Scientists in the US have developed a test to more accurately diagnose Lyme disease, a condition transmitted by black-legged ticks (Ixodes scapularis) infected by a bacterium called Borrelia burgdorferi.
The new test, described in a paper in Science Translational Medicine, is important because Lyme disease is the most common vector-borne illness in Europe and North America. In the US alone there are an estimated 300,000 cases each year. However, false-positive diagnoses are common because the symptoms closely resemble those of another tick-transmitted condition, Southern Tick-Associated Rash Illness (STARI).
It must be noted that the test, devised by a team led by John Belisle from Colorado State University, applies only to “classical” Lyme disease, a well-described condition that in the US is almost completely endemic to just 14 states, produces fever, rash, facial paralysis, and arthritis, and responds well to antibiotics.
Another alleged condition, dubbed “chronic” or “late stage” Lyme disease, is the centre of a multi-million dollar treatment industry in the US and elsewhere. However, evidence for the existence of the condition is strongly contested.
In a February editorial in The American Journal of Medicine, for instance, Yale University epidemiologist Eugene Shapiro described it as “persistent, unexplained subjective symptoms, with no documented history of Lyme disease and without credible laboratory evidence – past or present – of infection with Borrelia burgdorferi.”
The test for standard Lyme disease developed by Belisle and colleagues distinguishes biomarkers arising from changes to metabolite levels. The changes differ between Lyme disease and STARI, enabling more reliable identification.
“The focus of our efforts is to develop a test that has a much greater sensitivity, and maintains that same level of specificity,” Belisle says. “We don’t want people to receive unnecessary treatment if they don’t have Lyme disease, but we want to identify those who have the disease as quickly as possible.”
People found not to have Lyme disease but STARI instead face a harder road back to health. The cause of the illness remains unknown, and treatment by antibiotics, while standard, is thought to be pointless.