The objective of the study was to evaluate the efficacy of ProMeris Duo® compared to Frontline® Spot-On Dog and an untreated control against lice (Trichodectes canis) infestations in dogs.

Twenty four animals with a lice burden of at least 10 were randomised into three groups of eight based on pre-treatment lice counts. Group 1 received no treatment and served as the untreated control group; Group 2 animals were treated with Frontline Spot-on Dog (CP) at the minimum recommended rate of 0.067 ml/kg bodyweight, once on Day 0; and Group 3 animals were treated with ProMeris Duo (IVP) at the minimum recommended dose rate of 0.133 ml/kg bodyweight, once on Day 0. Both the CP and IVP were applied as a single spot on the skin of the dog between the shoulder blades, except in two animals in the IVP group where the site of spot-on application had signs of skin infection: in each case the animal was dosed on the cranial side of the lesion along the dorsal midline.

Lice counts (the total number of lice counted in eight locations) were conducted on Days -7 and -1 prior to treatment and on Days 2, 7, 14, 21, 28 and 35 post-treatment. Efficacy was assessed based on a comparison of the geometric mean lice counts in the CP and IVP groups with that of the untreated control group at each time point.

Lice counts decreased to zero in two of the eight untreated control animals over the course of the study, but there were at least six infested animals at each time point. The percentage efficacy of ProMeris Duo on Days 2, 7, 14, 21, 28 and 35, respectively was 70.5, 97.3, 100, 100, 100 and 100. The corresponding figures for the CP were 87.9, 100, 100, 100, 99.7 and 100. At all post-treatment time points, animals treated with the CP or IVP had significantly (P<0.05) fewer lice than the untreated controls; however, there were no significant differences between the CP and IVP groups.

Both products effectively controlled lice infestation on dogs after treatment and were well tolerated during the course of the study.