Rats carry many pathogens and dealing with them gets complicated. Photo: istock.

Rat race! How pest control can backfire

Rats are popular in horror stories. But unlike ghosts and goblins, getting rid of them is more difficult than calling Ghostbusters. Science has better options.

UBC Science
Oct 23 · 5 min read

By Kaylee Byers, UBC Interdisciplinary Studies, The Vancouver Rat Project

If you live in a major city, chances are you’ve seen rats scurrying around dumpsters or along alleyways. Urban rats are found around the world, and wherever they go, people work to get rid of them — and for good reason. Rats are infamous for their ability to carry a number of “pathogens,” or disease-causing organisms. They can also infest our homes, damaging infrastructure and keeping us up at night. But what if our approaches to pest control actually increase some rat-associated risks?

Who you gonna call?

Kaylee Byers. Photo: UBC.

New rats on the block

Round up all the rats? It’s not so simple

Electronic image of Leptospira interrogans. Photo: CDC/NCID/HIP/Janice Carr (PHIL #1220).

We found that after a pest-control intervention, rats were more likely to carry Leptospira than they were before pest control. This increase in disease-carrying rats only occurred in blocks where a pest control intervention was done. Because Leptospira is spread among rats via contact with other rats and their urine, we believe removing individuals from a population could change normal patterns of social interactions among rats. Removing an individual at the top of the social hierarchy (dominant) may result in a re-negotiating of social structure which results in increased aggression among rats which, in turn, increases pathogen spread. Pest control could actually increase the number of rats carrying a disease-causing bacterium and therefore increase your risks of coming into contact with a pathogen-carrying rat.

It’s a marathon

Kaylee Byers. Photo: UBC.

Perhaps we should change our focus altogether. Eradication as the sole aim of a rat control program is likely to be met with disappointment. Rats adapt quickly, reproduce rapidly and are very resistant to most of the pest control approaches we’ve thrown at them. Instead, what if we consider rats not as invaders, but as a part of cities?

By viewing rats as part of the urban ecosystem, we can manage the environmental conditions which make areas particularly vulnerable to rats, instead of focusing on the rats themselves. In Vancouver’s Downtown Eastside, rat encounters are common in single room occupancy hotels, where ageing infrastructure allows rats to move easily between rooms and through hallways. Using an ecosystem approach, rat management could involve improving access to and quality of housing in the Downtown Eastside instead of solely focusing on baiting and trapping. This shift would improve the rat-resiliency of neighbourhoods and cities, but requires strategic, long-term investment.

The science is telling us that our current approaches are not working. Are we ready to listen?

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Focus: Stories from the Faculty of Science at the University of British Columbia

Thanks to Koby Michaels

UBC Science

Written by

Stories from the Faculty of Science at the University of British Columbia | Edited by Silvia Moreno-Garcia, assistant editor Koby Michaels | science.ubc.ca


Focus: Stories from the Faculty of Science at the University of British Columbia

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