reference : Seasonal activity patterns of Ixodes pacificus nymphs in relation to climatic conditions

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Bibliographic fields
reftype Journal Article
Abstract In western North America, the tick Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) is the primary vector to humans and domestic animals of the disease agents causing Lyme disease and granulocytic ehrlichiosis. We examined the seasonal activity patterns of I. pacificus nymphs over a 4-year period, including the wet and cold El Nino winter/spring of 1998, in a dry oak/madrone woodland, and for one year in a cooler and moister redwood/tanoak woodland in Mendocino County, California. Linear regressions were used to estimate when nymphal densities first exceeded and then fell below 25, 50 and 75% of the recorded yearly peak densities. In oak/madrone woodland, nymphs typically were active by mid-March, reached 50% of their yearly peak densities in early to mid-April, peaked by early May, fell below 50% of their peak densities by early to mid-June, and were absent by late July to mid-August. The lengths of the periods with nymphal densities exceeding 50 and 75% of the recorded yearly peaks in oak/madrone woodland were associated positively with rainfall and negatively with maximum air temperatures during April-May. Moreover, nymphal numbers typically reached 50% of their peak 10-15 days later, remained at levels above 50% of the peak 1.3-1.5 times longer, and started declining 4-6 weeks later under cooler, moister climatic conditions (oak/madrone woodland in 1998 and redwood/tanoak woodland in 2000) relative to warmer, drier conditions (oak/madrone woodland in 2000-2001). In oak/madrone woodland, nymphal densities typically started to decline when mean maximum daily air temperatures exceeded 23degreesC. Nymphal densities were higher in dry oak/madrone relative to moist redwood/tanoak woodland from mid-March to late May 2000, similar in both habitat types in early June, but higher in redwood/tanoak woodland from late June onwards. We conclude that large-scale studies of the density of I. pacificus nymphs in California need to consider spatial variation in the length of nymphal activity periods and select temporal sampling regimens that yield representative data for all included habitat types.
Author Eisen, L.; Eisen, R. J.; Lane, R. S.
DOI 10.1046/j.1365-2915.2002.00372.x
Date Jun
ISSN 1365-2915
Issue 3
Journal Medical and Veterinary Entomology
Keywords borrelia burgdorferi; ixodes pacificus; climate; ecology; habitat; lyme disease; nymphs; risk index; seasonality; california; USA; blacklegged tick acari; black-legged tick; lyme-disease; borrelia-burgdorferi; ixodidae nymphs; scapularis acari; new-jersey; california; temperature; survival
Language English
Notes 589TF Times Cited:35 Cited References Count:32
Pages 235-244
Title Seasonal activity patterns of Ixodes pacificus nymphs in relation to climatic conditions
Volume 16
Year 2002
Bibliographic identifiers
.reference_type 0
_record_number 17734
_uuid 4902bb7e-2914-469b-b0ee-06dc728f00c5