Four laboratory studies were conducted to demonstrate that a single topical dose of a
novel spot-on combination containing fipronil, amitraz and (S)-methoprene (CERTIFECTTM,
Merial Limited, GA, USA) is efficacious against the brown dog tick, Rhipicephalus sanguineus.
In each study, 6–8 male and 6–8 female purpose-bred, laboratory mongrels, terrier cross
or Beagles were randomly assigned to one of two study groups (treated and untreated),
based on pre-treatment parasite counts. Starting on the day before treatment, each dog
was infested weekly with 50 ticks. Ticks were thumb counted at various time points after
treatment and weekly infestations starting as early as 6 h and continued at 12, 18 and
24 h depending on the study. Ticks were removed and counted at 48 h after treatment and
weekly infestations. CERTIFECT provided rapid and excellent control of pre-existing and
newly acquired infestations of R. sanguineus with efficacy as high as 93% within the first
12 h after a single topical treatment. Excellent control (>96%) of R. sanguineus as early as
18 h, following post treatment infestations was maintained for at least 35 days.