At night, a sea of rats can be seen overtop of horse manure piles. Inside the stables, they crawl atop gates, scurry from stall to stall, and burrow beneath the ground.

That's according to Donna Scrannage, a decades-long horse owner and user of the Fraser Downs racetrack in Surrey, where she says the infestation began about five years ago and has only gotten worse.

"They're in their feed tubs. They're in their water buckets. They're in the stalls constantly," she told CBC News. "They wreak a lot …