Efficacy of selamectin, spinosad, and spinosad/milbemycin oxime against the KS1 Ctenocephalides felis flea strain infesting dogs

Table 1 Geometric mean flea counts and percent efficacy relative to nontreated controls for dogs treated with a selamectin topical spot-on, a spinosad/milbemycin oxime oral tablet or a spinosad only oral tablet

	Day 0		Day 7		Day 14		Day 21		Day 28
Treatment¹	Mean # of fleas^2,3	% control⁴	Mean # of fleas	% control	Mean # of fleas	% control	Mean # of fleas	% control	Mean # of fleas	% control
	24 hours post-treatment or infestation
Non-treated Control	26.38^a		46.39^a		35.99^a		28.85^a		51.46^a
Selamectin	10.45^a	60.4	0.12^b	99.7	1.52^b	95.8	0.62^b	97.9	3.62^b	93.0
Spinosad-Milbemycin	0.00^b	100.0	0.00^b	100.0	0.12^c	99.7	1.29^b,c	95.5	7.85^b	84.7
Spinosad	0.00^b	100.0	0.00^b	100.0	0.12^c	99.7	2.19^c	92.4	13.96^b	72.9
	48 hours post-treatment or infestation
Non-treated Control	36.25^a		38.71^a		24.40^a		33.81^a		30.81^a
Selamectin	3.10^b	91.4	0.00^b	100.0	0.12^b	99.5	0.12^b	99.6	1.33^b	95.7
Spinosad-Milbemycin	0.00^c	100.0	0.00^b	100.0	0.00^b	100	0.41^b	98.8	3.86^b,c	87.5
Spinosad	0.00^c	100.0	0.00^b	100.0	0.26^b	98.9	0.44^b	98.7	7.31^c	76.3

¹ Each of 6 dogs in the control group received no treatment. Each of 6 dogs in the Selamectin topical spot-on, Spinosad/Milbemycin oxime oral tablet or a Spinosad only oral tablet groups were administered the formulations according to label directions on Day 0.
² Each dog was infested with 100 adult Ctenocephalides felis from the KS1 strain on days -2, 7, 14, 21 & 28.
³ Geometric mean # of fleas recovered from dogs per treatment group.
⁴% control = ((geometric mean count control -geometric mean count treatment)/ geometric mean count control)) × 100.
^a,b,c geometric means within a column with unlike letter superscripts are significantly different (P <0.05).

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