title: Speed of flea knockdown of spinosad compared to afoxolaner, and of spinosad through 28 days post-treatment in controlled laboratory studies.
abstract: BACKGROUND
  The speed of flea knockdown by different products and their duration of effectiveness are factors which affect veterinarian prescribing decisions. To further validate the month-long pulicidal effectiveness of spinosad and determine its rate of flea knockdown to that of afoxolaner, three studies were conducted in two laboratories in the United States, utilizing flea infestations from colonies which are regularly refreshed through introduction of locally caught fleas.
  
  
  METHODS
  All study assessors were blinded, dogs were ranked by pre-study flea counts and randomized accordingly, and treatments administered on Day 0. All studies included a negative control group; two also included an afoxolaner group. In one study, flea challenges for treated and control dogs (10 per group) were completed 21 and 28 days after treatment and counts were performed 24 h later. In each of two speed-of-knockdown (SOK) studies, 36 dogs were randomized, six dogs per group, to: untreated controls; administered oral afoxolaner (2.6-6.2 mg/kg); or oral spinosad (32.1-59.2 mg/kg). In the SOK studies, live fleas from Day -1 infestations were counted after being combed off at 1 and 3 h after treatment, and after reinfestations on Day 7.
  
  
  RESULTS
  There were no treatment-related adverse events. Spinosad was 98.6% effective at 28 days post treatment. For SOK, geometric mean live flea counts for afoxolaner were not different from controls at any assessment. For spinosad, all mean counts were significantly lower than in controls (p ≤ 0.0128) except at 1 h post treatment in both studies. Spinosad was significantly more effective than afoxolaner in both studies at 3 h post treatment (p ≤ 0.0065) and post-Day 7 infestation (p ≤ 0.0054), and at 1 h post treatment (p = 0.0276) and post-Day 7 infestation in one study.
  
  
  CONCLUSIONS
  These data validate spinosad's faster onset of flea knockdown than afoxolaner against infestations present at the time of treatment, and faster residual speed of flea knockdown for at least 7 days post treatment, and confirm spinosad's extended residual speed of kill for at least 28 days post treatment.
authors.affiliation: Elanco Animal Health, Greenfield, IN, USA. snyder_daniel_e@elanco.com.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Snyder
authors.affiliation: Elanco Animal Health, Greenfield, IN, USA. rumschlag_anthony_j@elanco.com.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Rumschlag
authors.affiliation: Elanco Animal Health, Greenfield, IN, USA. young_lisa_marie@elanco.com.
authors.forename: Lisa Marie
authors.initials: LM
authors.lastname: Young
authors.affiliation: Ryan Mitchell Associates LLC, Westfield, NJ, USA. wgr@ryanmitch.com.
authors.forename: William G
authors.initials: WG
authors.lastname: Ryan
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D004338:Drug Combinations; D064420:Drug-Related Side Effects and Adverse Reactions; D058267:Flea Infestations / Q000188:drug therapy*; D007306:Insecticides / Q000008:administration & dosage* / Q000009:adverse effects / Q000494:pharmacology; D007555:Isoxazoles / Q000008:administration & dosage* / Q000009:adverse effects / Q000494:pharmacology; D018942:Macrolides / Q000008:administration & dosage* / Q000009:adverse effects / Q000494:pharmacology; D009281:Naphthalenes / Q000008:administration & dosage* / Q000009:adverse effects / Q000494:pharmacology; D005423:Siphonaptera / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors; D014481:United States
chemical_list: D004338:Drug Combinations; D007306:Insecticides; D007555:Isoxazoles; D018942:Macrolides; D009281:Naphthalenes; C000589002:afoxolaner; C415329:spinosad