Comparison of the bacteria within ticks from allopatric and sympatric populations of Dermacentor andersoni and Dermacentor variabilis near their northern distributional limits in Canada

Understanding the ecology and epidemiology of tick-borne diseases requires detailed knowledge of the complex interactions among the tick vector, the microorganisms they carry and the vertebrate hosts used by ticks, as well as the environmental conditions experienced by all three groups of organisms in this triad. In this thesis, I addressed questions relating to the biology and vector ecology of the Rocky Mountain wood tick (Dermacentor andersoni) and the American dog tick (Dermacentor variabilis). Comparisons were made of the distribution of both tick species, the vertebrate hosts used by immature ticks, and the types and prevalence of bacteria in individual ticks from multiple localities near the northern extent of their geographic ranges in western Canada. The results revealed that the distributions of both D. andersoni and D. variabilis have expanded since the 1960s, and there is now a broad zone of sympatry in southern Saskatchewan. In this zone of sympatry, D. andersoni and D. variabilis immatures were found to use the same species of small mammals as hosts and, in some cases, the same host individuals. This provides for the possibility of cross-transmission of bacteria from one tick species to the other. Bacteria of several genera (e.g. Rickettsia, Francisella, Arsenophonus and Anaplasma) were detected in D. andersoni and/or D. variabilis, some of which represented new tick-bacteria associations. However, most bacterial species were highly host (tick)-specific, except for three examples of apparent host switching from one tick species to the other at localities where the two tick species occurred in sympatry. The findings of this thesis provide a basis for understanding microbial transmission, the structure of tick-borne microbial communities, the risk of tick-borne disease in humans and animals, and the vector potential of D. andersoni and D. variabilis in geographical areas where they have not been studied previously

Molecular Characterization of Haemaphysalis Species and a Molecular Genetic Key for the Identification of Haemaphysalis of North America

Haemaphysalis longicornis (Acari: Ixodidae), the Asian longhorned tick, is native to East Asia, but has become established in Australia and New Zealand, and more recently in the United States. In North America, there are other native Haemaphysalis species that share similar morphological characteristics and can be difficult to identify if the specimen is damaged. The goal of this study was to develop a cost-effective and rapid molecular diagnostic assay to differentiate between exotic and native Haemaphysalis species to aid in ongoing surveillance of H. longicornis within the United States and help prevent misidentification. We demonstrated that restriction fragment length polymorphisms (RFLPs) targeting the 16S ribosomal RNA and the cytochrome c oxidase subunit I (COI) can be used to differentiate H. longicornis from the other Haemaphysalis species found in North America. Furthermore, we show that this RFLP assay can be applied to Haemaphysalis species endemic to other regions of the world for the rapid identification of damaged specimens. The work presented in this study can serve as the foundation for region specific PCR-RFLP keys for Haemaphysalis and other tick species and can be further applied to other morphometrically challenging taxa

Prevalence of Rickettsia Species in Canadian Populations of Dermacentor andersoni and D. variabilis▿

We determined the prevalence of rickettsiae in Dermacentor adults at 15 localities in Canada. Rickettsia rickettsii was not detected in any tick, whereas Rickettsia peacockii was present in 76% of Dermacentor andersoni adults and Rickettsia montanensis in 8% of Dermacentor variabilis adults. This host specificity was maintained in localities where both tick species occurred in sympatry

Anaplasma bovis–Like Infections in Humans, United States, 2015–2017

We detected the DNA of an Anaplasma bovis–like bacterium in blood specimens from 4 patients from the United States with suspected tickborne illnesses. Initial molecular characterization of this novel agent reveals identity to A. bovis–like bacteria detected in Dermacentor variabilis ticks collected from multiple US states