Pest rodents damage agricultural crops,stored foods and infrastructure and are significant carriers of diseases transmitted to humans.We have assessed the efficacy of a combined rodenticide-insecticide that kills rodent ectoparasites (potential disease vectors) prior to the death of the rodent.Such a product could reduce the risk of disease transmission where rodent baiting is carried out in close proximity to people or companion animals.Using 2 model systems,one based on Norway rats (Rattus norvegicus) and ticks/fleas and the other on laboratory mice (Mus domesticus) and ticks/fleas,we assessed three potential insecticides delivered in extruded pellets for their impacts on palatability and their efficacy if delivered orally.Success with these experiments resulted in the testing of the efficacy of one insecticide,Fipronil,in combination with one rodenticide (brodifacoum) for both mice and rats with ticks and fleas.Animals were exposed to the test product or control product for 3 days.All treated rats and mice died within 4-9 days after first exposure to the combined product and >90%of added insects (whether ticks or fleas) which attached to treated rodents died on or before the death of the host.Similar results were obtained for ticks and fleas and laboratory mice.The three criteria that were established to define acceptance of the product were met: >90%mortality of mice and rats within 14 days; >90%mortality of attached ticks and fleas before host death; and >90%mortality of insects that attached after the rodent had been exposed to the product.