Defining the concept of 'tick repellency' in veterinary medicine.

Although widely used, the term repellency needs to be employed with care when applied to ticks and other periodic or permanent ectoparasites. Repellency has classically been used to describe the effects of a substance that causes a flying arthropod to make oriented movements away from its source. However, for crawling arthropods such as ticks, the term commonly subsumes a range of effects that include arthropod irritation and consequent avoiding or leaving the host, failing to attach, to bite, or to feed. The objective of the present article is to highlight the need for clarity, to propose consensus descriptions and methods for the evaluation of various effects on ticks caused by chemical substances.

Study of the sustained speed of kill of the combination of fipronil/amitraz/(S)-methoprene and the combination of imidacloprid/permethrin against Dermacentor reticulatus, the European dog tick.

The sustained speed of kill against Dermacentor reticulatus of two topical combinations, one containing fipronil/amitraz/(S)-methoprene and the other, imidacloprid/permethrin, was evaluated in dogs. Two treated groups and one untreated control group of eight adult Beagle dogs each were randomly formed based on pre-infestation rates and bodyweight. Each treatment was administered topically once on Day 0, according to the recommended label dose and instructions for use. All dogs were infested with 50 adult unfed D. reticulatus starting on Day 1, then weekly, for a total of five weeks. While most studies determine tick efficacy at 48 hours (h), in this study, all remaining ticks were counted and categorized 24 h following each infestation. The numbers of ticks (living or dead) that remained attached on treated dogs were compared to those on the control animals. The percent reduction of attached ticks (disruption of attachment) at 24 h on dogs treated with fipronil/amitraz/(S)-methoprene remained above 92% for four weeks. The reduction of attached ticks at 24 h on dogs treated with imidacloprid/permethrin did not reach 80% during the entire study. The number of ticks attached at 24 h was significantly (p<0.05) lower in the fipronil/amitraz/(S)-methoprene group than in the imidacloprid/permethrin group in assessments on Days 2, 15, 22, 29 and 36. When assessing efficacy based upon live ticks on treated versus control dogs, fipronil/amitraz/(S)-methoprene 24 h efficacy was above 95% for four weeks, decreasing to 77.8% at Day 36. The 24 h efficacy of imidacloprid/permethrin ranged from 56.2% to 86.7% through Day 29, never achieving 90% throughout the study. The 24-hour efficacy of fipronil/amitraz/(S)-methoprene was significantly (p<0.05) higher than imidacloprid/permethrin at all time points, including Day 36.

Comparative acaricidal efficacy of the topically applied combinations fipronil/(S)-methoprene, permethrin/imidacloprid and metaflumizone/ amitraz against Dermacentor reticulatus, the European dog tick (ornate dog tick, Fabricius, 1794) in dogs.

The acaricidal efficacy against Dermacentor reticulatus in dogs of the commercial topical combinations fipronil/(S)-methoprene (FRONTLINE Combo spot-on dog), imidacloprid/permethrin (Advantix) and metaflumizone/amitraz (ProMeris Duo) was evaluated and compared. Three treatment groups and one untreated control group of six adult Beagle dogs each were randomly formed. Each treatment was administered topically once on Day-0, according to the recommended label dose and instructions for use. All dogs were infested weekly with approximately 50 adult unfed D. reticulatus over a period of seven weeks. Ticks were removed and counted approximately 48 hours after each infestation. The percent reduction in numbers of ticks for fipronil/(S)-methoprene was > or = 97% compared to untreated controls for all seven weekly infestations. The percent reductions for imidacloprid/permethrin and metaflumizone/amitraz were satisfactory initially but fell and stayed below 90 % after three weeks. From the third week onwards, fipronil/(S)-methoprene treated dogs had significantly fewer ticks than imidacloprid/permethrin or metaflumizone/amitraz treated dogs (p < 0.05).

The use of force plate measurements to titrate the dosage of a new COX-2 inhibitor in lame horses.

REASONS FOR PERFORMING STUDY: Lameness is a highly prevalent condition in horses and the principal cause of removal from athletic activity. In clinical studies to evaluate nonsteroidal anti-inflammatory drug therapies, force plates are commonly used to assess improvement of lameness objectively. HYPOTHESIS: To use a force plate to determine the optimal dose of a new COX-2 inhibitor (firocoxib) that will reduce lameness, when administered orally to horses once daily. METHODS: Sixty-four horses that exhibited chronic lameness presumed due to osteoarthritis, including navicular disease, in at least one of the frontlimbs and at a stable level of severity, were included. Horses were treated per os s.i.d. for 7 days as follows: vehicle control, firocoxib at 0.05, 0.1 or 0.25 mg/kg bwt. Force plate analysis of each horse was done for the selected (most) lame frontlimb at trot. Once between Days -19 and -4 (initial examination), and again on Day -2 or -1 (baseline), pretreatment force plate assessments were performed, and thereafter horses were assessed on Days 0, 2 and 6, approximately 10 h post treatment each time. Peak vertical force (PVF) and lameness grades at initial examination and at baseline, and their change from baseline in the 4 different treatment groups were analysed statistically at a significance level of P < 0.05. RESULTS: The PVF results were found to be superior to vehicle control already at Day 0 for 0.25 mg/kg bwt and at Days 2 and 6 for 0.1 and 0.25 mg/kg bwt (P < 0.05). Mean clinical lameness for both concentrations decreased > 1 grade at Day 6. CONCLUSIONS AND CLINICAL RELEVANCE: With the dosage of 0.25 mg/kg bwt lameness did not improve more than with 0.1 mg/kg bwt. Thus, 0.1 mg/kg bwt s.i.d. was considered to be the effective dose at reducing chronic lameness in horses presumed due to osteoarthritis, including navicular disease.

The groove model of osteoarthritis applied to the ovine fetlock joint.

OBJECTIVE: Until now there have been no appropriate models for metacarpophalangeal osteoarthritis (OA), even though OA in this joint is a significant medical and economic problem in horses. A good model would be useful to evaluate progression and treatment of OA, particularly in this joint. Therefore, we translated the canine Groove model to the ovine metacarpophalangeal (fetlock) joint. METHOD: Cartilage surfaces of the metacarpal side of one fetlock joint were surgically damaged (grooved), followed by intermittent forced loading of the experimental joint. After 15 and 37 weeks, cartilage, synovial tissue and subchondral bone were analyzed by the use of macroscopy, histology, biochemistry and micro-CT. RESULTS: Technically, the model was difficult to use because cartilage surfaces were very thin. Nonetheless, all macroscopic, histologic, and biochemical cartilage parameters demonstrated adverse changes in chondrocyte activity and matrix integrity. Decreased proteoglycan content suggested slow progression of cartilage degeneration over time, while synovial inflammation diminished. Impaired subchondral bone quality and osteophyte formation were found. Although osteophyte formation was progressive, subchondral bone changes diminished over time. CONCLUSION: The canine Groove model appears to a limited extent transferable to the ovine fetlock joint. However, despite development of adverse changes consistent with early changes of OA, use of the Groove model in the ovine fetlock joint has technical limitations. Using larger animals, such as horses, may significantly improve the technical procedures and with that may provide a more reliable model of metacarpophalangeal OA that is based primarily on intrinsic cartilage damage, appropriate to evaluate the progression and treatment of OA in this particular joint.

Pharmacokinetics and metabolism of orally administered firocoxib, a novel second generation coxib, in horses.

The primary objective of this study was to determine the pharmacokinetic profile of firocoxib, a novel second generation coxib, in horses. Horses were administered either a single oral or intravenous dose of firocoxib at 0.1 mg/kg in a two-period crossover study with 12 animals. The dosage was based on previously determined pharmacodynamic parameters. Oral firocoxib was well absorbed with an average bioavailability (absolute) of 79% and a Cmax of 75 ng/mL at 3.9 h. The average elimination half-life was 30 h. Following intravenous administration the average Cmax was 210 ng/mL and the elimination half-life was 34 h. The area under the curve [AUC(0-tlast)] was 1.8 microg.h/mL for the oral dose and 2.3 microg.h/mL for the intravenous dose. Firocoxib was widely distributed with a volume of distribution value of 1.7 L/kg for the intravenous dose. Biotransformation of firocoxib was via dealkylation and glucuronidation to inactive metabolites, namely descyclopropylmethylfirocoxib and its glucuronide conjugate. Urinary excretion was the major route of elimination, and the clearance rate was 37 mL/h/kg.

A kinetic study of histopathological changes in the subcutis of cats injected with non-adjuvanted and adjuvanted multi-component vaccines.

The aim of this study was to investigate the subcutaneous tissue response to administration of a single dose of multi-component vaccine in the cat. Three groups of 15 cats were injected with one of three vaccine products with saline as a negative control. Cats in group A received non-adjuvanted vaccine; cats in group B received vaccine with a lipid-based adjuvant; whilst those in group C were vaccinated with a product adjuvanted with an alum-Quil A mixture. The vaccine and saline injection sites were sampled on days 7, 21 and 62 post-vaccination. Biopsies of these vaccine sites were examined qualitatively and scored semi-quantitatively for a series of parameters related to aspects of the inflammatory and tissue repair responses. These data were analysed statistically, including by principal component analysis. At all three time points of the experiment, there was significantly less inflammation associated with administration of non-adjuvanted vaccine (p=0.000). Although there was evidence of tissue repair by day 62 in all groups, those cats receiving adjuvanted vaccines had evidence of residual adjuvant material accumulated within macrophages at this late time point. The severity of tissue reactions may vary significantly in response to vaccines which include adjuvants or are non-adjuvanted.

Clinical evaluation of firocoxib and carprofen for the treatment of dogs with osteoarthritis.

A double-blind, randomised, controlled, multicentre field study was conducted to compare the safety and efficacy of firocoxib chewable tablets and carprofen tablets in 218 dogs with osteoarthritis. Firocoxib is a non-steroidal anti-inflammatory drug with more than 350-fold selectivity in dogs for the inducible isoform of the enzyme cyclo-oxygenase-2. The efficacy, tolerance and ease of administration of firocoxib (5 mg/kg/day) and carprofen (4 mg/kg/day) were assessed by the owners and the attending veterinarians during 30 days of treatment. The efficacy was assessed in terms of the dogs' overall scores at the end of the treatment, based on the veterinarians' assessment of lameness, pain on manipulation/palpation, range of motion, and joint swelling; 92.5 per cent of the dogs treated with firocoxib and 92.4 per cent of the dogs treated with carprofen had improved. The reduction in lameness in the dogs treated with firocoxib was significantly greater than in the dogs treated with carprofen. The owners' evaluations were that 96.2 per cent of the dogs treated with firocoxib and 92.4 per cent of the dogs treated with carprofen had improved, and this difference was statistically significant.

Efficacy of fipronil in the treatment of feline cheyletiellosis.

The purpose of the present study was to confirm the efficacy of 10% (w/v) fipronil spot-on (Frontline spot-on for cats) in the treatment of feline cheyletiellosis under field conditions. A total of 16 cats of different breeds, sexes, 4 months to 14 years of age and weighing 0.5-6 kg were treated with a single topical application of 10% (w/v) fipronil spot-on according to label directions. The animals were naturally infested with Cheyletiella mites and housed in their normal environment throughout the study. Animals were selected based on clinical signs and infestation was confirmed by demonstration of mites. Mite counts and a clinical assessment of mite infestations (i.e. skin lesions and/or scales) were performed on days 0 and approximately days 14 and 28. Individual counts on day 0 ranged from 1 to 40 mites on individual animals. No mites were detected on cats treated with 10% (w/v) fipronil spot-on (Frontline spot-on for cats) at both post-treatment evaluations. Typical skin lesions and/or scales were present in all animals pre-treatment. In 56% of the cats, the lesions resolved within 14 days after treatment. At the final assessment, 75% cats were free of lesions. Two cats that still had clinical signs on day 28 were suspected of having allergic reactions to food or environmental allergens. The lesions on the remaining two cats could not be related to a specific cause. The efficacy of fipronil in elimination of mites was 100% on each occasion when compared to the pre-treatment count. The results of this study demonstrated that fipronil in a topical formulation is highly effective (100%) for the elimination of an existing Cheyletiella mite infestation under field conditions following a single topical application in cats.

Effective treatment and control of biting lice, Felicola subrostratus (Nitzsch in Burmeister, 1838), on cats using fipronil formulations.

The efficacy of 0.25% fipronil spray (Frontline Spray, Merial), 10% fipronil spot-on (Frontline Spot-on for Cats, Merial) and 10% fipronil/12% (S)-methoprene (Frontline Plus for Cats, Merial) against the biting louse Felicola subrostratus on cats was assessed and confirmed under laboratory conditions. A field study evaluated the efficacy of a single topical application of Frontline Spray, and spot-on against the parasite on cats. In the laboratory studies, animals were allocated based on pre-treatment louse counts to the treatment groups: (1) untreated control and (2) 10% fipronil spot-on in the exploratory study or (1) untreated control, (2) 0.25% fipronil spray, at 6 ml/kg; (3) 10% fipronil spot-on as per label and (4) 10% fipronil/12% (S)-methoprene as per label in the confirmation study. Cats in treatment groups 2-4 were treated twice topically on Days 0 and 28. No live F. subrostratus were found on cats treated with fipronil formulations at any post-treatment examination. The difference from controls was significant (P < 0.01) for each product at each examination. Based on whole body counts at Day 42, the efficacy of each product was determined to be 100%. In the field study, cats were allocated in strict order of presentation. Cats were randomly allocated to one of the three treatment groups: (1) propoxur collar (Bolfo, Bayer); (2) 0.25% fipronil spray, at 6 ml/kg and (3) 10% fipronil spot-on as per label. Cats were treated once topically on Day 0. Louse counts of cats treated with fipronil formulations were not different than those of cats receiving the propoxur collar. The efficacy was determined to be > 98% on Day 2 and 100% on Days 28 and 42 in all treatment groups. The results of these studies demonstrate that fipronil in topical formulations is effective for treatment and control of biting lice (F. subrostratus) infestations on cats.

Reduced dosage of ketoprofen for the short-term and long-term treatment of joint pain in dogs.

Two studies were conducted under laboratory conditions with 16 dogs to investigate the analgesic effectiveness of a low dose of ketoprofen in a short-term sodium urate crystal-induced synovitis model of arthritis. The effect of the treatment, defined as the improvement in peak vertical force weight bearing was evaluated in the first study at three dose levels. A single oral dose of 0.25 mg/kg ketoprofen was significantly better (P < 0.01) than the control (0 mg), but doses of 0.5 and 0.75 mg/kg did not improve the dogs' weight bearing further. The second study investigated the efficacy and safety of the 0.25 mg/kg dose administered daily for 30 days. The beneficial effects of ketoprofen at this dose were constant, with the treated dogs bearing 89.1 per cent of the baseline vertical force four hours after the induction of arthritis on day 1 and 92.2 per cent on day 29, compared with 42 per cent and 34 per cent of the baseline in the untreated dogs. No gastrointestinal or other side effects were observed during the treatment.

Evaluation of the efficacy of fipronil formulations in the treatment and control of biting lice, Trichodectes canis (De Geer, 1778) on dogs.

The efficacy of FRONTLINE SPRAY (0.25% (w/v) fipronil), FRONTLINE SPOT-ON FOR DOGS (10% (w/v) fipronil) and FRONTLINE PLUS FOR DOGS (10% (w/v) fipronil and 9% (S)-methoprene) against the biting louse Trichodectes canis on dogs was confirmed under laboratory conditions. A field study evaluated the efficacy of a single topical application of FRONTLINE SPRAY and FRONTLINE SPOT-ON against the parasite on dogs. A total of 48 dogs of mixed breeds, both sexes, aged 2 months-7 years and weighing 1.8-37.0kg were used. The animals were either experimentally (laboratory study) or naturally (field study) infested with lice. Dogs were housed individually in order to prevent contact between animals. In the laboratory study, animals were allocated based on pre-treatment louse counts from 38 hair coat-partings per animal. Dogs were randomly assigned to the four treatment groups: (1) untreated control; (2) FRONTLINE SPRAY, at 6ml/kg; (3) FRONTLINE SPOT-ON as per label and (4) FRONTLINE PLUS as per label. Dogs in treatment groups 2-4 were treated twice topically on Days 0 and 28. The number of live lice in the 38 hair coat-partings per animal were counted on Days 2, 7 and weekly to Day 63. In addition, a whole body comb count was performed on Day 63. No live T. canis were found on dogs treated with FRONTLINE formulations at any post-treatment examination. The difference from controls was significant (P<0.01) for each product at each examination. Based on the whole body comb count at Day 63, the efficacy of each product was determined to be 100%. In the field study, dogs were allocated in strict order of presentation. Dogs were randomly allocated to one of the three treatment groups: (1) BOLFO collar (propoxur); (2) FRONTLINE SPRAY, at 6ml/kg and (3) FRONTLINE SPOT-ON as per label. Dogs were treated once topically on Day 0. The number of live lice was determined by whole body searches on Days 0 (pre-treatment), 2, 28 and 42. Louse counts of dogs treated with either FRONTLINE SPRAY, or FRONTLINE SPOT-ON were not different than those of dogs receiving the propoxur collar. The efficacy was determined to be >98% on Day 2 and, 100% on Days 28 and 42 in all treatment groups. The results of these studies demonstrate that fipronil in topical formulations is effective for treatment and control of biting lice (T. canis) infestations on dogs.

High-performance liquid chromatographic assay for the determination of a semisynthetic avermectin analog (eprinomectin) in bovine milk at parts per billion levels--method development and validation.

A sensitive and automated method has been developed and validated to determine marker residue eprinomectin B(1a) in bovine milk. Extraction of eprinomectin B(1a) from milk is accomplished with acetonitrile after the addition of an internal standard. The extract containing the analytes is evaporated to dryness and reconstituted in a solution containing 30% 1-N-methylimidazole in acetonitrile. Online derivatization is carried out with trifluoroacetic anhydride. Determination of eprinomectin B(1a) and its internal standard is carried out by HPLC using a reversed-phase C(18) column with a mobile phase consisting of methanol, acetonitrile, water, triethylamine and phosphoric acid. The overall extraction recovery of eprinomectin B(1a) is 94% with milk supplemented between 2 and 50 ng/ml eprinomectin B(1a). Precision RSD averaged 3.0% in Laboratory 1 (n=25) compared to 4.3% in Laboratory 2 (n=35). The limit of quantitation is approximately 2 ng/ml eprinomectin B(1a), the limit of detection is approximately 0.25 ng/ml using this method.

Acceptability of a paste formulation and efficacy of high dose omeprazole in healing gastric ulcers in horses maintained in race training.

Gastric ulceration has been found to occur in 80-90% of Thoroughbreds in active race training. Previously, variable success has been reported using mucosal surface protectants and H2 receptor antagonist. Omeprazole, a substituted benzimidazole, has been shown to inhibit gastric acid secretion in both man and animals. Fourteen horses, in active race training and with endoscopic evidence of moderated to severe gastric ulceration were divided into 2 groups: Group 1 (7 horses) were given placebo paste orally once daily for 28 days; Group 2 (7 horses) received 1.54 g active omeprazole in the placebo once daily for 28 days. Logs detailing administration and acceptability of the paste, and the horse's feeding and training regime were maintained by the trainer of each horse. Endoscopic examination of the stomach occurred at the beginning of the trial, and at 13-17 days and 27-31 days following commencement of the trial. Those horses that were free of ulceration on Days 27-31 were reexamined on Days 35-49. Acceptability of the paste, whether with or without active omeprazole, was deemed excellent in all horses except on one occasion, when one horse swallowed the paste following initial mild reluctance. Of the horses given the placebo (Group 1), 3 were withdrawn after the 13-17 day endoscopic examination: 1 horse to be given a H2 receptor antagonist, 1 horse was removed from training due to aryepiglottic entrapment and 1 horse had a greater than 10% fall in bodyweight from the start of the trial. Of the horses given active omeprazole (Group 2), one horses was relocated to another race track following the 13-17 day endoscopic examination. For the horses given placebo (Group 1), there was no change in the severity of ulceration. In contrast, the severity of ulceration in the horses given active omeprazole was significantly reduced at 13-17 days and 27-31 days. In 2 Group 2 horses, ulcers that had been completely eliminated subsequently returned when reexamined at 35-49 days. The results of this study suggest that omeprazole, employing a once daily dosing schedule, is effective at reducing the severity or eliminating gastric ulcers in Thoroughbreds in active race training.

The prevention of Dirofilaria repens infection with ivermectin/pyrantel chewables.

This trial was conducted to test the efficacy of ivermectin/pyrantel chewables in preventing the development of Dirofilaria repens in dogs. The trial included 155 dogs from an endemic area in North-Western Italy. Prior to enrollment in the study, none of the dogs had microfilariae of D. immitis or D. repens in a concentration test, and all dogs were also seronegative for adult heartworm antigen. Animals remained with their owners and were dosed six times, at monthly intervals according to body weight. Efficacy against D. repens was evaluated approximately 6 and 12 months after the first dosing. None of the treated dogs was found to harbour microfilariae of D. repens or D. immitis on either occasion, whereas 6 of 24 untreated controls had circulating D. repens microfilariae at the final testing. The treatment was well accepted by all dogs.