A new PCR test has been developed for the early diagnosis of Lyme disease. The test detects a gene belonging not to the bacteria that causes the disease, but to a specific bacteriophage. If the bacteriophage is detected, then the bacteria is also present, according to scientists from the University of Leicester (UK).

Lyme disease, or borreliosis, is an infectious disease transmitted by ticks. It is characterized by skin lesions such as erythema migrans, as well as damage to the nervous system, musculoskeletal system, and heart. Over the past two decades, Lyme disease has become widespread in North America and Europe (particularly Ukraine), and its incidence continues to rise.

Modern tests for diagnosing Lyme disease are based on the detection of antibodies to the causative agent, the bacterium Borrelia burgdorferi . However, antibodies only appear several weeks after infection. This means that in the early stages, a diagnosis cannot be confirmed by laboratory testing. At the same time, the first stage of the disease can be asymptomatic: without prompt diagnosis and treatment, the infection will progress, and within a few months, symptoms of the much more serious second stage, affecting joints, the nervous system, and other organs, may appear. Therefore, early diagnosis of Lyme disease in individuals bitten by a tick is essential.

Researchers have tested* a new approach to molecular diagnostics of Lyme disease: they decided to hunt for the gene of a specific bacteriophage, rather than the causative bacteria. They noted a high correlation between the presence of the bacteriophage and B. burgdorferi in the body. Moreover, the number of bacteriophage particles in the blood of infected people is 10 times higher than the number of B. burgdorferi bacteria, facilitating the detection of the target gene in a PCR test.

Importantly, the number of copies of the terL phage gene, which the researchers determined using PCR, can differentiate between the early stage (fewer copies) and late stages (more copies) of the disease. Uninfected individuals have the lowest number of phage gene copies.

The authors believe that this test will radically change the early diagnosis of Lyme disease and help prevent the serious consequences of an undetected illness. Furthermore, the test could be used to monitor the effectiveness of Lyme disease treatment.

Before the test can be introduced into clinical practice, it still needs to undergo a series of clinical trials and validation.

* Shan J, Jia Y, Teulières L, Patel F, Clokie MRJ. Targeting Multicopy Prophage Genes for the Increased Detection of Borrelia burgdorferi Sensu Lato (sl), the Causative Agents of Lyme Disease, in Blood. Front Microbiol. 2021;12:651217. doi:10.3389/fmicb.2021.651217