Against this background of rodent problems, commendable efforts have been seen in the development of more effective and more practical rodent control methods. While trapping rodents has been practiced for about 5,000 years, modern traps are easier to set and some feature a multiple catch capability. Other non-chemical methods of rodent control include public health education, physical exclusion of rodents, and sanitation measures, all of which are aimed at denying rodents food and shelter, measures that should form a primary part of any rodent control program. Unfortunately, non-chemical methods are timeconsuming, may not always be practical or affordable, and used alone may not achieve acceptable results. For these reasons, the use of rodenticides plays a vital role in most integrated rodent management programs.
Rodenticide use is not a new approach. Aristotle reported the use of strychnine for rodent control in 350 B.C. For the next 23 centuries, until 1950, the various rodenticides which were used could all be described as acute or single exposure toxicants. They included botanical extracts (e.g. red squill and strychnine), inorganic chemicals (e.g. arsenic, phosphorus and thallium sulfate) and, in the 20th century, various synthetic organic chemicals (e.g. ANTU, DDT and sodium fluoroacetate). In addition to the aforementioned chemicals which were used to make rodenticide baits, various fumigants, including hydrogen cyanide and carbon bisulfide, were used for many decades prior to 1945 .
Acute rodenticide baits and fumigants have the advantage of potentially producing a fast kill of rodents, sometimes within a few minutes. However, in the case of baits, the rodents often relate eating the bait to the onset of poisoning symptoms. This results in some rodents ceasing bait consumption before they have taken a lethal dose and, thereafter, becoming “bait shy” and virtually impossible to control with the same bait. Another important disadvantage of the acute rodenticides is that they are nearly all highly toxic to non-target species, including people, a drawback made worse by the absence of specific antidotes. The addition of bittering agents and emetics to some acute baits offers added protection since rats and mice cannot vomit. However, the addition of emetics (to induce nausea and vomiting) or substances like Bitrex®, denatonium benzoate, which deter non-target species also reduce palatability of the bait to rodents.