Seasonal activity and spatial distribution of host‐seeking adults of the tickDermacentor variabilis

Abstract

The seasonal temporal and spatial distribution and emergence of overwintering and summer cohorts of host-seeking American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae), adults were examined for 5 years in the Bluegrass region of Kentucky. Weekly drag cloth sampling was conducted from early March until late September 1992-1995 and early March until the end of May 1996. Overwintering adult cohorts became active in early to mid-April followed by bimodal host-seeking activity each year, with the duration and intensity of the first activity period being related to the previous year's summer cohort activity. The first activity peak extended from mid-April through late May and the second activity peak occurred in July. All host-seeking activity ceased by early August, except in 1995, when activity ended on 22 August. Laboratory survival of adults, collected weekly during 1993-1996, was used to estimate the emergence of summer adult cohorts. Summer adult cohorts became active in late May or early June and overlapped with overwintering adult host-seeking activity. The termination of host-seeking activity in overwintering adults could not be determined using the methods employed in this study and is most likely to have continued for the entire season. Host-seeking adults displayed contagious distribution patterns along trails bordering ecotone habitats, as determined by fitting a negative binomial frequency distribution to weekly sampling data. These patterns did not vary from year to year. In addition, the location of D. variabilis activity did not change from year to year, which suggests that microhabitats within apparently homogeneous environments enhance adult survival and lead to 'hot spots' of tick activity despite the ability of vertebrate hosts to disperse D. variabilis populations more widely. These data better define our understanding of D. variabilis adult seasonal and spatial host-seeking activity, estimate for the first time the intensity of summer cohort host-seeking activity, and relate summer cohort activity with spring activity the following year.

National Surveillance of Spotted Fever Group Rickettsioses in the United States, 2008–2012

“…23,24 This trend varied widely by region with some areas, such as the west and northeast, showing no distinct seasonality. Year-round moderate temperatures and longer periods of tick-feeding activity, such as those observed in Arizona and California, may account for less characteristic seasonal distribution in warmer areas.…”

The Role of Ecotones in Emerging Infectious Diseases

“…Mosquitoes responsible for the transmission of encephalitis virus have been found to congregate at ecotones (Lothrop et al, 2002), and populations of competent rodent reservoirs (whitefooted mouse) for Lyme disease preferentially inhabit ecotones (LoGiudice et al, 2003). Ecotones have been identified as potentially important for some eukaryotic parasites in terms of host seeking (Burg, 2001) and host switching (Hoberg et al, 2002). The pathogenÕs themselves may concentrate in their host populations at ecotones as is apparent for some arboviruses (Yuill, 1986).…”

An Acarologic Survey and Amblyomma americanum Distribution Map with Implications for Tularemia Risk in Missouri

“…Within specific vegetation types, ticks may aggregate in optimal host-seeking habitat or specific microhabitats, which may potentially skew the abundance data. 13,21 Dichotomizing the data helps to control for these effects and preserves the core trends of the data.…”

“…Our spring sampling period coincided with the peak seasonal activity of Amblyomma americanum nymphs and adults and Dermacentor variabilis adults. [21][22][23][24] Site selection. Using the 1996 Missouri Gap Analysis Program land classification maps ( http://msdis.missouri.…”