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A Multiyear Longitudinal Study of Climatic Factors Influencing Ixodes scapularis Phenology and Density in Southwestern Pennsylvania

Young, Ernest J (2023) A Multiyear Longitudinal Study of Climatic Factors Influencing Ixodes scapularis Phenology and Density in Southwestern Pennsylvania. Master's Thesis, University of Pittsburgh. (Unpublished)

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Ixodes scapularis ticks are the major vector, in the eastern United States, for Borrelia burgdorferi sensu stricto, a causative agent of Lyme disease as well as other tick-borne diseases of clinical importance: Anaplasma phagocytophilum, Babesia microti, other Borrelia species, and Powassan virus. Pennsylvania reports the highest yearly incidence rates of Lyme disease to the CDC, yet there are very few multi-year longitudinal studies establishing I. scapularis phenology within the state, including western Pennsylvania, a region between the Northeast and Midwest, regions which differ in I. scapularis phenology profiles. This study examines I. scapularis phenology over two years in six parks in southwestern Pennsylvania. This study reports phenology profiles similar to those which have been reported in the United States Northeast and in west-central Pennsylvania: asynchronous immature life stage activity, but with peaks less temporally distant than what was observed in the Northeast. This study reports significant differences in nymph densities between years and between the parks, with implications that disease risk models of I. scapularis vector-borne diseases should take into account the dynamic landscape of vector prevalence. As saturation pressure deficit, a function of atmospheric humidity, has been implicated as a driver of tick questing activity, this study examines the influence of climatic factors on questing I. scapularis density to test whether these factors influenced seasonal phenology trends. While this study reports that larval questing densities in 2022 positively correlated to humidity-related variables: dew point, vapor pressure, and absolute humidity; no correlation was seen between these variables and larval density in 2021 or nymph densities in either year, suggesting that seasonal behavior patterns are not solely reliant on humidity. Taken together, these studies can be used to inform disease risk models and prevention efforts in southwestern Pennsylvania as part of a public health and One Health approach to vector-borne disease management.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Young, Ernest JEJY13@pitt.eduEJY13
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairTufts, Danielle Mdmt80@pitt.edudmt80
Committee MemberMattila, Joshua Tjmattila@pitt.edujmattila
Committee MemberRichards-Zawacki, Corinne Lcori.zawacki@pitt.educori.zawacki
Committee MemberSimmons, Thomas
Date: 15 May 2023
Date Type: Publication
Defense Date: 21 April 2023
Approval Date: 15 May 2023
Submission Date: 28 April 2023
Access Restriction: 2 year -- Restrict access to University of Pittsburgh for a period of 2 years.
Number of Pages: 64
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Infectious Diseases and Microbiology
Degree: MPH - Master of Public Health
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: infectious disease, black legged tick, deer tick
Date Deposited: 15 May 2023 22:04
Last Modified: 15 May 2023 22:04


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