Effectiveness and residual speed of flea kill of a novel spot on formulation of spinetoram (Cheristin) for cats.

Abstract

BACKGROUND: A spot-on spinetoram formulation (Cheristin) was developed to eliminate fleas from infested cats. This paper describes three spinetoram studies: two for registration (Studies 1 and 2), and one comparing residual speed of kill (SOK) with topically applied fipronil/(S)-methoprene (FSM) and imidacloprid (Study 3). METHODS: Cats were randomized to treatment based on flea counts from infestations placed within 2&#xa0;weeks prior to treatment. In Studies 1 and 2, groups were untreated control and spinetoram; in Study 3, groups were untreated control, spinetoram, FSM and imidacloprid, all applied per label on Day 0. Cats were infested the day before treatment. In Studies 1 and 2, counts were completed 48&#xa0;h post-treatment and after weekly challenges through 5&#xa0;weeks. In Study 3, infestations were completed weekly through Day 28, with counts 1, 4, 8 and 12&#xa0;h after treatment or post-infestation (PI). Efficacy was determined on geometric mean flea count reductions compared with controls, and in Study 3 mean flea counts in spinetoram-groups were compared with those in FSM and imidacloprid groups. RESULTS: In Studies 1 and 2, spinetoram effectiveness was 100% against existing infestations, and at least 96% through Day 37. In Study 3 mean counts were not significantly different from controls in any group until 8&#xa0;h post-treatment when imidacloprid counts were significantly lower than spinetoram counts, which were in turn significantly lower than FSM counts (P&#x2009;<&#x2009;0.05). At 1&#xa0;h PI spinetoram-group counts were significantly lower (P&#x2009;<&#x2009;0.05) than counts in: controls, all days; imidacloprid, Days 7, 14, and 28; FSM, Days 14 and 28. At 4&#xa0;h PI, spinetoram mean counts were significantly lower (P&#x2009;<&#x2009;0.05) relative to: controls, all days; imidacloprid, Days 7, 14 and 21; FSM, Days 7, 14, 21 and 28 (P&#x2009;<&#x2009;0.05). On multiple occasions, at 8 and 12&#xa0;h PI, mean counts were significantly lower (P&#x2009;<&#x2009;0.05) for spinetoram than for imidacloprid and FSM; at no point were FSM or imidacloprid significantly more effective than spinetoram against new infestations. All treatments were well tolerated. CONCLUSIONS: Spinetoram was highly effective for at least 1&#xa0;month post-treatment and provided more rapid month-long residual SOK than FSM or imidacloprid.