They were primarily responsible for the spread of the Black Death/Great Plague, one of the worst pandemics in human history, so yes. And I'd like to point out that the plague still exists[1]. Now imagine what could happen if we just gave rats free rein... I'm all for animal rights and sympathy, but harmful pests need to be suppressed or eradicated in the areas where they can do harm, whether that's rats, mosquitoes, or locusts.