Robert G. Arther

Comparative efficacy of four commercially available heartworm preventive products against the MP3 laboratory strain of Dirofilaria immitis

A controlled laboratory study was conducted to evaluate the efficacy of four commercial products administered as a single treatment for the prevention of heartworm disease caused by Dirofilaria immitis in dogs. Forty-four commercially sourced Beagle dogs, 6-7 months of age, were received at the test site (Auburn University, Department of Pathobiology) on Study Day (SD) -72 to begin acclimation. On SD -30, each dog was inoculated subcutaneously with 100 infective, third-stage D. immitis larvae (MP3 strain, TRS Laboratories, Inc., Athens, GA). On SD -1, 40 dogs weighing 18.2-25.3 lbs were ranked by decreasing body weight and randomized to five groups of eight dogs each. On SD 0, the dogs assigned to Group 1 were treated orally with ivermectin/pyrantel pamoate chewable tablets, Group 2 dogs were treated orally with milbemycin oxime flavored tablets, Group 3 dogs were treated with selamectin topical solution, and Group 4 dogs were treated with imidacloprid/moxidectin topical solution. Group 5 dogs remained nontreated. Dosages for dogs in Groups 1-4 were based on the individual body weight of each dog and current labeled dose banding for each commercial product. All dogs were fasted overnight prior to treatment. Food was returned four hours after treatment. Animals were observed for abnormal clinical signs involving eyes, feces, respiration, behavioral attitude, locomotion/musculature, or skin conditions at prescribed intervals immediately after treatment and at twice daily intervals thereafter. On SD 90, whole blood was collected and tested for adult heartworm antigen. On SDs 119/120, the dogs were euthanized and subjected to necropsy examination for recovery of adult D. immitis and/or worm fragments. At necropsy, all 8 dogs in the nontreated group were infected with adult D. immitis (34-70 worms/dog, geometric mean (GM)=51.6 worms/dog). One or more adult D. immitis and/or worm fragments were recovered from 7 of 8 of the dogs each in Groups 1-3 (87.5% were heartworm positive). The respective GM worm burdens/dog for Groups 1-3 was 2.3, 2.4, and 2.3 which resulted in 95.6, 95.4 and 95.5% efficacy, respectively. No worms were recovered from any of the 8 dogs in Group 4 resulting in 100% efficacy.

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.

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.

Safety of imidacloprid plus moxidectin topical solution applied to cats heavily infected with adult heartworms (Dirofilaria immitis)

A topically applied formulation containing 10% imidacloprid+1% moxidectin (Advocate®/Advantage multi®) has been developed for monthly application to cats for the prevention of feline heartworm (HW) disease caused by Dirofilaria immitis; and for the treatment and control of flea infestations, ear mite infestations, and intestinal nematode infections. A study model was designed to evaluate the safety of this product in cats harboring adult D. immitis infections. Eighty adult cats (40 males/40 females) were each inoculated with 60 third–stage D. immitis larvae on test day (TD) 1. On TD 243–245 echocardiographic imaging was performed on each cat to confirm and estimate the number of adult D. immitis residing in the cardiovascular system. A total of 35 cats were subsequently eligible for safety evaluation based on inclusion criteria. Four treatment groups were established and randomly selected for treatment: imidacloprid+moxidectin solution at the label dose (n=9) (group 1), imidacloprid+moxidectin solution at 5x the Iabel dose (n=9) (group 2), 6% selamectin topical solution (Revolution®) at the label dose (positive control, n=8) (group 3), and topical treatment with placebo (negative control, n=9) (group 4). All cats were treated on TD 250. Treatments for groups 1, 3, and 4 were repeated on TDs 278 and 306. Group 2 cats were euthanized and examined for adult D. immitis on TD 288. All other cats were euthanized and examined for adult D. immitis on TD 334. No adverse events attributable to treatment with the test articles were observed during the study. The geometric mean numbers of adult D. immitis recovered at necropsy from treatment groups 1–4 were 2.9, 3.2., 4.0, and 2.7, respectively. There were no statistically significant differences in the comparison of adult D. immitis recovered at necropsy (ANOVA overall group effect P–value of 0.5356). The results of this study demonstrate that imidacloprid+moxidectin topical solution can be used safely in cats heavily infected with adult D. immitis.

Clinical Evaluation of the Efficacy and Safety of Topically Applied Imidacloprid plus Moxidectin against Ear Mites (Otodectes cynotis) in Client-Owned Cats

A multi-centred clinical field study was conducted to evaluate the safety and efficacy of a 10% imidacloprid / 1% moxidectin combination against ear mites (Otodectes cynotis) in client-owned cats. Veterinarians and staff from six veterinary clinics (USA) participated in the study.Single- and multi-cat households were enrolled in the study. In multi-cat households, all cats were evaluated for safety, but only one cat in the household was randomly chosen for evaluation of efficacy. Ninety-three (93) households with 332 cats were evaluated for safety, and 77 households with 301 cats were evaluated for efficacy. Each household was randomly assigned to a treatment group: imidacloprid/moxidectin or selamectin.Treatments were administered twice, approximately 30 days apart, by the cat’s owner. Otoscopic examinations were performed on the cats by the investigators for the presence of ear mites prior to treatment, and approximately 30 days after each treatment.Imidacloprid/moxidectin provided 92.5 and 98.1% ear mite efficacy following the first and second treatments, while selamectin provided 91.7 and 95.8% efficacy following the two respective treatments. No serious adverse events related to treatment with either product were observed during the study.

Safety and efficacy of 10% imidacloprid + 2.5% moxidectin for the treatment of Dirofilaria immitis circulating microfilariae in experimentally infected dogs

A controlled laboratory study was conducted to establish the safety and efficacy of 10% imidacloprid+2.5% moxidectin topical solution (Advantage Multi® for Dogs, Bayer HealthCare, Shawnee, KS) for the treatment of circulating Dirofilaria immitis microfilariae in dogs. Twenty beagles were experimentally infected with D. immitis via surgical implantation of 10 pairs of adult worms (Pepper strain, TRS Labs) from donor dogs on Day -82. Between Days -7 and -1, physical examinations were performed, chest radiographs were taken, and blood and urine samples were collected for microfilariae counts, serum chemistry, complete blood counts, and urinalysis. Each dog was required to have a mean pretreatment count of at least 300 mf/ml of blood. On Day -1, all 20 dogs were randomized by mean pretreatment microfilarial counts to two study groups (10 animals/group). Animals in Group 1 were treated on Days 0 and 28 with 10% imidacloprid+2.5% moxidectin topical solution at the minimum label dose of 0.1 ml/kg. Group 2 animals served as negative controls and were treated on Days 0 and 28 with mineral oil at an equivalent volume as for the study solution. All dogs were observed hourly for 8h after treatment, again at 12h, and then once daily on all other study days. Blood samples for microfilarial counts were collected daily for 3 days after treatment and then weekly for 6 weeks. The percentage reduction in microfilariae was determined by comparing the geometric mean number of circulating microfilariae remaining in Group 1 dogs with the mean counts remaining in control dogs. Group 1 mean microfilarial counts were reduced 93.1% three days following the first treatment and by >99% on Days 14 through 42. Group 1 had significantly fewer (p<0.05) microfilariae compared with Group 2 counts on Days 28 and 42. In addition, log-transformed geometric mean microfilarial counts were significantly different between the two groups (p<0.05) using separate repeated measures analysis of covariance for Days 2, 3, 7, 14, 21, 28, 35, and 42. No adverse events related to treatment were reported during the study. The results of this study demonstrate that 10% imidacloprid+2.5% moxidectin topical solution is efficacious for treatment of circulating D. immitis microfilariae in heartworm-positive dogs with no treatment-related adverse events observed.

Toltrazuril (Bay Vi 9142) as an anticoccidial in naturally infected goats

Abstract When administered for 14 days in drinking water to goats harboring natural coccidial infections by Eimeria arloingi, Eimeria christenseni and Eimeria alijevi , toltrazuril at 30 p.p.m., but not at 15 p.p.m., was highly effective in suppressing fecal oocyst production. The drug was not effective as a single-dose drench at 20 mg kg −1 bodyweight. The goats presented no behavioral signs of drug toxicity and the palatability of the drinking water was not reduced by the presence of the drug. It was concluded that toltrazuril holds promises as a drug of value for the control of coccidiosis in goat production.

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 aimed to evaluate the efficacy of an emodepside 2.1 % (w/v)/praziquantel 8.6 % (w/v) topical solution (Profender® spot-on for cats) in the prevention of lactogenic Toxocara cati infections. A controlled test was performed with two groups of 8 cats with confirmed pregnancy. All cats were infected with daily doses of 2000 T. cati eggs for 10 consecutive days starting 50 days post conception to produce an acute infection. Treatment was performed 60 days post conception. Queens in the treatment group received the emodepside/praziquantel solution at the minimum therapeutic dose (3 mg/kg emodepside and 12 mg/kg praziquantel), while the control group was treated with a placebo spot-on. Efficacy was evaluated 56 days post partum by necropsy of one randomly selected kitten of each litter and comparison of the worm burdens between the study groups. Additionally the necropsy results were supported by quantification of worms expelled with the faeces after deworming of the remaining kittens and all queens. The treatment in late pregnancy resulted in an efficacy of 98.7 % (p < 0.0001). All necropsied control kittens were infected (geometric mean 30.6). Seven of 8 kittens from treated mothers were free of T. cati (geometric mean 0.4). Worm counts after deworming reflected the results obtained at necropsy. No side effects of the treatment were observed. It is concluded that treatment with an emodepside/praziquantel spot-on solution during late pregnancy effectively prevents lactogenic transmission of T. cati to the offspring. The study design facilitated the generation of reliable data, while at the same time a minimum number of animals was sacrificed.