Comparison of direct fluorescent antibody staining and real-time polymerase chain reaction for the detection of Borrelia burgdorferi in Ixodes scapularis ticks.

Borrelia burgdorferi, the agent responsible for causing Lyme disease in humans and animals, is transmitted via the bite of infected Ixodes spp. ticks. Ticks removed from humans and animals are routinely tested by diagnostic laboratories to determine if they are infected with these bacteria. The objective of this study was to compare the efficacy of 2 commonly used methods, direct fluorescent antibody staining and real-time polymerase chain reaction (PCR), for the detection of B. burgdorferi in Ixodes scapularis ticks. One hundred and twenty-seven adult I. scapularis ticks collected in Connecticut, a Lyme disease endemic area, were tested, and results were compared. Results showed 24.8% ticks tested positive for Borrelia spp. by fluorescent antibody testing and 32.5% ticks were positive for B. burgdorferi by real-time PCR testing. When ticks were grouped into categories by level of engorgement (unengorged, partially engorged, and fully engorged), 95% of unengorged ticks, 90.5% of partially engorged, and 86.8% of engorged ticks tested were in agreement. Ten of the 127 ticks examined were too dehydrated to be tested by the fluorescent antibody technique; half of these tested positive by PCR. Real-time PCR appears to be the better of these 2 methods for the diagnosis of this bacterial infection in I. scapularis ticks.