Tree House Humane Society offers a solution to deal with the exploding rat problem in Chicago.....it's feral cats! Chicago has dramatically cut down on their rat abatement program, which combined with other factors, has encouraged the city surge in rat numbers. Rats aren't easy to eradicate, they can slip into crevices as wide as their heads, climb vertically, and use our sewers as highways. Poisons typically do work if you hire a private exterminator, but then there's the cost involved and a concern about both the environment and pets (or even children) getting into that poison.
Tree House is a leader among trap, neuter, return programs to control populations of feral (or unsocialized community cats) - overseeing dozens of cat colonies in Chicago. Jenny Schlueter of Tree House realized that if you re-locate a few of the cats to where rats are - the vermin soon disappear, it's putting cats to work.
While it's true some city rats grow to be quite large - about as large as a Volkswagon - and might give a cat a pretty good fight, they'd rather just move on. As smart as rats are, so are cats; they have their ways of catching the big guys, and particularly young rats (helping to control numbers), but most of all their mere presences dissuades rats. As a bonus, they catch mice too.
Aside from being grossed out at the rats, this is a potential serious public health issue. Rats do carry diseases, and when the populations explode a whole host of problems can be created for people as well as our pets, including leptospirosis which may be on the rise in big cities where rats are abundant.
Here's Larry Yellen's report on Fox News Chicago,