The most important pest rat in the United States is the Norway rat, also called the brown rat, house rat, and sewer rat. Rats are responsible for the spread of many diseases including plague, typhus fever, rat-bite fever, leptospirosis, and Salmonella food poisoning. Sometimes rats transmit disease directly, by contaminating food with their urine or feces, or from their bite. Sometimes they transmit disease indirectly via fleas. Rats have never been found to be infected with rabies, and there are no documented cases of rabies transmission from rats to humans.
The Norway rat has a heavy, thick body, small ears, and a blunt nose. Its tail is shorter than the combined length of its head and body. The body of the adult Norway rat is about nine inches in length. The combined length of its body and tail is about seventeen inches. Its fur is medium brown in color. Rats have small ears in proportion to their body size.
A mature female rat can give birth to about twenty young in a year. There is 4 to 6 young per litter. They are hairless, and their eyes are closed when they are born. Within two weeks their eyes are open, they become furry and begin exploring. The young are weaned at 4 or 5 weeks, and at three months they are independent of the mother. They will then mate, and continue the cycle. The average lifespan of a rat in nature is less than one year.
Rats are social and live in colonies. They mark their territories with urine and glandular secretions. Rats have poor vision and are nearly color blind, but their eyes are adapted to low light. The limit of their vision is thirty to forty-five feet. Rats have an acute sense of smell, taste, and touch. Rats are wary of anything new in their territory, which makes trapping and baiting difficult.
Rats need about one ounce of food per day. Norway rats eat a variety of foods including meat, fish, insects, nuts, grain, pet food, and garbage. Rats usually begin foraging after dark, mostly between dusk and midnight, but short bursts of activity can occur anytime. Rats will travel 100 to 150 feet from their nest looking for food and water.
A single rat can produce fifty droppings per day. Large numbers of droppings can be found in areas where they nest and feed. Salmonella bacteria thrive in the intestinal tracts of rats. When rats travel to food preparation areas, and food storage areas their droppings can transmit Salmonella food poisoning to people.
The key to controlling rat populations is the elimination or restriction of the rat’s food supply. This can be best achieved by the application of good sanitary practices, especially in regard to the proper handling and disposal of garbage. Garbage should not be left exposed for a longer time than necessary to deposit the garbage in proper waste containers. Garbage should be placed in proper waste containers with lids that can be sealed tight, and garbage should be disposed of properly at least once a week.
Public Health regulates the handling and disposal of garbage under Public Health Nuisance Regulation 2-93, Section 5. Public Health regulates rat infestations only within rental properties under Public Health Nuisance Regulation 2-93, Section 7D. In cases where rats have inhabited a rental property, Clermont County Public Health can order the property owner to initiate control measures within the structure. Public Health does not regulate rat harborage or rat populations in the outdoor environment.