Temporal and spatial dynamics of Ixodes scapularis (Acari: Ixodidae) in a rural landscape.

We studied seasonal, interannual, and both small- and large-scale spatial variation in the abundance of blacklegged ticks, Ixodes scapularis Say, in a semirural landscape in southeastern New York. Using transect drag sampling, we found that ticks were approximately twice as abundant in 1994 as in the preceding 2 yr. In 1994, larval ticks showed a strong peak in activity in late spring, coincident with the nymphal peak that year. All post-egg life stages were more abundant in forested than in shrubby or herbaceous habitat types, but peak abundance of larvae shifted from oak-dominated forest in 1992 to maple-dominated forest in 1993 and 1994. All life stages were highly clumped at small spatial scales, but larvae were the most aggregated. Within the forested habitat types, we observed an initial increase followed by a decrease in small-scale clumping during seasonal activity for each life stage. We discuss potential effects of the observed temporal and spatial variation on risk of Lyme disease. Because of pronounced variation in abundance and activity patterns among years and habitat types, we caution against generalizing from short-term or spatially limited studies.

Larval density and feeding success of Ixodes scapularis on two species of Peromyscus.

One potential mechanism for the regulation of tick populations is density-dependent feeding success on vertebrate hosts. In a series of laboratory experiments, we tested whether the density of larval Ixodes scapularis on the mice Peromyscus maniculatus and Peromyscus leucopus influenced tick feeding success. For both host species, the proportion of ticks feeding to repletion was constant (approximately 40-50%) over a range of infestation from 5 to 100 ticks per mouse. For P. leucopus, neither mass nor molting success of fed ticks was significantly related to tick density on the host. However, for P. maniculatus, we observed a statistically significant increase in molting success with increasing tick density on hosts, thus demonstrating facilitation rather than density-dependent regulation. Although results were not statistically significant, we observed a tendency for previously exposed P. leucopus to support lower tick feeding success than naive mice; however, even for previously exposed mice, tick feeding success was not density dependent. Our results do not support the notion that density-dependent feeding on hosts regulates density of I. scapularis populations at the numbers tested.