Since the 1950s, Alberta has boasted about being rat-free, as an aggressive rat control program kept the vermin outside of the borders.
Exterminators have killed 19 rats in and around the Medicine Hat city landfill since Wednesday.
Minister of Agriculture Verlyn Olson says the province is taking the sighting seriously and will help local crews with exterminating any other rats.
“This is certainly not the first time a rat has been spotted in Alberta, and it won't be the last time,” says Olson.
“It would be naive to think that no rat ever set foot in Alberta. Rats don't respect provincial borders. But the key is as soon as we find evidence we act very quickly and very aggressively."
It's estimated one pair of reproducing rats could lead to a colony of 15,000 rats in a year, says Olson.