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  • Author or Editor: Michael W. Dryden x
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A study was conducted to determine whether cythioate, a systemically active insecticide, has different activity against male and female Ctenocephalides felis, the cat flea.

Eighteen cats were allotted equally to 1 control and 2 treatment groups and infested on day 0 with fixed ratios of male and female cat fleas. Cats in the untreated control group and treatment group 2 were infested with 50 fleas with a female-to-male ratio of approximately 2:1. Cats in treatment group 1 were infested with 50 fleas with a female-to-male ratio of 1:1. Cythioate was administered orally to cats in the treatment groups at the dosage of 3.6 mg/kg of body weight once daily on days 0 and 3. Fleas remaining after treatment were removed, sexed, and counted on day 5.

The efficacy of cythioate after 2 dosings was 82.8 and 33.4% against female and male fleas, respectively. The greater activity against female fleas resulted in posttreatment female-to-male ratios in treatment groups 1 and 2 of 0.32:1 and 0.54:1, respectively. Fleas recovered from untreated control cats had a final female-to-male ratio of 2.27:1. Total population control efficacies for treatment groups 1 and 2 were 61.7 and 67.6%, respectively.

Free access
in American Journal of Veterinary Research


Objective—To determine pharmacokinetics, efficacy, and adverse effects of topically administered selamectin in flea-infested rabbits.

Animals—18 healthy 5-month-old New Zealand White rabbits.

Procedures—On day 0, rabbits (n = 6/group) received topically applied selamectin at doses of 10 or 20 mg/kg or received no treatment. Each rabbit was infested with 50 fleas (Ctenocephalides felis) on days −1, 7, and 14. Live and dead flea counts were performed on days 2, 9, and 16, and treatment efficacy was calculated. Blood samples were collected prior to drug administration and at 6 and 12 hours and 1, 2, 3, 5, 7, 10, 14, 21, and 28 days after treatment for determination of plasma selamectin concentrations via high-performance liquid chromatography with mass spectrometry. Pharmacokinetic parameters were determined.

Results—On day 2, efficacy of selamectin against flea populations of rabbits in the 10 and 20 mg/kg treatment groups was 91.3% and 97.1%, respectively, but by day 9, these values decreased to 37.7% and 74.2%, respectively. Mean terminal half-life and maximum plasma concentrations of selamectin were 0.93 days and 91.7 ng/mL, respectively, for rabbits in the 10 mg/kg group and 0.97 days and 304.2 ng/mL, respectively, for rabbits in the 20 mg/kg group. No adverse effects were detected.

Conclusions and Clinical Relevance—Selamectin was rapidly absorbed transdermally and was rapidly eliminated in rabbits. Results suggested that topical administration at a dosage of 20 mg/kg every 7 days is efficacious for treatment of flea infestation in rabbits. Further studies are needed to assess long-term safety in rabbits following repeated applications.

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in American Journal of Veterinary Research


To evaluate imidacloprid and the combination of lufenuron and pyrethrin to control flea infestations in households with pets.


37 dogs and 19 cats in 34 flea-infested households.


Households were assigned randomly to 1 of 2 groups. Pets in group 1 were treated topically with imidacloprid on day 0, then once a month for 90 days. Pets in group 2 were given lufenuron orally on day O and at monthly intervals for 90 days and also were treated topically with a pyrethrin spray every 1 to 2 weeks throughout the study. Flea numbers in homes were assessed by use of intermittent light traps, and flea burdens on pets were assessed using visual area counts done once a week during the first month, then every other week.


One application of imidacloprid reduced flea burdens on pets by 96 and 93.5% on days 7 and 28, respectively, compared with day-O burdens. Following 3 applications, flea burdens on pets and in homes were reduced by 98.8 and 99.9%, respectively. Lufenuron and pyrethrin spray reduced flea numbers on pets by 48.9 and 91.1% on days 7 and 28, respectively. By the end of the study, this combination reduced flea burdens on pets and in homes by 99.2 and 99.7%, respectively.

Conclusions and Clinical Relevance

Imidacloprid applied topically or lufenuron administered orally along with a topically applied pyrethrin spray were effective in eliminating fleas on pets and in homes. Flea control can be achieved with topical application of adulticides or oral administration of insect growth regulators without concomitant treatment of the surroundings. (J Am Vet Med Assoc 1999;215:36-39)

Free access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association


Objective—To determine efficacy of treatment with a combination febantel-praziquantel-pyrantel product, with or without vaccination with a commercial Giardia vaccine, in dogs with naturally occurring giardiasis.

Design—Prospective trial.

Animals—16 Beagles naturally infected with Giardia duodenalis.

Procedures—During phase 1, 6 dogs were treated with the parasiticide for 3 days (4 were also vaccinated). Four weeks later, all 6 dogs were treated with the parasiticide again for 5 days and were bathed and moved to clean cages after the last treatment (phase 2). Nine dogs were treated with the parasiticide for 3 (n = 4) or 5 (5) days and bathed and moved to clean cages after the last treatment (phase 3). Fecal samples were collected twice weekly for 24 days after treatment and tested for cysts with a quantitative zinc sulfate flotation technique and for Giardia antigen with an immunoassay.

Results—Dogs in phase 1 were all shedding cysts again by day 24. In phase 2, only 1 dog shed cysts after treatment, and shedding was transient (day 17). In phase 3, neither cysts nor antigen was detected in fecal samples from 2 of 4 dogs treated for 3 days and 4 of 5 dogs treated for 5 days. In 18 of 57 (31.6%) fecal samples, cysts were seen, but results of the immunoassay were negative.

Conclusions and Clinical Relevance—Results suggest that when a combination febantel-praziquantelpyrantel product is used to treat dogs with giardiasis, bathing and changing the environment after treatment may be more important in preventing recurrence than duration of treatment. (J Am Vet Med Assoc 2002;220:330–333)

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in Journal of the American Veterinary Medical Association