Evaluation of hair loss in cats occurring after treatment with a topical flea control product.

BACKGROUND: A formulation containing 39.6% spinetoram resulted in a higher than anticipated number of reports of alopecia at the site of application in the first months following commercial product launch. HYPOTHESIS/OBJECTIVES: To determine the cause of the alopecia using histopathology, including assessment for inflammation, follicular findings of physical trauma (plucking/pulling behaviour) and changes in follicular cycling. ANIMALS: Twenty-four flea-free, male and female adult domestic short hair cats within a private research colony. METHODS: Cats were treated with a single application of 39.6% spinetoram on day 0; personnel were not blinded. Observations of the skin and hair coat began immediately and were repeated at 30 min and 1, 2, 3, 4, 6, 8 and 12 h post-application and then on subsequent days at the same time as initial dosing and at 2, 4, 6, 8 and 12 h after that time, until day 5. If hair thinning or loss was observed, a skin biopsy sample was collected. Two cats not exhibiting abnormalities were biopsied on day 6. RESULTS: Thirty-eight per cent of cats (nine of 24) developed hair thinning and alopecia of sufficient severity within 78 h post-application of the product to warrant skin biopsy. Abnormalities in the skin were limited to the application site and were consistent with physical trauma (pulling or plucking) to the hair. CONCLUSIONS AND CLINICAL IMPORTANCE: Microscopic changes in the hair follicles of affected cats were consistent with self-induced trauma or barbering behaviour. All changes were reversible and paralleled findings associated with well-established, topical flea control products.

Effects of orally administered spinosad (Comfortis) in dogs on adult and immature stages of the cat flea (Ctenocephalides felis).

The efficacy of spinosad against adult fleas (Ctenocephalides felis) on dogs was evaluated in three controlled, blinded studies. One study was conducted to determine speed of kill on experimentally infested dogs. Two additional studies were designed to assess the efficacy of spinosad in preventing environmental contamination with flea eggs (USA study and EU study). An additional objective of the USA study was to assess the effects of skin and hair-coat debris from spinosad-treated dogs on eggs and larvae of C. felis. Dogs were randomly allocated to treatment with beef-flavored spinosad tablets, administered orally at a minimum dosage of 30mg/kg, or placebo. In the first study, speed of kill was determined by flea comb counts performed at 0.5, 1, 2, 4, 8, 12, 24 and 48h after spinosad treatment. Reductions in geometric mean flea counts for spinosad-treated dogs, compared to placebo were 53.7% at 0.5h, 64.2% at 1h, 85.8% at 2h and 100% at 4 through 48h post-treatment (p<0.05 at 1h and beyond). In the 2 flea egg production studies, dogs were treated (spinosad or placebo) once on day 0, infested with 600 fleas approximately 3h post-treatment and reinfested with approximately 600 fleas at intervals over 1 month. Flea eggs were collected starting at approximately 72h after each infestation. Eggs were examined for any effects of spinosad on egg viability. Efficacy of spinosad was also evaluated against environmental eggs and larvae exposed to canine hair-coat debris collected on days 3, 7, 14, 21, and 30. Spinosad was highly effective in reducing flea egg production (>99.8% across the entire study period) compared to control dogs in both egg collection studies. Insufficient numbers of eggs were recovered from spinosad-treated dogs to determine the viability of those eggs. There was no evidence of any effect on environmental flea stages, indicating that spinosad was not present in the skin debris of spinosad-treated dogs. The capability of spinosad to quickly kill adult fleas, and to greatly reduce egg production following challenge with high numbers of adult fleas is important in breaking the flea life cycle and preventing the introduction and establishment of new flea infestations in the household.

Knockdown and mortality comparisons among spinosad-, imidacloprid-, and methomyl-containing baits against susceptible Musca domestica (Diptera: Muscidae) under laboratory conditions.

The activity of spinosad, imidacloprid, and methomyl baits and technical actives were assessed against susceptible house flies, Musca domestica L. (Diptera: Muscidae). In a feeding assay, imidacloprid affected flies more rapidly than methomyl or spinosad, but spinosad was 2.7 times more potent than methomyl and 8 times more potent than imidacloprid. The profile of technical actives correlated with their respective fly bait formulations in laboratory assays. Although having the most rapid onset of activity in laboratory tests, up to 50% of flies remained alive after exposure to imidacloprid bait. In contrast, <5% of flies survived 24-h exposure to spinosad or methomyl baits. High temperature reduced the knockdown activity of imidacloprid bait and slowed the speed of kill for spinosad and methomyl baits over a 24-h exposure period. Spinosad and methomyl baits were also superior to imidacloprid when applied to the floors of environmentally controlled rooms at label recommended rates, providing good fly control for up to 21 d. The fact that a significant percentage of flies exposed to imidacloprid were rapidly knocked down but subsequently remained alive in all of the assays suggested that flies were recovering from initial exposure to this compound. Given its favorable safety profile, a high degree of initial and residual activity comparable with methomyl and lack of cross-resistance to other chemistries, spinosad bait may be a valuable component of house fly control programs to help control or delay the emergence of resistant populations.

Repellency and efficacy of a 65% permethrin spot-on formulation for dogs against Aedes aegypti (Diptera: Culicidae) mosquitoes.

A topically applied 65% permethrin spot-on (Defend EXspot Treatment for Dogs, Schering-Plough Animal Health) used for flea and tick control on dogs was evaluated for repellency and efficacy against the yellow fever mosquito, Aedes aegypti, a vector of canine filariasis. Six dogs were randomly assigned to receive a single application of 65% permethrin on Day 0 (n=3) or to remain untreated as controls (n=3). Dogs were anesthetized and exposed to 100 unfed, female mosquitoes in screened cages for 2 hours on Days -6, -4, -1, 0, 1, 7, 14, 21, and 28. Mosquito landing rates, engorgement rates, and mortality were determined for each mosquito challenge. Cages were thoroughly cleaned after each mosquito challenge. Treatment of dogs with 65% permethrin reduced the mosquito landing rates by 96.3% 6 hours after treatment and by 82.5% on Day 1. Mosquito mortality, relative to the control group, was 28.2% 6 hours after treatment, ranged from 84.0% to 90.9% through Day 21, and declined to 50.3% 28 days after treatment. Successful feeding by mosquitoes was significantly (P=.05) reduced on Days 1 through 28. The 65% permethrin spot-on treatment killed and repelled significantly (P =.05) more mosquitoes on treated dogs versus untreated dogs for 28 days after treatment.

Efficacy of three dose volumes of topically applied 65% permethrin against Ctenocephalides felis and Rhipicephalus sanguineus on dogs weighing 30 kg or more.

Twenty-five dogs were evenly and randomly allocated by weight to five treatment groups: untreated control, 2 ml 65% permethrin (dogs weighing 15 to 29 kg, "average dogs"), and 2, 3, or 4 ml 65% permethrin (dogs weighing > or = 30 kg, "big dogs"). Each dog was infested with 125 unfed, adult cat fleas, Ctenocephalides felis, and 50 unfed, adult brown dog ticks, Rhipicephalus sanguineus, on Days -3 (ticks only), -2 (fleas only), 3, 7, 14, 17, 21, 24, and 28. Fleas and ticks were counted 1 and 3 or 4 days after each infestation. The duration of efficacy (defined as >90%) against C. felis was 28 to 31 days. The efficacy against fleas 31 days after application of 2, 3, or 4 ml on big dogs ranged from 79.1% (2 ml) to 100% (4 ml). Big dogs that received either 3 or 4 ml of 65% permethrin had significantly (P < or = .05) fewer fleas at several evaluations between 15 and 31 days after treatment. The duration of efficacy against R. sanguineus was 15 (2 ml for big dogs) to 28 (2 ml for average dogs) days. The efficacy against R. sanguineus 28 days after treatment ranged from 79.1% (2 ml on big dogs) to 94.1% (2 ml on average dogs). Significantly (P < or = .05) fewer ticks were present at several evaluations after treatment on big dogs that received 3 or 4 ml than were present on big dogs treated with 2 ml. No significant differences were detected between the 3- and 4-ml groups from Days 10 to 31; however, the geometric mean number of ticks in the group treated with 4 ml was numerically lower than that for dogs treated with 3 ml on several occasions. These data indicate that a dose volume of 3 or 4 ml of 65% permethrin is needed to obtain an adequate level and duration of efficacy against both C. felis and R. sanguineus on dogs weighing 30 kg or more.