Our neighbours to the south, Seattle, are the No. 1 city in the U.S. for a rats problem. Killing rats is the only way to rid the city of its rats epidemic. A rat sighting is the only evidence needed to indicate a nest is near. Rats are social rodents and they live in groups. They are incessantly breeders, with each mating couple producing as many as 900 offspring in a single year. Coming into contact with rat droppings, mucous, or urine in dust particles is enough to contract over 10 fatal diseases which kill millions of people every year. These diseases are spread by fleas and ticks feeding on rats. When rats aren’t feeding, making nests, mating or feeding, they are gnawing. Because their teeth never stop growing, they instinctively gnaw every day to keep them trimmed; such as electrical wiring.
https://www.linkedin.com/pulse/hey-seattle-1-rats-randy-bilesky?published=t