Laboratory Evaluation of the Efficacy of 10 % Imidacloprid + 2.5 % Moxidectin Topical Solution (Advantage® Multi, Advocate®) for the Treatment of Dirofilaria immitis Circulating Microfilariae in Dogs.

This study examined the efficacy of 10 % imidacloprid + 2.5 % moxidectin topical solution (Advantage ® Multi, Advocate®, Bayer) for the treatment of circulating microfilariae from dogs naturally infected with Dirofilaria immitis. The study included two groups of 11 dogs each that consisted of two replicates. Replicate 1 contained 12 dogs (6 treated and 6 controls) and replicate 2 contained 10 dogs (5 treated and 5 controls). Six of the 10 dogs in replicate 2 were the controls from replicate 1. All dogs entering the study completed a physical examination including chest radiographs, blood collections for examination of Dirofilaria immitis circulating microfilariae, serum chemistry, complete blood counts and urinalysis. To qualify for the study each dog was required to have a geometric mean ≥ 300 microfilariae per ml of blood from 3 consecutive samples collected during the 8 day acclimation period and a heartworm disease classification of 1 or 2. Dogs were treated on study days 0 and 28. Post-treatment microfilarial counts were performed on study days 1, 2, 3, 7, 14, 21, 28, 29, 35, and 42. Percent microfilarial reduction was determined by comparing the geometric mean number of circulating microfilaria remaining in treated dogs with those remaining in the control dogs post-treatment. Seven days after the first treatment, the geometric mean microfilarial counts in treated dogs were reduced by > 99 % compared to the control dogs. Reduction remained at > 99 % through the end of the study at 42 days after the first treatment (14 days after the second treatment). The results of this study demonstrated that Advantage® Multi for dogs is efficacious for treatment of circulating D. immitis microfilariae in naturally infected heartworm-positive dogs with no treatment-related adverse events observed.

Efficacy of an imidacloprid 10 % / flumethrin 4.5 % collar (Seresto®, Bayer) for preventing the transmission of Cytauxzoon felis to domestic cats by Amblyomma americanum.

Infection of Cytauxzoon felis in domestic cats produces a severe disease characterised by fever, lethargy, inappetence, anorexia, depression, dehydration, icterus and often death. Transmission of C. felis to cats is dependent on being fed upon by infected Amblyomma americanum (lone star ticks). The purpose of the present study was to determine if application of a 10 % imidacloprid/4.5 % flumethrin collar (Seresto®, Bayer) on cats prevents transmission of C. felis by repelling ticks. Twenty cats were randomised to either a treated (n = 10) or non-treated control group (n = 10) based on their susceptibility to ticks. Cats of high, medium and low tick susceptibility were represented in both groups. Treated cats were fitted with 10 % imidacloprid/4.5 % flumethrin collars on study day 0 and both groups were then infested with C. felis-infected A. americanum on study day 30. Tick thumb counts were performed at 24 and 48 hours post infestation. Transmission of C. felis was determined by examining blood of cats by DNA extraction followed by PCR amplification with piroplasm-specific primers. Ticks did not attach to any of the 10 % imidacloprid/4.5 % flumethrin- treated cats. However, ticks attached and fed on all the non-treated control cats. The geometric mean number of ticks attached to the non-treated control cats at 24 and 48 hours was 15.3 and 14.2, respectively. Cytauxzoon felis was transmitted to 9 of 10 (90 %) non-treated control cats; C. felis was not transmitted to any of the treated cats. Transmission of C. felis to the non-treated cats was first detected between 8 and 16 days post infestation. Our results indicate that application of the 10 % imidacloprid/4.5 % flumethrin collar to cats prevented ticks from attaching, feeding and transmitting C. felis.

Efficacy of four commercially available heartworm preventive products against the JYD-34 laboratory strain of Dirofilaria immitis.

BACKGROUND: Heartworm disease in dogs can be severe and life threatening. Resistance to available heartworm preventives was considered among potential causes of increased reports of failed heartworm prevention in dogs. The objective of the present study was to compare the efficacy of four commercially available heartworm disease preventives against the JYD-34 strain of D. immitis. METHODS: Forty laboratory-reared dogs approximately 6 months old were used. Each dog was infected with fifty, third-stage heartworm larvae on study day (SD) -30. On SD-1, the dogs were randomized to five groups of eight dogs each. On SD-0, dogs in groups 1-4 were treated as follows: Group 1: ivermectin/pyrantel pamoate chewable tablets; Group 2: milbemycin oxime/spinosad tablets; Group 3: selamectin topical solution; and Group 4: imidacloprid/moxidectin topical solution. Dogs in Group 5 were not treated and served as controls. The dogs were treated according to their current body weights and labelled dose banding for each product. Groups 1, 2, and 3 were retreated with their respective products and current body weights on SD 31 and 60. On SDs 124-126 the dogs were euthanized and necropsied for recovery of adult heartworms. RESULTS: Adult heartworms were recovered at necropsy from each of the dogs in the control group (13-32 worms/dog, geometric mean (GM) = 18.4 worms/dog). Adult heartworms and/or worm fragments were also recovered from each of the dogs treated with ivermectin/pyrantel pamoate, milbemycin oxime/spinosad or selamectin. Geometric means of worms recovered from dogs in each of these groups were 13.1, 8.8, and 13.1, resulting in efficacies compared to controls of 29.0, 52.2, and 28.8 %, respectively. All dogs in Group 4 (imidacloprid/moxidectin) were free of adult heartworms (100 % efficacy). CONCLUSIONS: The combination of imidacloprid/moxidectin was 100 % effective in this study in preventing development of JYD-34 laboratory strain of D. immitis in dogs following a single treatment, while three monthlytreatments of the three other commercial products provided less than 100 % efficacy. The high efficacy achieved with imidacloprid/moxidectin was likely due to the unique pharmacokinetic properties of the topical formulation delivering greater and sustained drug concentrations necessary to prevent development of D. immitis larvae.

Evaluation of the efficacy of topically administered imidacloprid + pyriproxyfen and orally administered spinosad against cat fleas (Ctenocephalides felis): Impact of treated dogs on flea life stages in a simulated home environment.

BACKGROUND: Cat fleas, Ctenocephalides felis, are one of the most common ectoparasites infesting dogs and their environments. This study evaluated the efficacy of imidacloprid + pyriproxyfen (PPF) (Advantage® II for Dogs) and spinosad (Comfortis®) against established C. felis populations in dogs' simulated home environments. METHODS: Thirty Beagle dogs were randomly assigned to three groups of 10 dogs each and treated twice (Study Days 0 and 28) with imidacloprid + PPF, spinosad tablets, or a negative control (untreated). Dogs were housed individually in controlled simulated home environments capable of supporting the flea life cycle. Flea infestations were established in these environments by infesting each dog with 100 adult cat fleas on Study Days -21, -16 and 1. The impact of the treatments on fleas in the dogs' environments were assessed by collecting floor mat samples from each simulated home environment, incubating them for 32 days, and counting the number of emerging adult fleas. On Study Days 7, 14, 21, 28, 35, 42, 49 and 56, after collection of the cocoa matting samples, each dog was infested with an additional 5 ± 1 fleas to maintain the environmental infestations. Flea comb counts on dogs were conducted on Study Days 0 (pretreatment) and 63. RESULTS: From Study Days 7-28, flea infestations in the imidacloprid + PPF environments were significantly lower (p < 0.03) than those in the spinosad environments. Following the second treatment, flea infestations in all the imidacloprid + PPF environments fell to zero for the remainder of the study. In contrast, flea infestations persisted in some of the spinosad environments through the study's end.On Study Day 63 all 10 dogs treated with imidacloprid + PPF were flea free, while only one of the 10 spinosad treated dogs was flea free. Flea counts on the other 9 spinosad treated dogs ranged from 3 to 46 fleas/dog (geometric mean = 8.6). A mean of 405 adult fleas/animal were recovered from the control dogs on Study Day 63. CONCLUSION: Flea infestations in environments of dogs treated with imidacloprid + PPF declined more rapidly than in those containing dogs treated with spinosad. Flea infestations were completely eliminated by Study Day 56 in environments of dogs treated with imidacloprid + PPF, but persisted through the study's end in some of environments of dogs treated with spinosad.

Mites and lice: biology and control.

Dogs and cats frequently encounter a diverse variety of mite and lice species, which may result in mild to severe consequences depending on husbandry conditions, the severity of the infestation, and the nature of the localized or systemic defense mechanisms mobilized by the host in response to the parasite. Some of these external parasites are obvious to detect, identify, and control, although others may offer a significant challenge to the practitioner. Traditional acaricide and insecticide formulations, including dips, sprays, powders, and shampoos, have been used to treat and control these infestations. Some of the more recently developed, low-volume, topically applied insecticides and systemically acting macrolide formulations, although not always labeled for specific claims, may offer safe, efficacious, and convenient alternatives. The practitioner may wish to consider these products when implementing treatment and control programs involving these pests.