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UBC Theses and Dissertations

The impacts of kill-trapping on carriage of Leptospira interrogans and methicillin-resistant Staphylococcus aureus by wild rats in Vancouver's Downtown Eastside Lee, Michael Joseph


The ecology of wild urban rats is an important determinant of the transmission and carriage of rat-associated zoonoses (RAZ). For example, previous research has shown that RAZ are clustered in rat populations at the level of the city-block, possibly because rats, which rarely move beyond a single city-block, live in colonies that do not interact with rats from other colonies. It may therefore be the case that rat colonies self-limit the spread of RAZ to within the infected colony. Because anthropogenic disturbances can disrupt animal ecology, I hypothesized that human disruptions of typical rat ecology, such as pest-control, can also disrupt the epidemiology of RAZ within the disturbed rat population. This dissertation tests the hypothesis that kill-trapping wild urban rat populations can lead to unpredictable changes in RAZ epidemiology, even leading to increases in the transmission and/or spread amongst rat populations. This work tested rats for Methicillin-resistant Staphylococcus aureus (MRSA) and Leptospira interrogans both before and after enacting a kill-trapping intervention at the level of the city-block in Vancouver Canada’s Downtown Eastside (DTES). Study blocks were categorized as either intervention blocks (in which kill-trapping was enacted), non-kill flanking blocks (blocks immediately next to intervention blocks in which no kill-trapping was enacted), and control blocks (in which no kill-trapping was enacted). Rats caught after kill-trapping in intervention blocks had 9.55 (95% CI 1.75-78.31) times the odds of carrying Leptospira interrogans than did rats that were caught in any block type before the intervention. This effect was not observed in any other block type for Leptospira interrogans or for carriage of MRSA. These results indicate that kill-trapping may impact the odds that rats that survive the killtrapping carry some RAZ.

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