Evaluation of five systemic insecticide baits to control fleas (Siphonaptera: Pulicidae and Ceratophyllidae) on rodents (Rodentia: Muridae and Sciuridae)

Abstract

We evaluated the efficacy of 5 systemic insecticide compounds, each incorporated into edible baits to control flea (Siphonaptera) vectors of the plague bacterium Yersinia pestis (Lehmann and Neumann), with brown rats (Rattus norvegicus, Berkenhout) and rock squirrels (Otospermophilus variegatus, Erxleben) in a laboratory environment. Rodents were exposed to diets lacking or containing insecticides for 24 h at which point adult Ctenocephalides felis (Bouché), Xenopsylla cheopis (Rothschild), or Oropsylla montana (Baker) were applied to rodents. Fleas were monitored for survival 1 d later and subsequent time points to evaluate residual efficacy, with relative comparisons of survival rates for individual fleas applied to nontreated and treated hosts. With brown rats, cythioate was ineffective in suppressing fleas after 1 d; nitenpyram and selamectin were ineffective after 7 to 8 d. Imidacloprid suppressed C. felis survival on rats by 94% at day 1 but efficacy declined to 11% by day 8. Fipronil applied orally to rats suppressed the survival of C. felis and X. cheopis by 52% to 95% and 45% to 96% at days 1 and 7 to 8, respectively, and suppressed O. montana survival on rock squirrels by 70% to 94% from days 1 through 40. Results of this formative laboratory investigation sparked intensive field research on, and refinement of, fipronil baits for flea control, plague mitigation, wildlife conservation, and One Health objectives.