Generally, there are three species of common house rodents on the American mainland. Additional species occur in other areas of the world. The most important rodents from the medical and uxmomic viewpoint are the Norway or brown rat, the black roof rat, and the house mouse.
Rodent control programs should include elimination of food and shelter, rodent-proofing of structures, and active destruction of rodents by poisoning and trapping. Mice should be controlled by systemic trapping rather than poisoning because they nest indoors and will die in wall voids, etc., causing odor problems.
Poisoning should be regarded as supplementary to environmental sanitation and trapping; it becomes the method of choice (except for mice) once rodents are under control. Poisoning of rodents found aboard ships is not recommended due to odor problems; therefore, trapping is the method of choice when afloat. Proper sanitation, including garbage disposal, rat poisoning, harborage elimination, and food storage are of utmost importance in the permanent control of domestic rats and mice. Food storage structures should be completely rat-proofed. Stockpile supplies on elevatml platforms so that no concealed spaces exist. Garbage should be put in tightly covered cans that should be placed on concrete slabs or platforms. Surrounding areas should be carefully policed and garbage removed frequently. Open garbage dumps should not be tolerated.
When structures are built, all openings should be covered with 28-gauge, 3/8-inch (9.53 mm) mesh, galvanized hardware cloth; doors should be self-closing and tight-fitting, and those giving access to galleys and food-storage rooms should be equipped with metal flashing along the base. Walls and foundations should be of solid construction.
One of the most popular methods of killing rats is by the use of poisons. Resistance by rats and mice to the older anticoagulants, particularly warfarin, is well-documented in parts of Europe and the United States (contact the area DVECC or EPMU for advice), but where they. are still effective they remain the method of choice. Rat poisons may be used alone or with water or food bait. The two most common species of rats have somewhat different food habits. Norway rats are more inclined to be meat and fish eaters; roof rats often prefer fruits and vegetables.
Anticoagulant rodenticides prevent blood clotting and cause capillary damage, leading in most cases to internal hemorrhage and death. At concentrations recommended for rodent control, anticoagulant agents are not detectable or objectionable to rodents; but for effective control using warfarin based anticoagulants, they must be ingested several times. These feedings need not be on consecutive days but should occur within a 10 to 14-days interval. Adequate ex- posure to anticoagulant baits is contingent on the establishment of a sufficient number of protected bait traps. This can be accomplished by the use of properly constructed bait boxes. Baits can be protected by improvised means with locally available materials. Every container of poisoned bait must be labeled POISON with red paint in English and in the local language in non-English speaking areas. Bait stations should be inspected and replenished with fresh bait at weekly intervals.
Where rodent infestations occur, the use of poisoned bait, poisoned water, and traps, including glue boards, is recommended to obtain quick initial control. When traps are no longer useful, they should be removed but the baiting continued. This is appropriate especially in buildings where food is stored, prepared, or served, unless it is determined that the building is not vulnerable to reinfestation. In tropical and semitropical areas where rodent infestation is commonplace and not confined to buildings, area as well as building control must be used.
Premixed anticoagulant baits containing a rolled oat food base are obtainable from standard stock. If the food offered is not readily acceptable to the target rodent population, it may be necessary to test bait with additional food items. Cereal baits can be made more acceptable to rats by adding edible oil, peanut butter, and sugar. Test bait samples should be selected from three classes of foods known to be suitable bait. They include cereals (cornmeal, bread, mash, etc.) and fruits and vegetables (melons, bananas, sweet potatoes, etc.). It is important to use freshly prepared baits because rodents will reject stale or spoiled food.
Rat infestation in areas where water is scarce may often be controlled by using poisoned water. A water-soluble anticoagulant rodenticide is available from standard stock. Label instructions should be followed when using this item.
Rodenticide, Bait, Anticoagulant, FSN 6840-00-753-4973, is a ready-to-use type containing an anticoagulant chemical, rolled oats, and red dye, sugar, and mineral oil.
This item is used directly from the container without further mixing. The single dose rodenticides zinc phosphide and Maki, although surpassed in safety by