Rats are dangerous to humans because they can carry serious diseases. They also carry ticks, fleas, and lice, which carry their own diseases and can bite humans and pets. Both rats and mice leave unsanitary droppings everywhere.
Rodents are chewers. They need to chew to keep their teeth a manageable length. If they can’t chew, their teeth grow too long and they starve. They’ll chew through most anything in a bid to get where they want to go, mainly to get to the food. They’ve even been known to chew through household wiring in order to clear a path to a room where food is stored.
Diligence is the best first defense against rodents. Pet food and water bowls should be taken up at night, food should be stored in glass or metal containers where rodents are a problem. Sinks and counters should be free of dirty dishes overnight and there should be no standing food or water.