A field trial of spinosad for the treatment and prevention of flea infestation in shepherd dogs living in close proximity to flea-infested sheep

Abstract

BackgroundThree flea species, Pulex irritans, Ctenocephalides canis and C. felis parasitize shepherd dogs living on sheep farms in Greece. The aim of this randomized, blinded, placebo-controlled trial was to examine the efficacy of spinosad, when administered three times every 4 weeks, as the only intervention to treat and prevent flea infestations in shepherd dogs living on sheep farms.MethodsThirty dogs living on sheep farms and infested by at least 24 fleas were randomly allocated into equal groups. Group A dogs received spinosad (45–70 mg/kg body weight), every 4 weeks for three administrations, whereas Group B dogs were placebo-treated. Flea counting was performed at the beginning of the trial (day 0) and after 14, 28, 56 and 84 days. The first five fleas from each dog and 2–6 fleas collected from 5–11 sheep were used for species identification.ResultsThe percentage of dogs with zero flea counts was significantly higher in group A than in group B at days 14, 28, 56 and 84 and flea counts were significantly lower in group A than in group B at days 14, 28, 56 and 84. In group A, flea counts were significantly lower at days 14, 28, 56 and 84 compared to day 0 whereas there were no changes in flea counts of group B dogs. The percent efficacy of spinosad for the treatment and prevention of flea infestation was higher than 98 % (arithmetic means) or higher than 99 % (geometric means) throughout the study. No adverse reactions were recorded.C. canis was the predominant flea species of dogs at day 0. In group A the relative abundance of C. felis increased at day14 whereas in group B the relative abundance of P. irritans increased at days 14, 28, 56 and 84.ConclusionsSpinosad is safe and effective for the treatment of C. canis and C. felis infestations and for the prevention of P. irritans, C. canis and C. felis infestations in shepherd dogs living in close proximity to sheep.

A field trial of a fixed combination of permethrin and fipronil (Effitix®) for the treatment and prevention of flea infestation in dogs living with sheep

“…Approximately one year earlier (from April to July 2014), we had conducted a similarly-designed randomized, blinded, placebo-controlled trial of 3 month-duration, to examine the efficacy of spinosad (Comfortis ® ; Elanco Animal Health) for the treatment and prevention of flea infestation in dogs living with sheep [ 7 ]. In that study, the geometric-mean based efficacy of spinosad ranged from 99.4 to 100%, the arithmetic-mean based efficacy ranged from 98.7 to 100% and the percentage of dogs with zero flea counts ranged from 80 to 100%.…”

“…Although dogs were infested by the same two flea species on day 0, the relative abundance of C. canis was numerically lower in the present (88.6%) compared to the previous study. Also, P. irritans infestation was not witnessed in the present study whereas it was the predominant flea species on placebo-treated dogs from day 14 until the end (day 84) of the previous study; (iii) in the present study, flea combing was continued until no fleas could be recovered for the last 5 min whereas in the previous study it was continued until no fleas could be recovered for 1 min; (iv) due to its systemic mode of action, the efficacy of spinosad is not expected to be negatively influenced by environmental factors, such as exposure to rain; (v) passive transfer of spinosad from treated to control dogs is not expected to occur; and (vi) in the present study flea combing was performed in the premises whereas in the previous study dogs were separated from the sheep and removed from the heavily-infested area for at least 4 h before flea counting, thus minimizing the chances of newly-acquired flea infestations [ 7 ].…”

“…Worldwide, Ctenocephalides felis is the most common flea species parasitizing dogs [ 2 ], but in Greece C. canis was more prevalent among dogs admitted to a University Teaching Hospital [ 5 ]. In addition, when dogs living in Greece on sheep and/or dairy goat farms were examined, the most common flea species found were C. canis and Pulex irritans , followed by C. felis [ 6 , 7 ]. In previous studies, all dogs living with sheep had a high flea burden (median: 48 fleas per dog), the same was true for some of the sheep [ 7 ] and signs of severe flea infestation were witnessed in the people in contact with these dogs [ 6 ].…”

Speed of flea knockdown of spinosad compared to afoxolaner, and of spinosad through 28 days post-treatment in controlled laboratory studies

“…Moreover, the concept of spinosad variability arising from laboratory studies conflicts with the consistency spinosad has shown in field studies. In fact, spinosad appears to be unique among flea control products in showing >99 % effectiveness in a number of separate multi-clinic studies across Europe and the United States in which the product was administered monthly by dog owners [ 5 – 10 ].…”

“…With 100 % effectiveness reported within 4 h of treatment of existing infestations, spinosad was shown to have a comparable onset of activity to nitenpyram, but also provided a duration of flea knockdown that reduced flea egg output over one month by >99.8 % [ 4 ]. Controlled field studies with spinosad reported from 2007 through 2015 have confirmed its ongoing and consistent efficacy in field studies, achieving a high level of flea control in households that included treated dogs and cats, and alleviating the clinical signs of flea infestation, including pruritus [ 5 – 10 ].…”