Comparison of Ixodes scapularis (Acari: Ixodidae) populations and their habitats in established and emerging Lyme disease areas in New Jersey.

Hunterdon Country, New Jersey, experienced a significant increase in the number of Lyme disease cases during 1990-1995, accounting for 21.2% of all New Jersey cases. This study compares the relative abundance of Ixodes scapularis Say in similar habitats in Hunterdon County, an emerging Lyme disease area, and Monmouth County, where Lyme disease has been established for well over a decade. The extent to which differences in habitat physiognomy could explain differences in tick populations, and consequently Lyme disease case rates, is addressed. Ticks were surveyed and vegetation measurements made in 4 habitat types at 1 site in each county. I. scapularis was 7 times more abundant in Monmouth County than in the Hunterdon County site, and the distribution of all life stages among habitats differed significantly between sites. The greater numbers of subadult ticks at the Monmouth County site was attributed to greater shrub cover and litter depth which created more favorable microclimatic conditions for tick survival. However, the overall physiognomy of the different vegetation types at the sites studied in Monmouth and Hunterdon counties was remarkably similar and did not appear to explain differences in tick abundance. Until further research clarifies microscale differences between habitats, the differences in the case rates between the counties appear to be more likely the result of reporting artifact.