suggests there are other more pressing limitations,

“A recent review of (infrared thermography) in clinical practice highlighted that there are no standardized protocols …with each protocol varying depending on the camera manufacturer,” the authors state.

They also caution that heat maps can vary between men and women and may not be as accurate in individuals who are overweight.

The study from Johns Hopkins Medicine Lyme Disease Research Center suggests you probably won’t find thermal imaging equipment at your family doctor’s office, or in a walk-in clinic, any time soon.

 But it does have other important uses, the researchers write.

“Although infrared thermography is not available in most clinical practices and is unlikely to change routine Lyme disease diagnosis at this time, it could become a valuable research tool,” the article reads. 

The authors say the technology “may deepen scientific understanding of how … infection and inflammation spread in early Lyme disease.”

1.  In 2015, researchers found that only 18% of Canadian paediatric Lyme cases presented a bullseye rash. Another study (PDF) highlights treatment delay when the EM rash is not part of the initial presentation (https://doi.org/10.4269/ajtmh.22-0437).