Assessment of a screening test to identify Lyme disease risk.

BACKGROUND

Lyme disease is emerging in eastern and central Canada due to the spread of the tick vector Ixodes scapularis. Currently, the test to establish Lyme disease-endemic areas requires multiple site visits and multiple sampling methods, and is consequently complex, time-consuming, and resource-expensive.

OBJECTIVE

To assess the capacity of drag sampling alone as a screening technique to identify areas of Lyme disease risk.

METHOD: We conducted a retrospective analysis of field surveillance data obtained at 100 site visits in 2007 and 2008 in southern Quebec.

OUTCOME: Drag sampling used alone had 50% sensitivity but 86% specificity to identify early-established I. scapularis populations. Ticks were found throughout the period May to October.

CONCLUSION

One site visit of drag sampling of three person-hours between May and October may be sufficient to identify a Lyme disease risk location. This information can be used by public health professionals to develop public health responses and by medical practitioners to assist in the clinical diagnosis of Lyme disease.