Overwintering survival of nymphal Ixodes scapularis (Acari: Ixodidae) under natural conditions

Jesse L Brunner; Mary Killilea; Richard S Ostfeld

doi:10.1603/ME12060

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Overwintering survival of nymphal Ixodes scapularis (Acari: Ixodidae) under natural conditions

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Overwintering survival of nymphal Ixodes scapularis (Acari: Ixodidae) under natural conditions

Jesse L Brunner, Mary Killilea and Richard S Ostfeld

Journal of medical entomology, Vol.49(5), pp.981-987

09/2012

DOI: https://doi.org/10.1603/ME12060

Handle:

https://hdl.handle.net/2376/113227

PMID: 23025177

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Abstract

New York

Nymph - physiology

Cold Temperature

Animals

Ixodes - physiology

Mortality

Blacklegged ticks (Ixodes scapularis Say) are exquisitely sensitive to very cold and dry conditions. For this reason it has long been assumed that climatic differences among locations and within microhabitats have a strong influence on variation in their survival over winter. This assumption, however, rests largely on laboratory exposures and on broad-scale associations between climatic variables and the observed distributions of ticks. We present the results of a study of the overwintering survival of I. scapularis nymphs in their natural environment from October through May in two locations in New York State using a repeated sampling strategy to determine when mortality occurred, and whether those events coincide with extreme conditions. We then fit these data to a simple, flexible statistical model in which the hazard of mortality varies with measurable conditions, here minimum daily temperature and mean daily relative humidity. Regardless of winter conditions, > 80% of ticks survived at both sites. A model with constant hazard (i.e., independent of temperature and humidity) was best supported by the data. Although models with hazard increasing at temperatures below 0 deg C and at > 90% relative humidity provided slightly better fits to the data, these models were less parsimonious. These results weaken the expectation that cold-related overwintering mortality necessarily plays a major role in restricting populations of these ticks and thus, risk of tick-borne zoonoses.

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Title: Overwintering survival of nymphal Ixodes scapularis (Acari: Ixodidae) under natural conditions
Creators: Jesse L Brunner - School of Biological Sciences, Washington State University, Box 644236, Pullman, WA 99164-4236, USA. jesse.brunner@wsu.edu
Mary Killilea
Richard S Ostfeld
Publication Details: Journal of medical entomology, Vol.49(5), pp.981-987
Academic Unit: Biological Sciences, School of
Publisher: England
Grant note: R03 A10795-46-0 / PHS HHS
Identifiers: 99900547624101842
Language: English
Resource Type: Journal article