Date of this Version
It was just over 10 years ago with the paper by Hadler and Shadbolt (1975) that a series of novel anticoagulants, which included brodifacoum, was announced. Today, after a decade of brodifacoum study and experience, the value of this compound in vertebrate pest management, particularly in rodent control, can scarcely be questioned. In order to most effectively build upon this experience, a thorough review of the literature for the period of 1975 to 1985 was undertaken to also include much unpublished information available to the authors. Undoubtedly to a greater extent than any other new vertebrate pesticide, brodifacoum has been the subject of extensive testing and development around the world. This research has included much original work by scientists within ICI since 1975 with the acquisition of rights to brodifacoum and related compounds, in the areas of efficacy, toxicity, hazard determinations, formulation development, and new application techniques. Supporting open, responsible research and publication in the scientific literature, ICI has provided brodifacoum samples to, and maintained close liaison with, various government, university, and other research groups in the United States, England, and elsewhere. These efforts and resulting publications in recognized journals and proceedings have served to stimulate, coordinate, and add to the rapidly growing body of scientific knowledge about this compound. Laboratory characterizations led to field trials, and the confidence and results derived from such testing allowed in due course for registrations of brodifacoum as a vertebrate toxicant in many countries. Then other but equally valuable data sets could emerge for documentation. These are concerned with the practical experience with a chemical tool in actual large-scale use. A number of conferences or symposia have also been convened or sponsored by ICI to supplement the few regular symposia on the subject, and to provide an open forum on vertebrate pest management, including discussions of brodifacoum research findings. Examples are an International Public Health Seminar, in Surrey, England, in 1979; a symposium entitled "The Organization and Practice of Vertebrate Pest Control," held in Hampshire, United Kingdom, in 1982 (Buckle 1983); and a conference, Rodent Control in the Tropics, held in London in 1983 (McDonald 1983). Proper concern and attention have been given by ICI and other researchers to determining environmental and nontarget animal impact of brodifacoum use (Kaukeinen, 1982, 1984b; Hegdal et al. 1984; Godfrey 1985). As with all available vertebrate pest toxicants, brodifacoum can be toxic to other organisms if misused or accidently ingested. Formulation developments and new application techniques, to be later discussed, can reduce hazard and improve selectivity by taking advantage of brodifacoum's unique properties. The discovery of brodifacoum in England as first published in 1975 (Hadler and Shadbolt) was quickly followed by reports concerning its characterization and promise in the area of rodent control. While initial reports concerning a "new development in rodent control" were concerned with difenacoum, a related compound in the Hadler series, published work on brodifacoum in England by Hadler and the staff of the UK Ministry of Agriculture, Fisheries and Food soon followed (Redfern et al. 1976, Rowe and Bradfield 1976, Anon. 1978). These studies characterized the properties of brodifacoum against those most predominant of rodent pests, the commensal species Rattus norvegicus, Rattus rattus, and Mus musculus. Research began soon after in the United States and elsewhere on these and other species. Such work, including further commensal studies from MAFF, such as Rowe et al. (1978), was the subject of an extensive review by Dubock and Kaukeinen (1978). That first major review of brodifacoum encompassed 25 species, involved work in 14 countries, and contained 38 references. Additional reviews or general articles that summarized brodifacoum's characteristics or that touched upon further findings soon followed (e.g., Hadler 1979, Dubock 1980, Anon. 1981b, Hone and Mulligan 1982, Renapurkar and Kamath 1982, Meehan 1984, Lund 1985); however, these were not comprehensive, prompting the current review. Prior reviews did indicate the basic properties of the compound, which are now generally familiar, and provided a framework for an update.