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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Studies on the vector ecology of the American dog tick, Dermacentor variabilis, (Say) (Acari: Ixodidae) in Manitoba, Canada

Yunik, Matthew 02 September 2014 (has links)
The American dog tick, Dermacentor variabilis, is an obligate blood feeding ectoparasite. This tick is a known vector of pathogens that affect the health of wildlife, humans, and livestock and is abundant in Manitoba. The etiological agent of bovine anaplasmosis, Anaplasma marginale, along with members of the spotted fever group rickettsiae are bacteria that are transmitted by this tick. I examined the distribution of these bacteria in Manitoba’s tick population using molecular techniques. During the eradication of an outbreak of bovine anaplasmosis in Manitoba, there was no evidence the bacterium had spilled over into the tick population. Rickettsia montanensis was detected with a mean prevalence of infection of 9.8% (range, 0.00 - 21.74% among localities) in 8 of 10 localities within the province. It was also determined that 19.9% (SE ±1.14) of adult questing ticks collected in one vector season overwintered through to the next spring.
2

Spatial distribution modeling of Dermacentor variabilis ticks under current and future climate change scenarios

Boorgula, Gunavanthi Devi Yadav January 1900 (has links)
Master of Science / Department of Diagnostic Medicine and Pathobiology / Ram K. Raghavan / Dermacentor variabilis (Say) (Acari: Ixodidae), commonly known as the American dog tick is a medically important tick species in N. America, which has been implicated as a competent vector for several diseases, including tularemia, bovine anaplasmosis and canine tick paralysis. This tick is also the primary suspect for the transmission of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF). The spatial distribution and geographic extent of D. variabilis territory in N. America is suspected to have changed in the recent times due to natural and anthropogenic, non-stationary forces. A clear understanding of the spatial distribution and environmental factors contributing to the distribution has public health significance, allowing us to make informed management decisions and for setting robust future research goals aimed at understanding vector-biology and disease management. Additionally, ongoing climate-change is expected to alter species spatial distribution and abundance within distribution range. In this research, I studied the current and likely future spatial distribution of D. variabilis ticks in N. America based on two representative concentration pathways, RCP 4.5 and RCP 8.5, representing lower and higher emission scenarios, respectively, under several global circulation models (GCM). The spatial distribution models were constructed using MaxEnt program and BioClim data was used as environmental data for modeling. Best models were selected based on Partial ROC curves, AIC, and omission rates. Median prediction of these models indicate a wider spread of D. variabilis from its currently known extent, and much further spread as a result of climate change. Different environmental variables that significantly influenced current and future D. variabilis distribution included annual mean temperature, mean diurnal range, maximum temperature of the warmest month, annual precipitation, precipitation seasonality, and precipitation of the wettest quarter.

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