The effects of vegetation density and habitat disturbance on the spatial distribution of ixodid ticks (Acari: Ixodidae)

Stein, Kenneth J. and Waterman, Megan and Waldon, Jefferson L. (2008) The effects of vegetation density and habitat disturbance on the spatial distribution of ixodid ticks (Acari: Ixodidae). Geospatial health , 2 (2). pp. 241-252. ISSN 1970-7096

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Abstract

Larval, nymphal, and adult Amblyomma americanum (L.), and adult Dermacentor variabilis (Say) ticks were collected using timed dragging techniques, in an attempt to examine how different habitat variables affect models that describe the distribution of ticks in Virginia, USA. Tick count data were modeled using two approaches: (i) habitat and edge, and (ii) habitat, edge, vegetation density and levels of disturbance. Nymphs and adults tended to follow a forest edge distribution when analysed by habitat and edge. Using all variables, we detected a positive relationship with forest edges and negative associations with high-density vegetation. When larvae were modeled by habitat and edge, we failed to detect associations with the edges of habitats. When all variables were included in the larval analysis, disturbed meadow edges emerged as important in the first year, and the categories of disturbed and maturing habitat in the second year. Vegetation density and levels of disturbance were marginally important towards explaining the distribution of nymphs and adults; however, levels of disturbance were potentially more important to the distribution of larvae, than habitat types. Using the habitat and edge variables, and predicted mean encounter rates for all stages of A. americanum and adult D. variabilis, we successfully cross-validated our predictions of high, moderate and low tick densities in both years. The results for nymphs and adults were combined to develop a colour-coded threat assessment map. We estimated that the majority of ticks were located on ~ 20% of the landscape. The potential uses of geographical information system-based threat maps are discussed.

Item Type:	Article
Uncontrolled Keywords:	ixodid ticks, geographical information system, habitat characterization, spatial distribution, predictive modeling.
Subjects:	600 Tecnologia - Scienze applicate > 610 Medicina e salute (Classificare qui la tecnologia dei servizi medici) > 614 Medicina legale; incidenza delle malattie; Medicina preventiva pubblica > 614.4 Incidenza delle malattie e misure pubblica per prevenirle (classificare qui l'Epidemiologia, l'Epidemiologia clinica) > 614.43 Vettori di malattie e malattie trasmesse attraverso l’acqua (classificare qui il controllo delle infezioni che portano malattie) > 614.432 Incidenza delle malattie e misure pubbliche per prevenirle. Vettori di malattie e malattie trasmesse attraverso l’acqua. Insetti 900 Storia, Geografia e discipline ausiliarie > 910 Geografia e viaggi > 910.285 Geographic information systems
Depositing User:	Users 66 not found.
Date Deposited:	22 Jul 2010 09:19
Last Modified:	22 Jul 2010 09:19
URI:	http://eprints.bice.rm.cnr.it/id/eprint/2948

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