Efficacy of oral afoxolaner plus milbemycin oxime chewables against induced infestations with Dermacentor reticulatus in dogs.

The efficacy of afoxolaner plus milbemycin oxime (AFX + MO) combination chewables (NexGard Spectra®, Merial) and AFX single-entity chewables (NexGard®, Merial) against induced infestations with Dermacentor reticulatus ticks was evaluated in dogs. Thirty dogs were assigned to blocks of three animals each based on pre-allocation tick counts and were randomly allocated to one of three groups: untreated (control), treated with a combination of AFX + MO chewables to be as close as possible to the minimum effective dose of AFX + MO (2.5 + 0.5 mg per kg body weight), and treated with a combination of NexGard® chewables to be as close as possible to the minimum effective dose of AFX (2.5 mg per kg body weight). Treatments were administered orally once on day 0. Starting 2 days before treatment administration, each dog was infested with approximately 50 ticks weekly for six consecutive weeks. Live ticks were counted at ∼48 h post-treatment (removal count) and at ∼48 h (in situ counts) and ∼72 h (removal counts) following each post-treatment infestation. Treatment with both AFX + MO and NexGard® chewables rapidly eliminated the existing tick infestations (100 % efficacy) within 2 days following treatment administration. Weekly re-infestations were controlled for a minimum of 5 weeks with the efficacy ranging from 92.2 to 99.7 % based on ∼48 h post-treatment in situ counts and between 99.0 and 100 % based on ∼72 h post-treatment removal counts (p < 0.0001 at each occasion). This study demonstrated a high efficacy of both AFX + MO chewable and NexGard® chewable treatments against infestations of dogs with D. reticulatus ticks for at least 5 weeks. In addition, this study indicated no interference between the two compounds with respect to the acaricidal activity provided by AFX.

One-month comparative efficacy of three topical ectoparasiticides against adult brown dog ticks (Rhipicephalus sanguineus sensu lato) on mixed-bred dogs in controlled environment.

This study was designed to compare the therapeutic and residual efficacy for 1 month of three topical ectoparasiticides on mixed-bred dogs against the brown dog tick, Rhipicephalus sanguineus. Adult dogs (n = 32, 10.8-18.4 kg BW) were allocated to 4 groups (n = 8) and infested with 50 adult ticks on days -8, -2, 7, 14, 21, and 28. Within each group, dogs were treated topically on day 0 with a control solution (CS), Vectra 3D (DPP), Frontline Plus (FM), or K9 Advantix (IP). Ticks were enumerated on dogs 24 h after treatment and each subsequent tick infestation by in situ thumb count assessment without removal and at 48 h by combing and removal. Acaricidal efficacy was calculated using arithmetic means for all 24 and 48 h tick count assessments. From 42 to 56% of the total, infested ticks were found on dogs 48 h post-challenge in the CS group. Therapeutic efficacy for all treatments ranged from 45.5 to 64.6% after 48 h of infestation. Residual efficacy after FM treatment was consistently lower compared to DPP or IP treatments at the 24 h assessments on days 8, 22, 23, and 29. Residual efficacy measured at this last time point was 94.8% for DPP, 83.1% for IP, and 46.9% for FM. This study demonstrates that permethrin-based formulations (DPP and IP) provided a quicker onset of residual protection against brown dog ticks compared to FM. Although DPP and IP are both permethrin-based formulations, DPP exhibited consistently higher residual acaricidal efficacies and was the only treatment that provided >90% protection for 1 month at 24 h post challenge.

Expellency, anti-feeding and speed of kill of a dinotefuran-permethrin-pyriproxyfen spot-on (Vectra®3D) in dogs weekly challenged with adult fleas (Ctenocephalides felis) for 1 month-comparison to a spinosad tablet (Comfortis®).

This study was designed to compare the efficacy of two ectoparasiticides against adult fleas on dogs: a topical (DPP, dinotefuran-permethrin-pyriproxyfen) and a systemic (S, spinosad). Dogs (n = 48; 10.21-22.86 kg BW) were allocated to six groups of eight dogs each (C1, C4, DPP1, DPP4, S1, S4). Dogs in the treated groups were administered a topical (3.6 mL of DPP) or a tablet (665 or 1040 mg of S) on day 0. Infestations with 100 unfed fleas (Ctenocephalides felis) occurred on days -6, -1, 2, 7, 14, 21 and 28. An additional untreated group (QC, n = 6) was involved to evaluate the flea-anti-feeding efficacy. These dogs were infested once with 150 fleas prior to combing of at least 50 live fleas from each dog 5 or 10 min after infestation. In the treated group, dislodged dead and moribund fleas were collected from dogs 5, 10, 15 and 60 min (DPP1, S1) or 5, 10, 30 and 240 min (DPP4, S4) post-treatment and subsequent flea infestations on pans placed underneath the cages. Fleas were counted and removed from dogs by combing 1 (C1, DPP1, S1) or 4 h (C4, DPP4, S4) post-treatment and subsequent infestations. Quantitative PCR analysis of the canine cytochrome b gene was conducted on dislodged fleas collected from treated and control (QC) dogs 5 and 10 min after post-treatment infestations. The number of gene copies was used as a marker of blood volume ingested by fleas. Dislodgeability and insecticidal efficacy were calculated using arithmetic means. A rapid onset of killing was observed for DPP with 12.7 % of dead and moribund fleas being dislodged in average from dogs as soon as 5 min after infestation. DPP exhibited a significantly higher and sustained speed of kill than S. The average insecticidal efficacy was 86 ± 8.8 and 95.3 ± 2.1 % with DPP, whereas it was only 33.7 ± 19.9 and 57.6 ± 18.6 % with S at respectively 1 and 4 h after weekly reinfestations. The DPP combination significantly inhibited the feeding of fleas (89 % reduction) up to onset of flea mortality for 1-month post-treatment.

Comparative Speed of Kill, Repellent (anti-feeding) and Acaricidal Efficacy of an Imidacloprid/Flumethrin Collar (Seresto®) and a Fipronil/(S)-Methoprene/Eprinomectin/Praziquantel Spot-on (Broadline®) against Ixodes ricinus (Linné, 1758) on Cats.

Speed of kill, repellent (anti-feeding) and acaricidal efficacy of an imidacloprid 10 % (w/w) /flumethrin 4.5 % (w/w) collar (Seresto(®), Bayer) and a spot-on formulation of fipronil 8.3 % (w/v) /(S)-methoprene 10 % (w/v) /eprinomectin 0.4 % (w/v) /praziquantel 8.3 % (w/v) (Broadline(®), Merial) against artificiallyinduced infestations with Ixodes ricinus on cats, were assessed in a parallel group design, randomised, controlled study. Twenty-four cats were included and randomly allocated to treatment groups or a non-treated control group. Starting on Day (D) 7 after treatment until D28, cats were each infested with 50 I. ricinus at weekly intervals. Ticks were counted in situ on the cats at 6, 12 and 24 h and upon removal 48 h after each infestation. Based on arithmetic means, Seresto(®) proved to be 100 % effective against adult I. ricinus at all assessment times (6, 12, 24 and 48 h after infestation) throughout the month-long study. Broadline(®) was 0 % to 16.7 % effective at 6 h, 26.8 % to 50.0 % effective at 12 h, while at 24 h after infestation efficacy peaked at 81.5 % on D15 declining to 31.5 % on D29. Based on the 48 h tick counts, the efficacy of Broadline(®) peaked at 100 % on D16 after treatment and decreased to 83.2 % by D30. The Seresto(®) collar provided significantly faster speed of kill and better persistent acaricidal effectiveness against Ixodes ricinus on cats compared to Broadline(®) spot-on. The additional repellent (anti-feeding) effect of Seresto(®) prevents parasites from taking a blood meal and thereby reduces the risk of vector-borne disease pathogen transmission.

Imidacloprid 10 % / flumethrin 4.5 % collars (Seresto®, Bayer) successfully prevent long-term transmission of Ehrlichia canis by infected Rhipicephalus sanguineus ticks to dogs.

The objective of this study was to determine the empirical efficacy of imidacloprid 10 %/flumethrin 4.5 % (Seresto®) collars in preventing long-term transmission of Ehrlichia canis by infected Rhipicephalus sanguineus ticks to dogs. The study was a parallel group design, single centre, randomised, non-blinded, controlled, long-term efficacy study. The treatment group of 8 dogs was fitted with Seresto® collars, the untreated control group of 8 dogs received no collars. Ehrlichia canis-infected ticks were released into the dogs sleeping quarters at 14-day intervals up to Day +378. Control group dogs infected with E. canis were continuously replaced to keep the control sample size constant, and a total of 39 control dogs were required. The final clinical examination and blood sampling occurred on Day +420. The primary assessment criterion was the number of dogs infected with E. canis, as confirmed by IFA and PCR, and the secondary criterion was the acaricidal efficacy based on tick counts. All scheduled blood samples taken were subject to analyses for both PCR and IFA, but only positive cases are discussed. Up to Day +378, none of the collar-treated dogs were infected with E. canis, whereas 34 of the 35 untreated dogs enrolled before Day +371 were infected. The acaricidal efficacy of the collar ranged from 90 % to 100 % for the duration of the assessment period.

Prophylactic treatment of flea-infested dogs with an imidacloprid / flumethrin collar (Seresto®, Bayer) to preempt infection with Dipylidium caninum.

The objective of the study was to determine the sustained effectiveness of 10 % imidacloprid and 4.5 % flumethrin, incorporated in a slow-release matrix collar, in preventing Dipylidium caninum infection in dogs after repeated laboratory infestations with fleas infected with metacestodes of this tapeworm. Efficacy against infection with D. caninum was evaluated by infesting 16 dogs with cat fleas (Ctenocephalides felis) on study days 7, 14, 21, 28, 35 and 42, from batches suitably infected with D. caninum metacestodes. Prior to each post-treatment infestation the D. caninum infection rate for the fleas was determined by microscopically examining 100 fleas for D. caninum metacestodes. The D. caninum prevalence in the fleas used for infestations ranged from 23 % to 52 %. Medicated collars were fitted to 8 of the dogs on study day 0. The weight of the IVP collars varied between 35.48 g and 38.48 g (average 37.16 g), whilst animal weight varied between 12.20 kg and 17.98 kg (treated group, n = 8, average 14.79 kg). Seven days later infestation of each of the 16 dogs with 250 fleas commenced. Infestations continued at weekly intervals until Day 42 with efficacy against fleas evaluated 24 hours after each infestation. From Days 21 to 74, infection of the dogs with D. caninum was verified (daily examination of faeces and cages for the presence of expelled proglottids). Calculation of prophylactic effectiveness of the collars in preventing infection with D. caninum was based on the difference in geometric mean numbers of scoleces between groups at necropsy on Day 75. Effective prevention of infection with D. caninum was found to be 96.6 %. Efficacy of the collars against fleas was ≥ 99.9 % for the duration of the assessment period. Newly acquired infestations of fleas are rapidly eliminated by the insecticidal components of the medicated collars over a period of several months. In the event of fleas being infected with metacestodes, with D. caninum can be prevented in collared dogs, concurrently reducing the likelihood of transmission to humans.

Efficacy of a novel fipronil spot-on for the treatment and control of induced infestations of adult cat fleas (Ctenocephalides felis) and castor bean ticks (Ixodes ricinus) on cats.

Cat fleas (Ctenocephalides felis) and the castor bean tick (Ixodes ricinus) cause discomfort and health effects due to bites and ingestion of blood and they serve as vectors for several animal and human pathogens. Effectiveness of a novel 10 % w/v fipronil spot-on (Eliminall®/Exproline vet™, marketed by Pfizer Animal Health and registered and manufactured by Krka, d.d., Novo mesto) was confirmed against these parasites on experimentally infested cats. Two parallel, unicentre and masked controlled studies were conducted with European mixed breed and mixed sex cats. Cats were allocated randomly to one of two treatment groups based on either pre-treatment flea counts (study 1) or pre-treatment tick counts (study 2). In each of the study, eight animals served as control, while another eight animals were treated once topically with the unit label dose of 50 mg fipronil per cat (10.6-23.8 mg/kg). At each reinfestation, animals were infested with approximately 100 fleas or 60 ticks to achieve adequate infestation rates. Parasites were removed and counted on days 2, 9, 16, 23, 30 and 37, 48 h after the treatment or experimental infestation. Excellent effectiveness was demonstrated on day 2 (100 and 94 % efficacy against fleas and ticks, respectively) and lasted for up to 5 weeks (efficacy ≥96 %) against fleas and up to 4 weeks against ticks (efficacy ≥94 %). The product was well tolerated and no adverse reactions were observed.

The effects of a pour-on formulation of fluazuron 2.5 % and flumethrin 1 % on populations of Rhipicephalus decoloratus and Rhipicephalus microplus both on and off bovine (Bonsmara breed) hosts.

The present study demonstrated the efficacy of a pour-on formulation of fluazuron 2.5 % and flumethrin 1 % (Drastic Deadline eXtreme®) against Rhipicephalus decoloratus and Rhipicephalus microplus on cattle on pasture previously grazed by experimentally infested animals. Six tick-free cattle were placed on the pasture and treated 7 days later (Day 0) with the pour-on. They were retreated on Days 63, 126 and 189 and monthly tick counts were done. Mean numbers of adult R. decoloratus and/or R. microplus decreased from 53 and 14 on Days 56 and 112 respectively to 2 or less on all other occasions including Day 254. Compared to the numbers of R. decoloratus and/or R. microplus larvae collected from vegetation in the previous year, larval numbers declined by 40.7 % on Day 28, and thereafter reduction remained between 84 % and 100 %. Pairs of tracer calves placed on the pasture for 7 days each month were then held in pens and adult ticks that detached collected. Reduction in the numbers of R. decoloratus collected from tracer animals was 75 % on Day 56 and remained above 93 % except for Day 224 when it temporarily decreased to 78.5 %. Reduction in the numbers of R. microplus was 97.5 % on Day 28 and remained above 98 % until the conclusion of the study on Day 254. Treatment with the pour-on formulation of fluazuron and flumethrin resulted in a marked decrease in the numbers of R. decoloratus and/or R. microplus on treated cattle followed by a reduction in the numbers of larvae questing on the vegetation and ticks picked up by tracer calves. No other potential host species for R. decoloratus and/or R. microplus were present in the camps.

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for studies evaluating the efficacy of parasiticides in reducing the risk of vector-borne pathogen transmission in dogs and cats.

These guidelines are intended to provide an in-depth review of current knowledge and assist the planning and implementation of studies for evaluating the efficacy of parasiticides in reducing transmission of vector-borne pathogens (VBPs) to dogs and cats. At present, the prevention of VBP transmission in companion animals is generally achieved through the administration of products that can repel or rapidly kill arthropods, thus preventing or interrupting feeding before transmission occurs. The present guidelines complement existing guidelines, which focus on efficacy assessment of parasiticides for the treatment, prevention and control of flea and tick infestations, but also give guidance for studies focused on other vectors (i.e. mosquitoes and phlebotomine sand flies). The efficacy of parasiticides in reducing VBP transmission can be evaluated through laboratory or field studies. As such, the present guidelines provide recommendations for these studies, representing a tool for researchers, pharmaceutical companies and authorities involved in the research, development and registration of products with claims for reducing VBP transmission in dogs and cats, respecting the overall principles of the 3Rs (replacement, reduction and refinement). Gaps in our current understanding of VBP transmission times are herein highlighted and the need for further basic research on related topics is briefly discussed.

Comparative efficacy and safety of two treatment regimens with a topically applied combination of imidacloprid and moxidectin (Advocate) against generalised demodicosis in dogs.

This laboratory study compared the efficacy of two treatment regimens using an imidacloprid (10%)/moxidectin (2.5%) topical formulation (Advocate, Bayer) on dogs with generalised demodicosis. Sixteen dogs were randomly allocated to two equal groups. One group was treated at 28-day intervals for 12 weeks and the second group at weekly intervals for 15 weeks. Mite numbers were estimated and demodectic lesions were evaluated on each dog before treatment and at approximately 28-day intervals thereafter. Consistently greater reduction in mite numbers was recorded for the weekly treatment regimen. Dogs treated at weekly intervals exhibited markedly fewer clinical signs and greater hair regrowth and weight gain than those treated at 28-day intervals. To assess the safety of a weekly treatment interval in dogs, a study was done in which the investigational compound was administered at weekly intervals at five times the recommended dose for a period of 16 consecutive weeks. Apart from transient erythema at the site of administration in one dog and scaliness of the skin in another, no clinical signs of toxicity could be observed. Assessment of 27 blood parameters indicated that only basophils were outside the reference values on days +13 and +69, during the safety trial period.

Efficacy of topically administered fluralaner or imidacloprid/moxidectin on dogs with generalised demodicosis.

BACKGROUND: Canine demodicosis is classified as localised or generalised according to the extent of the disease. Chronic generalised demodicosis is a difficult skin disease to treat and unlikely to resolve without therapy. This laboratory study compared the efficacy of two topical spot-on medications, fluralaner or a combination of imidacloprid and moxidectin, against naturally acquired generalised demodicosis in dogs. METHODS: Sixteen client-owned dogs with naturally acquired generalised demodicosis were randomly allocated to 1 of 2 study groups consisting of 8 dogs each. On Day 0, dogs in 1 group were treated once with fluralaner spot-on solution. Dogs in the other group were treated with the imidacloprid/moxidectin spot-on solution on 3 occasions (Days 0, 28 and 56) or weekly in severe cases. Mites were counted in skin scrapings and demodectic lesions were evaluated on each dog before treatment, and at 28-day intervals over the 12-week period. Deep skin scrapings were made from the same 5 sites on each dog at each examination. RESULTS: After administration of fluralaner, miticidal efficacy was 99.7% at Day 28, > 99.9% at Day 56 and 100% at Day 84. Efficacy in dogs treated topically with the imidacloprid and moxidectin combination, was 9.8% at Day 28, 45.4% at Day 56 and 0% at Day 84, and was significantly (P < 0.01) lower than the fluralaner treated group at each post-treatment time point. CONCLUSIONS: A single topical administration of fluralaner eliminated Demodex sp. mites on dogs with generalised demodicosis. Topical imidacloprid/moxidectin combination treatment administered 3 times at 28-day intervals, or more frequently, did not eliminate mites from most treated dogs.

Immediate and persistent efficacy of sarolaner (Simparica™) against Haemaphysalis elliptica on dogs.

BACKGROUND: The southern African yellow dog tick, Haemaphysalis elliptica, occurs in eastern and southern Africa and adults infest domestic and wild carnivores. This tick species is also a vector of the highly virulent Babesia rossi pathogen, the causative agent of canine babesiosis in sub-Saharan Africa. Sustained high levels of efficacy of a parasiticide are not only important in protecting dogs against the direct effects of tick infestation, but also in reducing the risk of tick-borne diseases. Sarolaner (Simparica™ chewable tablets) has been reported to be effective against the major tick species infesting dogs in Europe and the USA, including representatives from the genera Amblyomma, Ixodes, Rhipicephalus and Dermacentor. Until now no efficacy evaluations have been reported against species of the genus Haemaphysalis. The objective of the study was to confirm the efficacy of a single 2 mg sarolaner/kg oral dose of Simparica™ against induced infestations with H. (R.) elliptica, an important parasite of dogs in southern Africa. METHODS: This blinded, randomised, single centre, placebo controlled efficacy study followed a parallel group design and was conducted on two groups consisting of eight purpose-bred dogs each. Animals were treated orally, once on Day 0, with either a placebo compound (Group 1) or Simparica™ (Group 2). Simparica™ was administered orally at a dose rate of 2 mg sarolaner/kg body weight. The dogs were infested with ticks on Days - 7, - 2, 5, 12, 19, 26 and 33, with removal counts conducted on Days - 5, 2, 7, 14, 21, 28 and 35. RESULTS: A single oral administration of Simparica™ (sarolaner) at a minimum dose of 2 mg/kg resulted in a 100% efficacy against existing infestations of H. (R.) elliptica on dogs and a 100% reduction in live ticks following weekly re-infestations for 35 days. Moreover, the immediate and persistent high levels of efficacy observed in this study for 35 days is consistent with those observed in previous studies against ticks in other genera. CONCLUSIONS: The efficacy of sarolaner (Simparica™), administered orally to dogs at the minimum label dose of 2.0 mg/kg, was demonstrated against existing and weekly re-infestations of H. (R.) elliptica for at least 5 weeks. Efficacy of 100% was achieved against existing infestations as well as weekly re-infestations.

A study on the long-term efficacy of Seresto® collars in preventing Babesia canis (Piana & Galli-Valerio, 1895) transmission to dogs by infected Dermacentor reticulatus (Fabricius, 1794) ticks.

BACKGROUND: An imidacloprid/flumethrin collar (Seresto®) was previously shown to prevent infection with Babesia canis, transmitted by Dermacentor reticulatus, in dogs for up to 1 month after application. The present study evaluated the prevention of transmission throughout the claimed efficacy period of 8 months. METHODS: Eight animals each were randomly included in groups 1 (negative control) and 2 (Seresto® collar), respectively. Animals in group 2 received the Seresto® collar on Day 0. Tick challenges were performed monthly from the 2nd to the 8th month. Assessment criteria included in situ tick counts 48 hours post-challenge, polymerase chain reaction (PCR) analyses and immunofluorescence assays (IFA). Whenever dogs were diagnosed with babesiosis they were "rescue-treated", excluded and replaced. Consequently, 24 replacement animals were introduced at various time points throughout the study in the control group; thus data for a total of 32 dogs were available in the latter group at study termination. RESULTS: Acaricidal efficacy for in situ counts was 93% on Day 30, and ranged from 97 to 100% thereafter. No B. canis specific DNA or antibodies were detected in any Seresto®-treated dog at any time. Babesia canis-specific DNA and antibodies were detected in 2-6 of 8 control dogs after each challenge, confirming the validity of the challenge model. CONCLUSIONS: The Seresto® collar was highly effective against challenges with D. reticulatus ticks for up to 8 months. The high sustained acaricidal efficacy over this period prevented transmission of B. canis, thus fully protecting dogs against infection in this experimental infestation model.

Transmission of Anaplasma phagocytophilum (Foggie, 1949) by Ixodes ricinus (Linnaeus, 1758) ticks feeding on dogs and artificial membranes.

BACKGROUND: The interplay of speed of activity of acaricidal products and tick-borne pathogen transmission time is the major driver for disease prevention. This study aimed to investigate the time required for transmission of Anaplasma phagocytophilum by adult Ixodes ricinus ticks in vivo on dogs, and to confirm the time required for transmission observed in vivo, in vitro. METHODS: Nymphs of I. ricinus were experimentally infected with an A. phagocytophilum strain of canine origin. Dogs were allocated to 6 groups of 3 dogs each. Groups 1-5 were infested with 50 A. phagocytophilum-infected female adult ticks on Day 0. Ticks were removed post-infestation at 3, 6, 12, 24 and 48 h. Dogs in Group 6 were infested with 60 A. phagocytophilum-infected female adult ticks (left on dogs until engorged). Dogs were observed daily for general health and clinically examined on Day 0, and weekly from Day 14. Blood was collected for qPCR and serological analysis on Day 0 (pre-challenge) and weekly thereafter. In the in vitro study each artificial feeding chamber was seeded with 10 adult ticks (5 male/5 female), attachment assessed, and blood pools sampled for qPCR at 6 h intervals up to 72 h after first tick attachment. RESULTS: Anaplasma phagocytophilum specific antibodies and DNA were detected in all 3 dogs in Group 6. No A. phagocytophilum-specific antibodies or DNA were detected in any dogs in Groups 1-5. All dogs remained healthy. Female tick attachment in 60 artificial feeding chambers over 72 h ranged between 20-60%. Anaplasma phagocytophilum DNA was detected in the blood collected from 5% of chambers sampled at 6 h, with the highest number of positive samples (16.3%) observed at 36 h. CONCLUSIONS: Transmission of A. phagocytophilum by I. ricinus ticks starts within a few hours after attachment but establishment of infections in dogs is apparently dependent on a minimum inoculation dose that was only observed when ticks attached for greater than 48 h. These findings highlight the need for acaricidal products to exert a repellent and/or rapid killing effect on ticks to forestall transmission and subsequent disease.

Knock-down and speed of kill of a combination of fipronil and permethrin for the prevention of Ctenocephalides felis flea infestation in dogs.

BACKGROUND: A topical combination of fipronil + permethrin (Frontline Tri-Act/Frontect, Merial) has recently been developed to control fleas, ticks, mosquitoes, sandflies and stable flies on dogs. Two studies were conducted to assess its speed of kill and knock-down effect on Ctenocephalides felis fleas. The combination was compared to either fipronil alone or to a combination of permethrin, dinotefuran, and pyriproxyfen, METHODS: In each study, 18 dogs were randomly allocated to one of three groups: (Group 1: untreated dog; Group 2: treated once on D0 with the combination of fipronil and permethrin; Group 3: treated once on D0 either with fipronil alone (study 1) or with a combination of permethrin, dinetofuran and pyriproxyfen (study 2)). Each dog was infested with 100 unfed adult C. felis fleas on Days 2 (study 2), 7, 14, 21 and 28. Fleas were collected from dogs at 1 h and 12 h post- infestations (PI) (study 1) or at 2 h and 6 h PI (study 2) to assess efficacy and from collection pans underneath cages 1 h (study 1) or 5 min (study 2) PI to assess knock-down effect. RESULTS: All treated dogs had significantly (p ≤ 0.01) lower flea counts than untreated dogs at every time point in both studies. For a whole month, a significant knock-down effect against infesting fleas is obtained in five minutes PI with the combination of permethrin and fipronil. Complete efficacy (>95%) was achieved in 1 h (study 1) or 2 h (study 2) PI for 14 days and by 6 h PI for all challenges conducted throughout the month. Efficacy remains >85% at 2 h PI for the whole month. A significantly higher efficacy of the fipronil + permethrin combination compared to other treatments was demonstrated at the earliest time points for the month (1 h knock-down effect and insecticidal efficacy compared to fipronil alone; 5 min knock-down effect compared to the combination of permethrin + dinetofuran + pyriproxyfen). CONCLUSIONS: The rapid flea knock-down effect and speed of kill demonstrated by the spot on combination of fipronil + permethrin provide a reliable strategy against flea infestations in dogs.

Efficacy and speed of kill of a topically applied formulation of dinotefuran-permethrin-pyriproxyfen against weekly tick infestations with Rhipicephalus sanguineus (sensu lato) on dogs.

BACKGROUND: Rhipicephalus sanguineus (sensu lato) is a vector of canine babesiosis, anaplasmosis and ehrlichiosis. In order to reduce the chance of transmission of these diseases, an ectoparasiticide should rapidly repel or kill new infestations with this tick. The primary objective of the present study was to evaluate the treatment and preventive acaricidal efficacy of Vectra® 3D (54.45 mg/ml of dinotefuran, 396.88 mg/ml of permethrin and 4.84 mg/ml of pyriproxyfen) against R. sanguineus (s.l.) measured at 2, 8, and 48 h after treatment and weekly re-infestation. METHODS: Twenty-four dogs were each infested with 50 adult R. sanguineus (s.l.) on Day -7 and allocated to three groups (n = 8) based on tick counts: an untreated control group (Group 1), and two groups (Groups 2 and 3) treated with Vectra®3D. The dogs in each group were infested with 50 ticks on Day -2. Vectra®3D was administered topically to the dogs on Day 0. Ticks were counted, in situ at 2 and 8 h after treatment on dogs in Groups 1 and 3. Group 3 was then withdrawn from the study and ticks were counted and removed from the dogs in Groups 1 and 2, 48 h after treatment. On Days 7, 14, 21, 28, 35 and 42, the dogs in Groups 1 and 2 were re-infested with 50 ticks, which were then counted in situ at 2 and 8 h, and counted and removed at 48 h after re-infestation. RESULTS: Ticks from the initial infestation were visually unaffected by 2 and 8 h after treatment. However, by 2 h after weekly re-infestation the arithmetic mean (AM) efficacy of Vectra® 3D from Days 7 through 28 ranged from 61.1 to 78.8 %, falling to 60.1 and 47.4 % on Days 35 and 42 respectively. By 8 h after weekly re-infestation, the AM efficacy ranged from 89.1 to 97.4 % falling to 81.4 and 69.8 % on Days 35 and 42 respectively. The AM efficacy 48 h after treatment after the initial infestation was 22.9 % but after weekly re-infestation the efficacy at 48 h ranged from 89.1 to 100.0 %, falling to 86.0 and 81.1 % on Days 35 and 42 respectively. CONCLUSION: Vectra® 3D demonstrated significant efficacy against new infestations of adult R. sanguineus (s.l.) ticks within 2 h of infestation as compared to the untreated control group and achieved over 89.1 % efficacy within 8 h of infestation for up to 4 weeks after administration. These results indicate that Vectra® 3D has a rapid and significant efficacy against new infestations of adult R. sanguineus (s.l.) ticks and should therefore be considered as part of a strategy against important vector-borne diseases in dogs.

Comparative efficacy of oral administrated afoxolaner (NexGard™) and fluralaner (Bravecto™) with topically applied permethrin/imidacloprid (Advantix(®)) against transmission of Ehrlichia canis by infected Rhipicephalus sanguineus ticks to dogs.

BACKGROUND: The ability of the topical spot-on Advantix(®) (50 % permethrin/10 % imidacloprid) to prevent transmission of Ehrlichia canis by infected Rhipicephalus sanguineus ticks to dogs has previously been reported. The recent market introduction of chewable tablets containing the novel compounds, afoxolaner (NexGard™) and fluralaner (Bravecto™) enabled us to conduct a comparative efficacy study with respect to the ability of these three products to block transmission of E. canis by ticks to dogs. The speed of kill, immediate drop-off rate and anti-attachment efficacy of the respective products were also studied. METHODS: The study was a blinded parallel group design, wherein 32 dogs were randomised into four different groups of eight dogs. Group 1 served as negative placebo control, group 2 and 3 were treated on Days 0, 28 and 56 with NexGard™ and Advantix(®), respectively. Group 4 was dosed once on Day 0 with Bravecto™. For tick efficacy assessments 50 non-infected ticks were placed onto the dogs on Days 30, 35, 42, 49, 56, 63, 70, 77 and 84 and on animal tick counts were performed at 3 h, 6 h and 12 h after infestation. To evaluate the ability to block transmission of E. canis, each dog was challenged by releasing 80 adult E. canis-infected R. sanguineus ticks into their sleeping kennels on Days 31, 38, 45 and 52. The animals were monitored for clinical signs of monocytic ehrlichiosis (pyrexia and thrombocytopenia) and were tested for E. canis DNA by PCR and for specific antibodies using IFA. A dog was considered infected with E. canis if both PCR and IFA yielded positive test results up to Day 84. RESULTS: Mean arithmetic tick counts on dogs treated with the Advantix(®) spot-on were significantly (P < 0.0005) lower throughout the study as compared with the negative controls and was, with respect to the speed of kill and resulting onset of acaricidal efficacy, superior over NexGard™ and Bravecto™ at all time points in the 12 h period observed (3 h, 6 h and 12 h). None of the dogs treated with the Advantix(®) spot-on became infected with E. canis, whereas six out of eight untreated control dogs acquired the infection. Furthermore, E. canis infection was diagnosed in four out of eight dogs treated with NexGard™ and in two out of eight dogs treated with Bravecto™. CONCLUSIONS: The speed of kill of the two recently registered systemic compounds against R. sanguineus was not sufficiently fast to prevent transmission of E. canis and resulted in only low partial blocking and protection capacity while Advantix(®) effectively blocked transmission of E. canis to dogs in the challenge period and thus provided adequate protection for dogs against monocytic ehrlichiosis.

Efficacy of sarolaner, a novel oral isoxazoline, against two common mite infestations in dogs: Demodex spp. and Otodectes cynotis.

The efficacy of sarolaner (Simparica™, Zoetis) was evaluated against Demodex spp. in dogs with generalized demodicosis and against Otodectes cynotis (otodectic mange) in dogs with induced infestations. In the first study, 16 dogs with clinical signs of generalized demodicosis and positive for Demodex spp. mites were randomly assigned to treatment with either sarolaner (2mg/kg) orally on Days 0, 30 and 60, or topical imidacloprid (10mg/kg) plus moxidectin (2.5mg/kg) solution every 7 days from Day 0 to Day 81. For sarolaner-treated dogs, pretreatment mite counts were reduced by 97.1% at 14days and 99.8% by 29 days after the first dose, with no live mites detected thereafter. Weekly imidacloprid plus moxidectin resulted in 84.4 and 95.6% reduction at these two time points, respectively, with no mites detected from Day 74 on. All dogs in both groups showed marked improvement in the clinical signs of demodicosis. In the second study, 32 dogs with induced infestations of O. cynotis were randomly assigned (eight per group) to oral sarolaner (2mg/kg) as a single treatment on Day 0 or as a two dose regime (Days 0 and 30), or a placebo group for each of the dose regimes. Sarolaner administered at 2mg/kg as a single oral dose resulted in a 98.2% reduction at Day 30 and two doses of sarolaner, administered one month apart, resulted in a 99.5% reduction in ear mites at Day 60 compared to placebo controls. There were no treatment related adverse events in either study. In these studies, sarolaner at an oral dose of 2mg/kg was highly effective in reducing the live mite counts associated with a natural infestation of Demodex spp. and an induced infestation of O. cynotis. In addition, the Demodex-infested dogs showed a marked improvement in the clinical signs of generalized demodicosis.

Efficacy and safety of a novel oral isoxazoline, sarolaner (Simparica™), for the treatment of sarcoptic mange in dogs.

The efficacy of the novel isoxazoline, sarolaner (Simparica™) was investigated in dogs with clinical signs consistent with sarcoptic mange and harbouring natural infestations of Sarcoptes scabiei. One placebo-controlled laboratory study and one multi-centred field study with a commercial comparator containing imidacloprid/moxidectin (Advocate(®) spot-on) were conducted. Oral or topical treatments were administered on Days 0 and 30. Up to 10 skin scrapings were taken for the assessment of S. scabiei infestations from each dog before treatment and on Days 14, 30, 44 and 60 in the laboratory study, and on Days 30 and 60 in the field study. In the laboratory study, efficacy was calculated based on the percent reduction of mean live mite counts compared to the placebo group. In the field study parasitological cure rate (% dogs free of mites) was determined and non-inferiority of sarolaner to the control product was assessed. In the laboratory study 44 mixed breed dogs were enrolled in four batches. Due to decreasing mite counts in the placebo treated dogs, immunosuppression with dexamethasone (0.4mg/kg three times per week for two weeks) was initiated in all dogs on study at that time (n=6) and those subsequently enrolled (n=14). In the field study, dogs were enrolled in a 2:1 ratio (sarolaner:comparator); 79 dogs were assessed for efficacy and safety, and an additional 45 dogs were assessed for safety only. There were no treatment related adverse events in either study. In the laboratory study, no mites were found on any sarolaner-treated dogs 14 days after the first treatment except for one dog that had a single mite on Day 44. In the field study, the parasitological cure rate was 88.7% and 100% in the sarolaner group and 84.6% and 96.0% in the imidacloprid/moxidectin group, on Days 30 and 60, respectively. Statistical analysis showed that sarolaner was non-inferior to imidacloprid/moxidectin at both time points. The clinical signs of sarcoptic mange, including hair loss, papules, pruritus, erythema, and scaling/crusting improved throughout the study. Sarolaner was safe, achieved 100% reduction in the numbers of S. scabiei detected and resulted in marked improvement of the clinical signs of sarcoptic mange in dogs following two monthly oral administrations.

Determination of the effective dose of a novel oral formulation of sarolaner (Simparica™) for the treatment and month-long control of fleas and ticks on dogs.

Three laboratory studies were conducted to determine the appropriate dose of sarolaner, a novel isoxazoline, for the treatment and month-long control of infestations of fleas and ticks on dogs. In the first study, dogs were treated orally with sarolaner suspension formulations at 1.25, 2.5 or 5.0mg/kg, and infested with Dermacentor reticulatus, Rhipicephalus sanguineus ticks and with Ctenocephalides felis felis (cat flea) prior to treatment and then weekly for up to 8 weeks. Fleas and ticks were counted 48h after treatment and after each subsequent infestation at 24h for fleas and 48h for ticks. The lowest dose of sarolaner (1.25mg/kg) provided 100% efficacy against fleas from treatment through Day 35 and 98.4% at Day 56. This dose of sarolaner resulted in 99.7-100% control of both species of ticks through Day 28. In Study 2, dogs were dosed orally with placebo or sarolaner suspension formulations at 0.625, 1.25 or 2.5mg/kg and infested with Ixodes scapularis prior to treatment and weekly for 6 weeks, Amblyomma americanum (pretreatment and Day 26), Dermacentor variabilis (Day 33) and A. maculatum (Day 41). Ixodes scapularis was the most susceptible; the lowest dose (0.625mg/kg) providing>95% efficacy through Day 43. Efficacy against D. variabilis on Day 35 was>95% at 1.25 and 2.5mg/kg, whereas the 0.625mg/kg dose gave only 61.4% efficacy. Amblyomma spp. were the least susceptible ticks; efficacy of the 1.25mg/kg dose at Day 28 for A. americanum was markedly lower (88.5%) than achieved for D. reticulatus (100%) at Day 28 and also lower than for D. variabilis at Day 35 (96.2%). In Study 3, dogs were dosed orally with placebo or sarolaner in the proposed commercial tablet (Simparica™) at 1.0, 2.0 or 4.0mg/kg, and infested with A. maculatum, one of the ticks determined to be dose limiting, prior to treatment and then weekly for 5 weeks. All doses gave 100% control of the existing infestation. The two highest dosages resulted in >93% control of subsequent challenges for 5 weeks. There was no significant improvement in efficacy provided by the 4.0 mg/kg dose over the 2.0mg/kg dose (P>0.05) at any time point. The 2.0mg/kg dose was superior to the 1.0mg/kg on Day 14 (P=0.0086) and as efficacy for 1.0mg/kg declined below 90% at Day 28, a single 1mg/kg dose would not provide a full month of tick control. Thus, 2.0mg/kg was selected as the sarolaner dose rate to provide flea and tick control for at least one month following a single oral treatment.