Veterinarians and pet owners should expect that when correctly applied indoxacarb spot-on will control the existing flea burden on a cat and that there should be a rapid reduction in egg production from the existing flea infestation. Within 48 hours of application egg production was almost completely halted (98.9% reduction). Since none of those eggs produced adult fleas no dissemination of viable eggs occurred from treated cats within 2 days of treatment.
Most currently available residual topical spot-on and systemic insecticide formulations are marketed to provide at least 30 days of effective flea control. Indoxacarb spot-on certainly provided and exceeded that level of control. A single application of indoxacarb provided ≥99.6% control of adult cat fleas on cats for at least 45 days after treatment.
Following treatment, egg production from weekly flea reinfestations was reduced by ≥99.9% at least 5 weeks. Consumption of blood is necessary before cat fleas can initiate reproduction and egg production does not begin until 24–48 hours after females take their first blood meal [1, 2]. Therefore, if a residual insecticide can kill or produce toxicity in newly acquired fleas within 24 hours, egg production should be markedly reduced or halted. While this study did not evaluate the residual speed of kill of indoxacarb or reduction of blood consumption by adult fleas, it did demonstrate that indoxacarb had a profound effect upon egg production. This indirectly indicates that indoxacarb is rapidly toxic to fleas and thus markedly reduces blood feeding by fleas.
Indoxacarb also had an effect upon adult flea emergence from eggs. While this study did not evaluate egg hatch directly it is anticipated that the effect of indoxacarb was on egg viability. Eggs collected from trays under treated cats were sorted and removed from all debris from those cats. The eggs were subsequently placed into standard rearing media. Following this procedure any larvae hatching from those eggs would have had no further contact with indoxacarb. Similar marked lethal effect on egg viability by a flea adulticide has been previously observed with selamectin .
Effective residual flea adulticides should have sufficient residual activity to provide for continuing kill of most if not all the newly emerging fleas that jump onto the treated pet between applications. If a flea product also has an effect upon the viability of the eggs produced by any female flea surviving the adulticidal effect, that product would markedly suppress the reproductive success of a flea population [6, 7]. In this study indoxacarb demonstrated marked flea kill, profound reduction in egg production and apparent ovicidal activity, as has been observed in other insect species . This combination of attributes provided ≥99.9% reduction in reproductive success (predicted emergence) for 5 weeks following a single application of indoxacarb. Proper application of indoxacarb to cats in a flea infested home should effectively drive the flea population to extinction.
This study was conducted using the KS1 flea strain. Several previous studies have demonstrated that this strain has reduced susceptibility or outright resistance to carbaryl, chlorpyriphos, fenthion, fipronil, imidacloprid, permethrin, pyrethrins, and spinosad [3, 19–24]. This study showed that indoxacarb performed well against this KS-1 flea strain.