Effects of Culling on Leptospira interrogans Carriage by Rats - PubMed (original) (raw)

Effects of Culling on Leptospira interrogans Carriage by Rats

Michael J Lee et al. Emerg Infect Dis. 2018 Feb.

Abstract

We found that lethal, urban rat control is associated with a significant increase in the odds that surviving rats carry Leptospira interrogans. Our results suggest that human interventions have the potential to affect and even increase the prevalence of zoonotic pathogens within rat populations.

Keywords: Canada; Leptospira interrogans; Norway rat; bacteria; carriage; culling; leptospirosis; rats; rodent control; zoonoses.

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Figures

Figure 1

Figure 1

Two example sites side-by-side in a study of the effects of culling on Leptospira interrogans carriage by rats, Vancouver, British Columbia, Canada, June 2016–January 2017. Each site comprised 3 city blocks connected by continuous alleys; individual sites that were trapped at the same time had parallel alleys separated by major roads and multiple buildings that, based on previous research (9 , 10), rats were assumed to be unlikely to move between. Five and 7 sites were randomly selected as intervention and control sites, respectively. In intervention sites, kill-trapping was conducted in the center of the 3 blocks; blocks flanking the intervention block were designated nonkill flanking blocks (nonkill flanking blocks were trapped to detect any indirect effects of kill-trapping, such as immigration from/emigration to the intervention block). Image downloaded from Google Earth Professional (

https://www.google.com/earth/download/gep/agree.html

).

Figure 2

Figure 2

Experiment timeline in intervention and control sites in a study of the effects of culling on Leptospira interrogans carriage by rats, Vancouver, British Columbia, Canada, June 2016–January 2017. Trapping in each intervention site was divided into three 2-week periods: the period before kill-trapping, the period during kill-trapping, and the period after kill-trapping. During the 2 weeks before kill-trapping, we captured and sampled rats, gave them all a unique ear-tag identifier, and then released them where they were caught. In the following 2 weeks (the kill-trapping period) rats that were caught in the center of the 3 blocks were euthanized; catch-release continued in flanking blocks. Traps were then removed for

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3–6 weeks, after which they were returned to their exact prior locations, and capture-sample-release continued for 2 more weeks (the period after kill-trapping). The trapping protocol was the same for control blocks except that capture-sample-release was conducted during all 2-week trapping periods. Prebaiting (during which traps were fixed open) was used to acclimate rats to cages (Technical Appendix).

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