UBC Theses and Dissertations
Untangling urban rat-associated health risks in disadvantaged neighbourhoods : from movement to mental health Byers, Kaylee Aileen
Urban Norway rats (Rattus norvegicus) carry a number of pathogens transmissible to people, and the prevalence of these pathogens can vary across fine spatial scales. While pathogen prevalence is an important determinant of human health risk, the transmission of these pathogens to people is closely linked to how rats and humans interact in cities. In this thesis, I investigated how interactions between urban rats, their environment, and people could influence human health risks. To do this, I explored whether rat movement could explain heterogeneous patterns of pathogen prevalence. First, in Chapter 2, I synthesized the published literature and found that rat movement is largely restricted by resource availability and landscape barriers such as roadways. Then, in Chapters 3 – 5, I combined ecological and genomics-based approaches to describe rat movement in Vancouver’s Downtown Eastside, an area where pathogen clustering has been previously documented. In Chapter 3, I demonstrated that movement estimates derived from capture-mark-recapture methods are prone to bias due to smaller individuals more frequently re-entering traps than larger individuals. Given issues of unequal trappability, in Chapter 4, I evaluated the utility of using Global Positioning System tags to track urban rats and found that these tools are currently ineffective due to tag loss and signal obstruction. In Chapter 5, I used rat genetics to identify related individuals and the distances between them. I demonstrated that 99% of highly related rat pairs (i.e., parent-offspring and full-sibling pairs) were trapped in the same city block, revealing infrequent dispersal among blocks, which aligned with patterns of pathogen clustering in this population. Finally, in Chapter 6, I interviewed residents of this neighbourhood about their experiences living with rats and illustrated that frequent and close contact with rats negatively impacted the mental health of residents. Overall, my research suggests that minimal movement of rats may lead to a clustering of rat-associated pathogens. Further, my work reveals that even in the absence of disease, interactions with rats may negatively impact the mental health of those living with them. Together, this information can be used to more effectively manage rat-associated health risks in cities.
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