Ticks are second only to mosquitos as vectors of human infectious diseases worldwide.1 It has been estimated that there are >800 species of ticks worldwide, with >90 species found in the United States.1 Although relatively few tick species bite and transmit disease, those that do can transmit any number of diseases. Among these, Lyme disease is the most prevalent in the United States and Europe.2 It is typically transmitted by deer ticks and blacklegged ticks harboring the spirochete Borrelia burgdorferi. However, ticks can serve as reservoirs and vectors of a vast array of other pathogens, including rickettsiae and other bacteria, viruses, and protozoa; thus, new tick-related diseases and disorders continue to emerge.
Whether the tick bite results in a well-known disease like Lyme disease or a more obscure disorder, tick-related ailments remain difficult to diagnose, particularly in their earliest stages. Patients often have nonspecific symptoms and might not recall having been bitten by a tick or make the association because their symptoms did not manifest until many weeks or months after the bite. Even when a tick-related illness is suspected, many testing challenges remain.
In the setting of Lyme disease, the currently used method employs a 2-tier algorithm. First, an enzyme immunoassay (EIA) is performed, and if the result is positive or borderline, a Western immunoblot is undertaken to increase specificity.2 This method has low sensitivity during early infection, when treatment is most likely to be curative and prevent debilitating complications (eg, neurologic problems, arthritis, carditis).2 Furthermore, current assays do not distinguish between active and inactive infection, the latter of which does not require antibiotic treatment.2 This is problematic given that patients can remain seropositive for years following infection.2
Infectious Disease Advisor had the opportunity to discuss recent advances in testing for Lyme disease and other tick-borne diseases with 2 experts in the field: Rafal Tokarz, PhD, associate research scientist, Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, and Steven Schutzer, MD, professor and physician-scientist, Department of Medicine, Rutgers New Jersey Medical School, Newark, New Jersey. Both interviews were conducted by email exchange and compiled for this article.
Infectious Disease Advisor: Assays that can detect infection from multiple tick pathogens appear to represent a major advance in tick-borne disease testing. Dr. Tokarz, you and your colleagues at Columbia University developed such a test, the Tick-Borne Disease Serochip (TBD Serochip), which was recently detailed in an article in Scientific Reports.3 Currently, the test can identify and distinguish between B burgdorferi, the spirochete responsible for Lyme disease, and 7 other tick-borne pathogens. Can you tell us how the TBD Serochip works?
Rafal Tokarz, PhD: The TBD Serochip is a serologic test that detects the presence of antibodies to a pathogen in the blood. Our approach identifies short, specific regions on pathogens that our antibodies recognize. By identifying all these regions, using them together, and focusing only on them, we make our test very specific to the agent for which we are testing. Our test is also, to my knowledge, the lone serologic test that can simultaneously test for several tick-borne agents at once by using these short, specific non-cross-reactive regions. This enables us to identify patients who have a concurrent infection with more than one pathogen. We have identified samples where individuals were coinfected with agents of Lyme disease and anaplasmosis or Lyme disease and babesiosis. In addition, we can identify past exposure to these agents, meaning that we can detect whether a patient was infected with the pathogen in the past. We’ve seen a number of samples where there is evidence that the patient was exposed to more than one agent of tick-borne disease.
Infectious Disease Advisor: Do you think the TBD Serochip will eventually replace the 2-step algorithm that has been the standard in diagnosing Lyme disease since the 1990s?
Dr Tokarz: The ultimate goal is to supplant the currently employed tests for tick-borne diseases. Our article summarized our initial proof-of concept work.4 Although our test works quite well, we are still validating it and are trying to make it even more comprehensive by including additional agents that we did not include in the first version of the test. While we want to make this test available to the public, what we are really aiming for is to make a much more streamlined and simpler version of this test so that it could be made available to all clinical laboratories and not just specialty diagnostic laboratories.
Infectious Disease Advisor: When do you anticipate your multiplex test would become available?
Dr Tokarz: It is difficult to say, although we aim to have a streamlined test available within the next year or so.
Infectious Disease Advisor: Dr. Schutzer, according to you and your colleagues’ recently published article in Clinical Infectious Diseases,4 a major advance in Lyme disease testing has been next-generation combination EIAs. How are these different from traditional EIAs?
Steven Schutzer, MD: They can be the same. The newer ones can use very specific parts of the target antigens that are not cross-reactive with other microbes, decreasing chances for a false positive, and at the same time can include target antigens that are expressed in an actual infection. These 2 elements were not appreciated when the 1994 Dearborn criteria for diagnostics were formed. Now they can be incorporated into today’s tests. Use of a combined EIA may eliminate the need for a more subjective Western blot. A newer EIA multiplex (several B burgdorferi antigens and their epitopes) has the potential to be done as a single-tier test. Broad-based clinical assessment of these EIAs can be done by a machine. The Western blot is commonly interpreted by an individual; thus, it may be more subjective.
Infectious Disease Advisor: Besides multiplex assays and next-generation EIAs, are there any other testing advances of which healthcare providers should be aware?
Dr Schutzer: Healthcare providers can monitor progress on direct tests that indicate active infection, such as those that identify the pathogen’s nucleic acid (eg, DNA or RNA). The methods are at hand and currently in development for Lyme disease.
Infectious Disease Advisor: Until these new tests become available, how can Lyme disease testing accuracy be improved using currently available testing methods?
Dr Tokarz: Until a blood test comes along that is comparable to the current 2-tiered test, and importantly, just as cost-effective and easy to use, we will be saddled with the 2-tiered test. There are alternative tests being used, however, and we will try to implement ours as well. Eventually, the 2-tiered test will be superseded by a better test.
Dr Schutzer: We will likely need to perform a battery of tests — some that detect early and active infection and some that can detect at least exposure to the pathogen at a slightly later time after infection (eg, antibody tests).
- Parola P, Raoult D. Ticks and tickborne bacterial diseases in humans: an emerging infectious threat. Clin Infect Dis. 2001;32(6):897-928.
- Marques AR. Laboratory diagnosis of Lyme disease: advances and challenges. Infect Dis Clin North Am. 2015;29(2):295-307.
- Tokarz R, Mishra N, Tagliafierro T, et al. A multiplex serologic platform for diagnosis of tick-borne diseases. Sci Rep. 2018;8(1):3158.
- Branda JA, Body BA, Boyle J, et al. Advances in serodiagnostic testing for Lyme disease are at hand [published online December 7, 2017]. Clin Infect Dis. doi: 10.1093/cid/cix943