Lyme Disease: Where it is and isn't

In my outpatient practice, I commonly see patients referred with a diagnosis of Lyme Disease. However, the overwhelming majority of these patients do not have an illness consistent with this infection. Most have negative serology, although the negative serology is not infrequently misinterpreted  by the referring physician (e.g., I commonly see patients who may have a single band positive on a western blot IgG, which does not meet diagnostic criteria for Lyme Disease but the "positive" band is circled on the lab sheet by the doctor and the patient comes to see me). Other patients do have positive western blots by CDC criteria, yet the clinical picture is not consistent with Lyme Disease. Over the 16 years I have worked in Richmond, I can recall only one patient that I thought truly had Lyme Disease and in this patient the tick bite had occurred elsewhere in a highly endemic area. The problem, of course, is when you are faced with a positive test and a patient who has symptoms, even atypical ones, there is often a bias towards treatment. Unfortunately, much of the epidemiology of Lyme Disease is based on diagnostic testing that remains inaccurate.

So I was almost euphoric when I saw a new paper in the American Journal of Tropical Medicine and Hygiene that took a very different approach in elucidating the epidemiology of Lyme Disease. In this CDC-funded study, over 5,000 Ixodes scapularis ticks from the 37 states where the tick is found (upper midwestern and eastern US) were tested for Borrelia burgdorferi, the causative agent of Lyme Disease. Based on the data collected a risk map was constructed:

The map shows two major foci of infected ticks--the eastern seaboard from northern Virginia to Maine, and the upper midwest with a concentration in Wisconsin and Minnesota. Interestingly, no infected ticks were found in central Virginia, which confirms my clinical observation. Nonetheless, we desperately need better diagnostic testing for Lyme Disease.

Map:  NPR