It is not surprising that there has been considerable interest in an Clinical Infectious Diseases Advance Access article published online on February 11, 2014, “Xenodiagnosis to Detect Borrelia burgdorferi Infection: A First-in-Human Study.” The lead author of the study is Adrianna Marques, National Institute of Allergy and Infectious Diseases, NIH. LDA has a particular interest in this study because co-author Linden T. Hu, MD, Department of Medicine, Tufts Medical Center, Boston, MA, will be making a presentation on the study at the scientific conference, jointly sponsored by the Columbia University College of Physicians & Surgeons and the Lyme Disease Association, Inc., to be held on May 3-4, 2014, in Providence, RI. LINK TO CONFERENCE REGISTRATION
A total of 36 subjects were enrolled in the study, including 10 patients with high C6 antibody levels, 10 patients with PTLDS, 5 patients with EM after completion of antibiotic therapy, 1 patient with EM on therapy, and 10 healthy volunteers. Not all of the tick placements yielded enough blood-engorged for testing, but 23 volunteers with Lyme disease had at least one tick tested. Of those, 19 tested negative, and results were indeterminate in 2 patients attributed to lab contamination. Results were positive for B. burgdorferi DNA in one patient with PTLDS and in the patient with EM early during therapy.
It should be pointed out that the patient with EM early during therapy, who was one of the two positives for Borrelia DNA, was included in the study as a “possible positive control.” This patient had EM diagnosed by a study physician and started antibiotic therapy concomitantly with tick placement; ticks were collected at the end of the fourth day of antibiotic therapy. The authors stated that although individuals with untreated EM would be a better control, they felt it would be inappropriate to withhold treatment during tick feeding.
The objective of the overall study is to determine whether xenodiagnosis can be used to successfully investigate the presence of Lyme disease bacteria. According to Dr. Marques, the primary goals “in this initial trial were to develop procedures for tick xenodiagnoses and to determine its safety in humans.”
A primary conclusion of the initial study was that xenodiagnoses using Ixodes scapularis larvae on humans was safe and well tolerated. Another conclusion was that “Further studies are needed to determine the sensitivity of xenodiagnoses in patients with Lyme disease and the significance of a positive result.”
Having Dr. Hu present the study findings in this academic setting, the LDA/Columbia Lyme conference, will enable attendees to learn more about the study and the subject of xenodiagnoses in humans and its possible impact in the field of tick-borne diseases and will enable scientists and physicians to pose questions on study design and conclusions.