Dose determination of a novel formulation of metaflumizone plus amitraz for control of cat fleas (Ctenocephalides felis felis) and brown dog ticks (Rhipicephalus sanguineus) on dogs

A novel spot-on formulation containing metaflumizone and amitraz (ProMeris®/ProMeris Duo® for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated in a laboratory study to determine the appropriate dose for efficacy against fleas and ticks on dogs for 1 month. Thirty-six Beagles were randomly allocated to six equal groups and individually housed. One group remained nontreated. Another was treated with a placebo formulation (solvents with no active ingredients). Three groups of dogs were treated topically with the metaflumizone plus amitraz formulation (150 mg of each of metaflumizone and amitraz/ml), at volumes providing doses of 10, 20 and 40 mg each active/kg. The final group was treated with a commercial spot-on providing 6.7 mg fipronil/kg. All treatments were applied to the skin at a single spot between the scapulae on Day 0. Dogs were infested with 50 adult brown dog ticks (Rhipicephalus sanguineus) on each of Days −2, 5, 12, 19, 26, 33 and 40, and with 100 cat fleas (Ctenocephalides felis felis) on Days −1, 6, 13, 20, 27, 34 and 41. Dogs were examined and parasites “finger counted” on Day 1 to estimate knock down efficacy, and all animals were comb counted to determine the numbers of viable fleas and ticks on Days 7, 14, 21, 28, 35 and 42. There were no significant differences in parasite counts between the nontreated control and the placebo-treated control groups for either fleas or ticks (P > 0.05) except for very slight reductions on Day 7 for fleas and Day 14 for ticks, demonstrating that the formulation excipients had no activity. The qualitative finger counts on Day 1 indicated that all of the insecticidal treatments resulted in a noticeable reduction in flea and tick numbers within 1 day of treatment. All of the metaflumizone and amitraz treatments and fipronil resulted in significantly lower flea and tick numbers relative to nontreated controls on all posttreatment count days (P < 0.05). For the metaflumizone plus amitraz treatments, mean flea and tick counts for the 10 mg/kg dose were significantly higher than those for the 20 mg/kg dose (P < 0.05) from Day 21 on. There was no significant advantage provided by the 40 mg/kg dose over the 20 mg dose throughout the entire study (P > 0.05). The two higher metaflumizone plus amitraz doses provided >95% control of fleas and >90% control of ticks for at least 35 days after treatment, and this level of control was similar to that of the commercial fipronil product. The 20 mg/kg dose was selected as the minimum commercial dose rate to provide effective flea and tick control for at least 1 month following a single treatment.