Rats are ferocious, omnivorous and adaptable to all climates. Their high adaptability to changing environments and high reproductive rate have allowed them to advance side by side with man. Rats live and thrive under a wide variety of climates and conditions; they are often found in and around homes and other buildings, farms, gardens, and open fields.

Medical Importance

Rats and mice are carriers of a substantial number of diseases of man and livestock. The causative organisms of these zoonotic diseases may be viral, rickettsial, bacterial, protozoan, helminthic or trematodan. Many such pathogenic organisms are carried in the rats’ blood and therefore need an arthropod vector to act as intermediary in the transmission of the diseases to man. The transmission and spread of a whole range of common diseases including leptospirosis and salmonellosis are on the rise. New medical evidence and advance in biomedical techniques are starting to show that our relationship with rodents and the diseases they carry is much more intimate than anyone had suspected. Most of these diseases, such as hantavirus, leptospirosis, etc are mostly unrecognized because infected people frequently recover without realizing it. But if symptoms do not clear up the resulting illness are often severe or fatal.

Biology & Life Cycle

Rats, like house mice, are mostly active at night. They have poor eyesight, but they make up for this with their keen senses of hearing, smell, taste, and touch. Rats constantly explore and learn about their environment, memorizing the locations of pathways, obstacles, food and water, shelter, and other elements in their domain. They quickly detect and tend to avoid new objects placed into a familiar environment. Thus, objects such as traps and baits often are avoided for several days or more following their initial placement. The female comes into oestrus, attracts a male by smell and then mating takes place. Under normal conditions, the female will conceive and carry her young for 20 – 23 days. The pups are born blind and hairless. After 7 – 10 days, the young are fully haired and their eyes open, but they are still dependent on their mother for milk. They can be weaned as young as 20 days. Rats become sexually mature in 2 or 3 months. Under optimal conditions, they can give birth to 10 – 12 pups at a time and they can have as many as 10 litters of youngs per year. Rats of either species, especially young rats, can squeeze beneath a door with only a 1/2-inch gap. If the door is made of wood, the rat may gnaw to enlarge the gap, but this may not be necessary.


The most effective way to control rodents is to change the environment to make it less favourable for them. Three elements are necessary for a successful rat management program: sanitation measures, building construction and rodent proofing, and, if necessary, population control. Sanitation is fundamental to rat control and must be continuous. If sanitation measures are not properly maintained, the benefits of other measures will be lost, and rats will quickly return. Garbage, trash, and garden debris should be collected frequently, and all garbage receptacles should have tight-fitting covers. Where dogs are kept and fed outdoors, rats may become a problem if there is a ready supply of dog food. Feed your pet only the amount of food it will eat at a feeding, and store pet food in rodent-proof containers. The most successful and long lasting form of rat control in buildings is to “build them out.” Seal cracks and openings in building foundations, and any openings for water pipes, electric wires, sewer pipes, drain spouts, and vents. No hole larger than 1/4 inch should be left unsealed to exclude both rats and house mice. Make sure doors, windows, and screens fit tightly. Their edges can be covered with sheet metal if gnawing is a problem. When food, water, and shelter are available, rat populations can reproduce and grow quickly. While the most permanent form of control is to limit food, water, shelter, and access to buildings, direct population control is often necessary. For controlling rats indoors, use traps. Baiting is best done outdoors only, otherwise rats may die behind a wall. In hot weather, the stench of a dead rat can be unbearable and may necessitate cutting a hole in the wall to remove the carcass. Also, ectoparasites such as fleas and mites often leave dead rat carcasses and may infest the entire house if the carcass is not removed promptly.