Recent developments in anticoagulant rodenticide resistance studies: Surveillance and application in the United States

Since anticoagulant rodenticide resistance was first discovered in the United States in 1971, it has become apparent that the phenomenon is widespread. In cooperation with the Center for Disease Control, a nationwide surveillance program was initiated in 1977 to obtain statistically valid samples of rats from federally funded projects of the Urban Rat Control Program. A summary is given of the basic sampling, testing, and analysis components of this study. Problems encountered in all aspects of the first three years of the program are discussed along with results from the 40 completed samples. The 16 cities with significant Anticoagulant Resistance Problem Areas are distinguished from those in which resistance has merely been observed. Levels of resistance in various rat populations are discussed and recommendations are made in support of integrated pest management programs. Recent findings from retesting resistant rats, half of which die, are presented with regard to application of the surveillance program