Rats can cause a huge amount of damages. They eat and contaminate food and animal feed. They also damage food and feed containers and packaging materials. Both Norway rat and roof rat will cause problems by gnawing on electrical wires and wooden building structures such as doors, ledges, corners even walls. Insulation within walls and ceilings can be torn up by rats for nesting.
Among the all the diseases that rats can transmit to humans or livestock are murine typhus, leptospirosis, salmonellosis (food poisoning), and ratbite fever. Plague is a well-known nasty disease that both roof and Norway rats can carry, but in some areas, it is more commonly associated with ground squirrels, chipmunks, and native woodrats.