The speed of kill of fluralaner (Bravecto™) against Ixodes ricinus ticks on dogs

Pharmacological studies and pharmacokinetic modelling to support the development of interventions targeting ecological reservoirs of Lyme disease

The development of interventions targeting reservoirs of Borrelia burgdorferi sensu stricto with acaricide to reduce the density of infected ticks faces numerous challenges imposed by ecological and operational limits. In this study, the pharmacokinetics, efficacy and toxicology of fluralaner were investigated in Mus musculus and Peromyscus leucopus mice, the main reservoir of B. burgdorferi in North America. Fluralaner showed rapid distribution and elimination, leading to fast plasma concentration (Cp) depletion in the first hours after administration followed by a slow elimination rate for several weeks, resulting in a long terminal half-life. Efficacy fell below 100% while Cp (± standard deviation) decreased from 196 ± 54 to 119 ± 62 ng/mL. These experimental results were then used in simulations of fluralaner treatment for a duration equivalent to the active period of Ixodes scapularis larvae and nymphs. Simulations showed that doses as low as 10 mg/kg have the potential to protect P. leucopus against infestation for a full I. scapularis active season if administered at least once every 7 days. This study shows that investigating the pharmacology of candidate acaricides in combination with pharmacokinetic simulations can provide important information to support the development of effective interventions targeting ecological reservoirs of Lyme disease. It therefore represents a critical step that may help surpass limits inherent to the development of these interventions.

Comparison of the initial and residual speed of Ixodes scapularis kill on dogs treated with a single dose of Bravecto® Chew (25 mg/kg fluralaner) or Simparica TRIO® (1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel)

BACKGROUND

Compliant ectoparasiticide product use is a comprehensive way to control ticks and reduce the risk of tick-borne pathogen transmission to dogs. Because the systemically acting isoxazoline ectoparasiticides require tick attachment for drug delivery, fast speed of kill is essential to minimize tick-borne pathogen transmission risk.

METHODS

Dogs of satisfactory tick-carrying capacity were randomly allocated to treatment groups and administered, per label instructions, Bravecto® Chews (minimum 25 mg/kg fluralaner), Simparica TRIO® (minimum 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, 5 mg/kg pyrantel), or no treatment. Dogs were infested with approximately 50 unfed adult (35 female, 15 male) Ixodes scapularis on Day -2, 21 and 28. Live tick counts were performed at 4, 8, 12 and 24 h post-treatment (Day 0) and post-infestation on Day 21 and 28. Tick control efficacy was determined by comparing live tick means for each product-treated group to the untreated control group and each other at all time points using a linear mixed model. The percent of dogs free of live ticks was analyzed using the Fisher's exact test for treatment group comparison.

RESULTS

The untreated control group maintained adequate tick infestations throughout the study. Using geometric means, an existing I. scapularis infestation was controlled by 99.7% and 93.0% 12 h post-treatment and by 100% and 99.5% 24 h post-treatment, for Bravecto® and Simparica TRIO®-treated dogs, respectively. Ixodes scapularis infestations were controlled more quickly for Bravecto®- compared to Simparica TRIO®-treated dogs on Day 21 at 8 h (efficacy 74.0% vs. 0.0%, p = 0.003) and 12 h (efficacy 99.2% vs. 39.4%, p < 0.001) post-infestation and Day 28 at 8 h (efficacy 92.2% vs. 0.0%, p < 0.001) and 12 h (efficacy 99.6% vs. 27.7%, p < 0.001) post-infestation. On Day 28 post-treatment, the efficacy of Bravecto® and Simparica TRIO® to control a new I. scapularis infestation was 100% and 96.6%, respectively, by 24 h post-infestation. Of product-treated dogs, 100% of Bravecto®-treated dogs were free of live ticks by 24 h post-treatment or post-infestation. No treatment-related adverse reactions occurred during the study.

CONCLUSIONS

Ixodes scapularis infestations are controlled more quickly 21 and 28 days post-treatment for dogs administered a single dose of Bravecto® compared to dogs administered a single dose of Simparica TRIO®.

Treatment of dogs with Bravecto® (fluralaner) reduces mosquito survival and fecundity

BACKGROUND

Mosquitoes serve as the vector of canine heartworm (Dirofilaria immitis), which represents a significant and persistent threat to canine health. A reduction in the longevity and/or reproductive success of mosquitoes that take a blood meal from fluralaner-treated dogs may consequently reduce the local transmission of heartworm and prevent new infections. A novel secondary effect of an oral formulation of the ectoparasiticide fluralaner (Bravecto®) against a laboratory strain of the mosquito Aedes aegypti, a potential major vector of canine heartworm, was investigated in this study.

METHODS

Six dogs were administered a single dose of fluralaner orally in the form of Bravecto® Chews (at the labeled fluralaner dose of 25 mg/kg body weight), while six control dogs received no treatment. Mosquitoes were fed on blood that was collected from each dog prior to treatment and weekly for 15 weeks post-treatment to assess the continued effects of fluralaner as its serum level decreased. Mosquito fitness was assessed by three parameters: rate of successful blood-feeding, survival, and egg laying.

RESULTS

Successful blood-feeding rate was similar between control and treatment groups. In the fluralaner treatment, mosquito survival was significantly reduced within the first 24 h after blood-feeding, for the first 12 weeks post-treatment of the dogs (efficacy range = 33.2-73.3%). Survival of mosquitoes up until a potentially heartworm-infective timepoint (14 days post-blood-feeding) was significantly reduced in the fluralaner-treated group at several timepoints (1, 2, 5, 11, 12, 13, 14, and 15 weeks post-treatment; efficacy range = 49.4-91.4%), but was less consistently reduced at the other timepoints. Egg laying by mosquitoes was almost completely suppressed for the first 13 weeks following treatment of the dogs with fluralaner (treatment efficacy ≥ 99.8%).

CONCLUSIONS

Mosquitoes fed blood from fluralaner-treated dogs experienced a significant reduction in survival and fecundity. These findings support the potential for a reduction in heartworm transmission directly by lethal effects on the vector and indirectly through a reduction of the local vector population when mosquitoes are exposed to animals treated with fluralaner.

Survival and Fecundity of Anopheles stephensi and Anopheles albimanus Mosquitoes (Diptera: Culicidae) After Ingesting Bovine Blood Containing Various Veterinary Systemic Parasiticides

Systemic parasiticides in livestock can control zoophilic malaria vectors that contribute to residual malaria transmission. Membrane feeding techniques were used to screen seven systemic parasiticidic drugs currently in veterinary use for livestock and dogs. Drugs were tested in two laboratory strains of zoophilic Anopheles - A. stephensi (South Asian vector) and A. albimanus (Central American vector). To assess the relative potentials of these drugs, the resultant LC-50 for each drug was compared with what is known about the pharmacokinetic of the drug. Drugs with LC-50 values below the reported maximum plasma concentration of treated animals were considered as showing the most promise for use in the field. Ivermectin and fipronil showed the greatest promise for use in cattle against A. stephensi. Fipronil showed the greatest promise for use in cattle against A. albimanus. Both fluralaner and afoxolaner were highly effective against both mosquito species but pharmacokinetic data for these drugs in cattle are lacking. Eprinomectin, moxidectin and abamectin showed marginal to no promise for either mosquito species. At sublethal doses, ivermectin, fipronil, and afoxolaner (but not fluralaner) significantly reduced the larval production of surviving A. stephensi and A. albimanus. Further testing of candidate systemic parasiticides, including their product formulations, in livestock against field-collected populations of Anopheles is the next logical step toward full implementation of this strategy to manage zoophilic vectors.

Evaluation of fluralaner as an oral acaricide to reduce tick infestation in a wild rodent reservoir of Lyme disease

Background

Lyme disease (LD) is an increasing public health threat in temperate zones of the northern hemisphere, yet relatively few methods exist for reducing LD risk in endemic areas. Disrupting the LD transmission cycle in nature is a promising avenue for risk reduction. This experimental study evaluated the efficacy of fluralaner, a recent oral acaricide with a long duration of effect in dogs, for killing Ixodes scapularis ticks in Peromyscus maniculatus mice, a known wildlife reservoir for Borrelia burgdorferi in nature.

Methods

We assigned 87 mice to 3 fluralaner treatment groups (50 mg/kg, 12.5 mg/kg and untreated control) administered as a single oral treatment. Mice were then infested with 20 Ixodes scapularis larvae at 2, 28 and 45 days post-treatment and we measured efficacy as the proportion of infesting larvae that died within 48 h. At each infestation, blood from 3 mice in each treatment group was tested to obtain fluralaner plasma concentrations (C_p).

Results

Treatment with 50 mg/kg and 12.5 mg/kg fluralaner killed 97% and 94% of infesting larvae 2 days post-treatment, but no significant effect of treatment on feeding larvae was observed 28 and 45 days post-treatment. Mouse C_p did not differ significantly between the two tested doses. Mean C_p decreased from 13,000 ng/ml in the 50 mg/kg group and 4000 ng/ml in the 12.5 mg/kg group at Day 2 to < 100 ng/ml in both groups at Day 45.

Conclusions

We provide the first evidence that fluralaner is effective for killing immature ticks in Peromyscus mice, a first step in evaluating its potential for treating wild rodents as a public health intervention to reduce LD risk in endemic areas.

The effect of sublethal concentrations of deltamethrin and alphacypermethrin on the fecundity and development of Ixodes ricinus (Acari: Ixodidae) eggs and larvae

Two pyrethroids, deltamethrin (D) and alphacypermethrin (AC), have been used as commercial products for tick control worldwide. However, the effects of sublethal doses of these compounds on various tick species and their developmental stages have not been fully explored yet, although such knowledge could contribute to a more effective application of both pyrethroids and simultaneous reduction of their costs and undesirable side effects, including the harmful impact on other organisms and environmental contamination. This study investigates the effect of sublethal concentrations of D and AC applied to engorged females on the fecundity, development of eggs and larvae, and the number of offspring in the Ixodes ricinus (L.) tick, which is the most important vector of tick-borne diseases of humans in Europe. After detachment from rabbit's skin, fully engorged I. ricinus females were treated with 20 μl of pyrethroid solutions at five concentrations from 0.01562 to 0.25% and kept at 28 °C and 75% relative humidity. The impact of the pyrethroids on maturation and development of eggs as well as development of larvae was assessed based on parameters of the preoviposition and oviposition periods and the course of embryogenesis and egg hatch. The investigations have shown that both tested acaricides reduce the reproductive rate in I. ricinus females by inhibition of egg development and disturb embryonic development and larval hatch. Females did not lay eggs at concentrations higher than 0.0625% AC and 0.125% D. The lower concentrations of both pyrethroids disturbed or inhibited the embryogenesis and egg hatch in I. ricinus.

Efficacy of orally administered fluralaner in dogs against laboratory challenge with Haemaphysalis longicornis ticks

Background

Haemaphysalis longicornis ticks represent an ectoparasitic health threat to dogs. This study evaluated the immediate and persistent efficacy of orally administered fluralaner for control of this tick.

Methods

Twenty-four dogs were sorted into 4 groups based on their tick carrying capacity measured in a preliminary challenge. Two days before treatment, dogs were challenged with Haemaphysalis longicornis and then at the time of treatment dogs received with oral fluralaner at 10, 25 or 50 mg/kg respectively to 3 of the groups, while the remaining group was sham treated. Ticks were counted and categorized on all dogs 2 days after treatment (4 days after challenge). Tick challenges were repeated at 28, 56, 84 and 112 days following treatment with tick counts 48 hours following each challenge. Tick control efficacy was evaluated by comparing the mean (geometric) total live attached and dead engorged ticks on each fluralaner treated group with the sham treated dogs.

Results

Oral fluralaner is highly acaricidal for H. longicornis that feed on treated dogs. The mean efficacy rate in dogs treated with fluralaner at the commercial dose range of 25 to 50 mg/kg was greater than 90% at 114 days after treatment, whereas efficacy at this time in dogs treated at 10 mg/kg was 79%.

Conclusions

Fluralaner administered orally to dogs within the commercial dose range at 25 to 50 mg/kg is effective for up to 114 days against laboratory challenge with H. longicornis ticks.

A discovery and development roadmap for new endectocidal transmission-blocking agents in malaria

Reaching the overall goal of eliminating malaria requires halting disease transmission. One approach to blocking transmission is to prevent passage of the parasite to a mosquito, by preventing formation or transmission of gametocytes. An alternative approach, pioneered in the veterinary field, is to use endectocides, which are molecules that render vertebrate blood meals toxic for the mosquito vector, also killing the parasite. Field studies and modelling suggest that reducing the lifespan of the mosquito may significantly reduce transmission, given the lengthy maturation process of the parasite. To guide the development of new endectocides, or the reformulation of existing molecules, it is important to construct a framework of the required attributes, commonly called the target candidate profile. Here, using a combination of insights from current endectocides, mathematical models of the malaria transmission dynamics, and known impacts of vector control, a target candidate profile (TCP-6) and a regulatory strategy are proposed for a transmission reducing agent. The parameters chosen can be used to assess the potential of a new medicine, independent of whether it has classical endectocide activity, reduces the insect and parasite lifespan or any combination of all three, thereby constituting an ‘endectocidal transmission blocking’ paradigm.

A single topical fluralaner application to cats and to dogs controls fleas for 12 weeks in a simulated home environment

BACKGROUND

Fluralaner (Bravecto®, Merck Animal Health, Madison, NJ, USA) is a novel isoxazoline that provides up to 12 weeks flea and tick control when administered orally to dogs. Two assessor-blinded studies, one in dogs, the other in cats evaluated the sustained efficacy of a topical fluralaner formulation against fleas in a simulated home environment (SHE).

METHODS

Animals were ranked and blocked into groups of two using flea counts completed 24 hours following Ctenocephalides felis infestations placed on dogs on Day -64, and on cats on Day -36. Within blocks animals were randomized to a treatment group, 10 animals per group, one group to receive fluralaner spot-on (minimum dose rate for dogs, 25 mg/kg; for cats, 40 mg/kg), the other to be a sham-treated control. Animals were then placed into their SHE, one animal per pen or cage and then infested with 100 C. felis at weekly intervals. Dogs were infested from Day -56 through -21 and cats on Days -28 and -21. Fleas were counted and removed from each dog and cat on Day -1. Study animals were then held in clean pens/cages until treatment on Day 0. One day later, after treatment, all animals were returned to their home environment (SHE). Additional 50-flea challenges were placed on each animal on Days 22, 50 and 78. Fleas were counted and replaced on all animals on Day 1 and weekly thereafter for 12 weeks.

RESULTS

Arithmetic mean counts in control-group animals exceeded 10 fleas at all post-treatment assessments except on Days 1, 7 and 14. All control-group animals remained infested at each assessment from Day or 28 through Day 84, thereby validating the challenge methodology. Fluralaner efficacy was 100% on all occasions except for 2 fleas found on 1 dog on Day 1, and 3 fleas on 1 dog on Day 14. One flea was recovered from 1 fluralaner treated cat on Day 1. There were no treatment-related adverse events.

CONCLUSION

A single application of a topical formulation of fluralaner is well tolerated and highly effective in the prevention of flea infestations of dogs and cats throughout the 12 weeks following treatment.

The fungal alkaloid Okaramine-B activates an L-glutamate-gated chloride channel from Ixodes scapularis, a tick vector of Lyme disease

A novel L-glutamate-gated anion channel (IscaGluCl1) has been cloned from the black-legged tick, Ixodes scapularis, which transmits multiple pathogens including the agents of Lyme disease and human granulocytic anaplasmosis. When mRNA encoding IscaGluCl1 was expressed in Xenopus laevis oocytes, we detected robust 50-400 nA currents in response to 100 μM L-glutamate. Responses to L-glutamate were concentration-dependent (pEC₅₀ 3.64 ± 0.11). Ibotenate was a partial agonist on IscaGluCl1. We detected no response to 100 μM aspartate, quisqualate, kainate, AMPA or NMDA. Ivermectin at 1 μM activated IscaGluCl1, whereas picrotoxinin (pIC₅₀ 6.20 ± 0.04) and the phenylpyrazole fipronil (pIC₅₀ 6.90 ± 0.04) showed concentration-dependent block of the L-glutamate response. The indole alkaloid okaramine B, isolated from fermentation products of Penicillium simplicissimum (strain AK40) grown on okara pulp, activated IscaGluCl1 in a concentration-dependent manner (pEC₅₀ 5.43 ± 0.43) and may serve as a candidate lead compound for the development of new acaricides.

ACVIM consensus update on Lyme borreliosis in dogs and cats

An update of the 2006 American College of Veterinary Internal Medicine (ACVIM) Small Animal Consensus Statement on Lyme Disease in Dogs: Diagnosis, Treatment, and Prevention was presented at the 2016 ACVIM Forum in Denver, CO, followed by panel and audience discussion and a drafted consensus statement distributed online to diplomates for comment. The updated consensus statement is presented below. The consensus statement aims to provide guidance on the diagnosis, treatment, and prevention of Lyme borreliosis in dogs and cats.

Successful treatment of refractory demodicosis and transient papules with a single dose of fluralaner in a dog with uncontrolled severe endocrine disease

A 12-year-old female Shih-Tzu with hyperadrenocorticism and hypothyroidism developed concurrent refractory generalized demodicosis that did not respond to doramectin treatment. Although amitraz treatment was effective, the dog developed severe diabetes, which resulted in the cessation of amitraz and trilostane. Attempts to control the diabetes were unsuccessful, and its hyperadrenocorticism was left untreated, leading to the recurrence of demodicosis. However, demodicosis went into complete remission with a single dose of fluralaner. Transient erythematous papules appeared on the trunk three days after the administration of fluralaner, but no other adverse reactions were noted. We demonstrated that fluralaner is a potent treatment for demodicosis, and skin eruptions are possible after the first dose of the drug.

The acaricidal speed of kill of orally administered fluralaner against poultry red mites (Dermanyssus gallinae) on laying hens and its impact on mite reproduction

BACKGROUND

Dermanyssus gallinae, the poultry red mite, is a growing threat to chickens in poultry farms. This nocturnal hematophagous ectoparasite has a rapid rate of proliferation with a negative impact on the birds' health, welfare and productivity resulting in severe economic consequences for poultry farmers. A study was performed with fluralaner, a novel systemic ectoparasiticide, to evaluate its effect on mite vitality and reproduction after oral administration to laying hens.

METHODS

Sixteen healthy hens were randomly allocated to two study groups (n = 8). One group was orally treated with fluralaner by gavage at a dose of 0.5 mg/kg bodyweight twice 7 days apart. The negative control group received no treatment. Hens in each group were repeatedly infested with approximately 200 unfed adult D. gallinae at 1, 5, 8, 12, 15, 19, 22 and 26 days after the initial administration. After infestation and feeding for 2.5 h, 25 engorged mites per hen were collected and incubated in tubes. Mites were assessed for vitality (dead/live) at 4, 8, 12, and 24 h after each infestation. Tubes containing eggs and/or living mites were incubated another 8 days for assessment of mite reproductive capacity.

RESULTS

Fluralaner demonstrated a fast speed of kill in mites within 4 h post-infestation for 12 days after treatment initiation. An efficacy (mite mortality) of 98.7-100% was achieved. At 15 days after treatment initiation, 100% efficacy was achieved within 24 h post-infestation, and no mite oviposition occurred during this period. Nineteen days after treatment initiation, the mites' ability to generate nymphs was reduced by 90.8%, which decreased to < 24.1% at later infestations.

CONCLUSIONS

Fluralaner administered orally to hens twice, 7 days apart, provides efficacy against experimental poultry red mite infestation for at least 2 weeks. The demonstrated rapid speed of kill results in substantial depletion of the mites' oviposition and suggests that fluralaner can be an effective tool in the control of D. gallinae, one of the most urgent problems in poultry farms.

Laboratory evaluation of the speed of kill of lotilaner (Credelio™) against Ixodes ricinus ticks on dogs

BACKGROUND

With the geographical expansion of tick species and increased recognition of pathogens they transmit, there is a requirement for safe and rapidly effective control measures for dogs. Lotilaner, a novel isoxazoline, is rapidly absorbed following administration of a flavored chewable tablet formulation (Credelio™), providing at least 98% efficacy for at least 1 month following assessments at 48 h post-treatment, and following subsequent challenges. A study was conducted to determine the speed with which lotilaner kills ticks.

METHODS

From 38 dogs, the 32 with the highest Ixodes ricinus counts from a Day -4 infestation were randomized among four groups: two groups were untreated controls, two received lotilaner tablets at a minimum dose rate of 20 mg/kg. Infestations with I. ricinus were performed on Days -2, 7, 14, 21, 28 and 35. Counts were completed 4 and 8 h post-treatment (Day 0), and 8 and 12 h following subsequent infestations. All live ticks were incubated for 24 h following removal from study dogs.

RESULTS

At 4 h post-treatment, there was a 69.8% reduction in geometric mean live tick counts in treated dogs compared to controls. After incubation, the reduction increased to 97.2%. At 8 h after treatment, pre- and post-incubation reductions were 99.2 and 100%, respectively. Following post-treatment challenges, post-incubation efficacy through Day 28 at 8 and 12 h was at least 94.3 and 98.0%, respectively, and was 85.7 and 94.2% at 8 and 12 h after the Day 35 challenge. Mean live tick counts in the lotilaner groups were significantly lower than in the control groups at all assessments through Day 35 at 8 (t ₍₇₎ ≥ 9, P < 0.0001, Days 0 to 28; t ₍₇₎ = 3.54, P ≤ 0.0095, Day 35) and 12 h post-treatment and after subsequent infestations (t ₍₇₎ ≥ 10, P < 0.0001, all days). There were no treatment-related adverse events.

CONCLUSION

Lotilaner at a minimum dose rate of 20 mg/kg began to kill ticks on dogs within 4 h of treatment and efficacy was 100% within 8 h. Lotilaner sustained a rapid kill of newly infesting I. ricinus through 35 days. By quickly killing ticks that infest dogs, lotilaner has potential to help limit the transmission of tick-borne pathogens.

Efficacy of sarolaner (Simparic™) against induced infestations of Amblyomma cajennense on dogs

Background

Amblyomma cajennense is the main vector of Rickettsia rickettsii which causes Brazilian spotted fever. This adult tick preferably infests horses and capybaras, but has low host specificity during its immature stages, thus posing a threat to humans and dogs. In this study, the efficacy of sarolaner (Simparic™/Simparica®, Zoetis) when administered once orally to dogs at 2 mg/kg was evaluated against induced infestations of A. cajennense nymphs for up to 35 days after treatment.

Methods

Based on pretreatment tick counts, 20 dogs were randomly allocated to treatment with sarolaner (Simparic™) dosed at 2 mg/kg of body weight or a placebo on Day 0 of the study. Artificial infestations were performed using laboratory raised A. cajennense nymphs on study days -2, 5, 12, 19, 26 and 33. Efficacy was determined at 48 h post-treatment or post-infestation at each time point relative to the counts for dogs that received placebo.

Results

There were no adverse reactions to treatment. A single dose of sarolaner (Simparic™) provided 100% efficacy on study days 2, 7 and 14; and ≥ 99.6% on days 21, 28 and 35. Geometric mean live tick counts for sarolaner were significantly lower than those for placebo on all days (P < 0.0001).

Conclusions

Under the conditions of the present study, sarolaner (Simparic™) administered once orally at 2 mg/kg provided 100% efficacy against existing infestations and ≥ 99.6% efficacy within 48 h against weekly challenges of A. cajennense for at least 35 days after treatment.

Comparative in vitro evaluation of contact activity of fluralaner, spinosad, phoxim, propoxur, permethrin and deltamethrin against the northern fowl mite, Ornithonyssus sylviarum

Background

Northern fowl mites (Ornithonyssus sylviarum) are obligate hematophagous ectoparasites of both feral birds and poultry, particularly chicken layers and breeders. They complete their entire life-cycle on infested birds while feeding on blood. Infestations of O. sylviarum are difficult to control and resistance to some chemical classes of acaricides is a growing concern. The contact susceptibility of O. sylviarum to a new active ingredient, fluralaner, was evaluated, as well as other compounds representative of the main chemical classes commonly used to control poultry mite infestations in Europe and the USA.

Methods

Six acaricides (fluralaner, spinosad, phoxim, propoxur, permethrin, deltamethrin) were dissolved and serially diluted in butanol:olive oil (1:1) to obtain test solutions used for impregnation of filter paper packets. A carrier-only control was included. Thirty adult northern fowl mites, freshly collected from untreated host chickens, were inserted into each packet for continuous compound exposure. Mite mortality was assessed after incubation of the test packets for 48 h at 75% relative humidity and a temperature of 22 °C.

Results

Adult mite LC₅₀ /LC₉₉ values were 2.95/8.09 ppm for fluralaner, 1587/3123 ppm for spinosad, 420/750 ppm for phoxim and 86/181 ppm for propoxur. Permethrin and deltamethrin LC values could not be calculated due to lack of mortality observed even at 1000 ppm.

Conclusions

Northern fowl mites were highly sensitive to fluralaner after contact exposure. They were moderately sensitive to phoxim and propoxur, and less sensitive to spinosad. Furthermore, the tested mite population appeared to be resistant to the pyrethroids, permethrin and deltamethrin, despite not being exposed to acaricides for at least 10 years.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2289-z) contains supplementary material, which is available to authorized users.

A Bayesian spatio-temporal model for forecasting Anaplasma species seroprevalence in domestic dogs within the contiguous United States

This paper forecasts the 2016 canine Anaplasma spp. seroprevalence in the United States from eight climate, geographic and societal factors. The forecast's construction and an assessment of its performance are described. The forecast is based on a spatial-temporal conditional autoregressive model fitted to over 11 million Anaplasma spp. seroprevalence test results for dogs conducted in the 48 contiguous United States during 2011-2015. The forecast uses county-level data on eight predictive factors, including annual temperature, precipitation, relative humidity, county elevation, forestation coverage, surface water coverage, population density and median household income. Non-static factors are extrapolated into the forthcoming year with various statistical methods. The fitted model and factor extrapolations are used to estimate next year's regional prevalence. The correlation between the observed and model-estimated county-by-county Anaplasma spp. seroprevalence for the five-year period 2011-2015 is 0.902, demonstrating reasonable model accuracy. The weighted correlation (accounting for different sample sizes) between 2015 observed and forecasted county-by-county Anaplasma spp. seroprevalence is 0.987, exhibiting that the proposed approach can be used to accurately forecast Anaplasma spp. seroprevalence. The forecast presented herein can a priori alert veterinarians to areas expected to see Anaplasma spp. seroprevalence beyond the accepted endemic range. The proposed methods may prove useful for forecasting other diseases.

A Bayesian spatio-temporal model for forecasting the prevalence of antibodies to Borrelia burgdorferi, causative agent of Lyme disease, in domestic dogs within the contiguous United States

This paper models the prevalence of antibodies to Borrelia burgdorferi in domestic dogs in the United States using climate, geographic, and societal factors. We then use this model to forecast the prevalence of antibodies to B. burgdorferi in dogs for 2016. The data available for this study consists of 11,937,925 B. burgdorferi serologic test results collected at the county level within the 48 contiguous United States from 2011-2015. Using the serologic data, a baseline B. burgdorferi antibody prevalence map was constructed through the use of spatial smoothing techniques after temporal aggregation; i.e., head-banging and Kriging. In addition, several covariates purported to be associated with B. burgdorferi prevalence were collected on the same spatio-temporal granularity, and include forestation, elevation, water coverage, temperature, relative humidity, precipitation, population density, and median household income. A Bayesian spatio-temporal conditional autoregressive (CAR) model was used to analyze these data, for the purposes of identifying significant risk factors and for constructing disease forecasts. The fidelity of the forecasting technique was assessed using historical data, and a Lyme disease forecast for dogs in 2016 was constructed. The correlation between the county level model and baseline B. burgdorferi antibody prevalence estimates from 2011 to 2015 is 0.894, illustrating that the Bayesian spatio-temporal CAR model provides a good fit to these data. The fidelity of the forecasting technique was assessed in the usual fashion; i.e., the 2011-2014 data was used to forecast the 2015 county level prevalence, with comparisons between observed and predicted being made. The weighted (to acknowledge sample size) correlation between 2015 county level observed prevalence and 2015 forecasted prevalence is 0.978. A forecast for the prevalence of B. burgdorferi antibodies in domestic dogs in 2016 is also provided. The forecast presented from this model can be used to alert veterinarians in areas likely to see above average B. burgdorferi antibody prevalence in dogs in the upcoming year. In addition, because dogs and humans can be exposed to ticks in similar habitats, these data may ultimately prove useful in predicting areas where human Lyme disease risk may emerge.

Blocking transmission of vector-borne diseases

Vector-borne diseases are responsible for significant health problems in humans, as well as in companion and farm animals. Killing the vectors with ectoparasitic drugs before they have the opportunity to pass on their pathogens could be the ideal way to prevent vector borne diseases. Blocking of transmission might work when transmission is delayed during blood meal, as often happens in ticks. The recently described systemic isoxazolines have been shown to successfully prevent disease transmission under conditions of delayed pathogen transfer. However, if the pathogen is transmitted immediately at bite as it is the case with most insects, blocking transmission becomes only possible if ectoparasiticides prevent the vector from landing on or, at least, from biting the host. Chemical entities exhibiting repellent activity in addition to fast killing, like pyrethroids, could prevent pathogen transmission even in cases of immediate transfer. Successful blocking depends on effective action in the context of the extremely diverse life-cycles of vectors and vector-borne pathogens of medical and veterinary importance which are summarized in this review. This complexity leads to important parameters to consider for ectoparasiticide research and when considering the ideal drug profile for preventing disease transmission.

A randomized, blinded, controlled USA field study to assess the use of fluralaner topical solution in controlling canine flea infestations

Background

Orally administered fluralaner effectively controls fleas and ticks on dogs for 12 weeks. This study evaluates the flea control efficacy achieved with topically applied fluralaner in dogs.

Methods

This investigator-blinded, multi-center randomized, positive controlled study evaluated flea control efficacy in dogs following a single owner-applied treatment of topical fluralaner. A positive control group received three treatments, at 4-week intervals, of a commercial formulation of fipronil/(S)-methoprene. All dogs in households randomized to the fluralaner group were dispensed an initial treatment at enrollment and a second treatment at week 12 for an additional 3-week observation of treatment safety. Households with up to five healthy dogs, all at least 12 weeks of age and weighing at least 2 kg (4.4 lb), were randomized in a ratio of 3:1 of fluralaner to positive control. Within households, one primary dog with at least 10 live fleas at enrollment was randomly selected. Flea counts were performed on all primary dogs every 4 weeks through week 12. Efficacy measurement was based on reduction from baseline flea counts. Treatment was considered effective if geometric mean live flea count reductions at weeks 4, 8, and 12 were 90% or greater and significantly different from counts at enrollment. In addition, for each time point the arithmetic mean live flea counts, the efficacy based on arithmetic means, the number and percentage of dogs with at least a 90% reduction in flea count, and the number and percentage of flea free dogs were calculated. Statistical comparisons were also made between treatment groups.

Results

At 12 sites, across 10 states, 121 households (221 dogs) were randomized to receive fluralaner and 44 households (100 dogs) were randomized to receive the positive control. Fluralaner was demonstrated to be significantly effective (all P ≤ 0.0001) at 4 weeks (99.8% reduction), 8 weeks (99.9%), and 12 weeks (99.9%). The positive control was significantly different from baseline (all P ≤ 0.0001) and showed a reduction of 81.2% at 4 weeks and was effective at 8 weeks (90.3%) and 12 weeks (93.0%). Arithmetic mean flea count reductions for the fluralaner group at 4, 8, and 12 weeks were 99.8, 99.9, and 99.9%, respectively. For the positive control, arithmetic mean flea count reductions were 58.8, 75.3, and 80.8% at 4, 8, and 12 weeks, respectively. No treatment-related serious adverse events were reported in either group.

Conclusions

Owner-applied topical fluralaner treatment was safe in dogs and provided ≥ 99.8% flea control efficacy for 12 weeks.

A randomized, blinded, controlled USA field study to assess the use of fluralaner topical solution in controlling feline flea infestations

Background

Fleas are a common ectoparasite of domestic cats and there is a need for novel treatments that improve feline flea control.

Methods

This investigator-blinded, multi-center randomized, positive-controlled study evaluated the flea control in cats provided by a single owner-applied treatment with a fluralaner topical formulation compared with a positive control. Households with up to five healthy cats, all at least 12 weeks of age and weighing at least 1.2 kg (2.6 lb), were randomized in an approximate 3:1 ratio of fluralaner to positive control. All cats in households randomized to the positive control group were dispensed three treatments, at 4-week intervals, of a commercial formulation of fipronil/(S)-methoprene. All cats in households randomized to the fluralaner group were dispensed an initial treatment at enrollment and a second treatment at week 12 for an additional 3-week observation of treatment safety. One primary cat with at least five live fleas at enrollment was randomly selected within each household. Flea counts were performed on all primary cats at 4-week intervals through week 12. Efficacy measurement was based on reduction in flea counts from baseline. Treatment was considered effective at weeks 4, 8 and 12 if mean live flea count reductions were 90% or greater and statistically significantly different (P ≤ 0.05) from counts at enrollment.

Results

In 18 investigational veterinary clinics across 11 USA states, 116 households (224 cats) were randomized to receive topical fluralaner and 45 households (87 cats) were randomized to the fipronil-methoprene combination. Fluralaner was demonstrated to be effective at 4 weeks (99.1% flea count reduction), 8 weeks (99.5%), and 12 weeks (99.0%), and all reductions were significantly different from the enrollment count (all P < 0.0001). The fipronil-methoprene combination was < 90% effective at each post-treatment assessment, with peak efficacy of 75.4% at 12 weeks (all P < 0.0001). No treatment-related serious adverse events were reported in either group.

Conclusions

Owner-applied fluralaner topical treatment was safe in cats and was highly effective in killing fleas over the subsequent 12 weeks.

A comparative laboratory trial evaluating the immediate efficacy of fluralaner, afoxolaner, sarolaner and imidacloprid + permethrin against adult Rhipicephalus sanguineus (sensu lato) ticks attached to dogs

Background

Acaricides are used to treat and prevent tick infestations, and a common clinical scenario is to administer an acaricide on observing an attached tick. Consequently, immediate acaricidal efficacy (onset of activity and speed of kill) results are clinically valuable. This study evaluated the immediate efficacy of four commercially available acaricides against adult Rhipicephalus sanguineus (sensu lato).

Methods

Forty dogs were blocked on hair length and tick carrying capacity, then randomly assigned to receive one of four treatments (fluralaner, sarolaner, imidacloprid + permethrin, or afoxolaner) or left untreated as controls. All dogs were challenged with 50 adult R. sanguineus (s.l.) ticks 48 h prior to treatment. After treatment, in situ tick thumb counts were conducted at 2, 4, 8, 12 and 24 h; thereafter ticks were removed and counted at 48 h.

Results

Imidacloprid + permethrin had the earliest onset of activity at 2 h (36.9% efficacy) followed at 4 h by fluralaner (60.2% efficacy) and sarolaner (48.2% efficacy), and lastly afoxolaner at 8 h (90.8% efficacy). Three oral treatments had an 8 h speed of kill (>90% efficacy) threshold; with corresponding efficacies as: fluralaner (99.6%), sarolaner (94.7%) and afoxolaner (90.8%). Fluralaner and sarolaner achieved 100% efficacy at 12, 24 and 48 h; afoxolaner achieved 100% efficacy at 48 h. Imidacloprid + permethrin achieved 80.1% efficacy at 48 h, therefore, failing to attain the speed of kill 90% efficacy threshold.

Conclusion

The systemically distributed isoxazolines performed much better than cutaneously distributed imidacloprid + permethrin and are optimal treatment choices against attached ticks based on the combination of earlier onset of activity and speed of kill. Fluralaner had a 4 h onset of activity, an 8 h speed of kill and achieved 100% efficacy at 12 h.

Systemically and cutaneously distributed ectoparasiticides: a review of the efficacy against ticks and fleas on dogs

Acaricidal (tick) and insecticidal (flea) efficacy of systemically and cutaneously distributed ectoparasiticide products for dogs are compared based on permethrin and fluralaner as representative molecules. Results of efficacy studies against fleas and ticks are reviewed that show generally good to excellent results. Both externally and systemically distributed treatments have benefits and weaknesses in potentially preventing pathogen transmission by these arthropod vectors.

Four general properties are considered related to the goal of providing optimal reduction in the risk of vector-borne pathogen transmission. These are:

Owner adherence to the recommended treatment protocol;

Rapid onset of activity following administration;

Uniform efficacy over all areas of the treated dog at risk for parasite attachment;

Maintenance of high efficacy throughout the retreatment interval.

In considering these four factors, a systemically distributed acaricide can offer an option that is at least as effective as a cutaneously administered acaricide with regard to the overall goal of reducing the risk of vector-borne pathogen transmission.

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.

Prevention of transmission of Babesia canis by Dermacentor reticulatus ticks to dogs after topical administration of fluralaner spot-on solution

Background

The preventive effect of fluralaner spot-on solution against transmission of Babesia canis by Dermacentor reticulatus ticks was evaluated.

Findings

Sixteen dogs, tested negative for B. canis by polymerase chain reaction (PCR) and immunofluorescence assay test (IFAT), were allocated to two study groups. On day 0, dogs in one group (n = 8) were treated once topically with fluralaner spot-on solution (Bravecto™ Spot-on Solution) according to label recommendations and dogs in the control group (n = 8) remained untreated. On days 2, 28, 56, 70 and 84, all dogs were infested with 50 (±4) D. reticulatus ticks harbouring B. canis, with tick in situ thumb counts 48 ± 4 h after each infestation. On day 90, ticks were removed from all dogs and counted. Prior to each infestation, the presence of B. canis in the respective tick batch was confirmed by PCR, and 12–16 % of ticks were found to be infected with B. canis. Efficacy against ticks was 99.5 and 99.3 % on days 4 and 58 after treatment, respectively and 100 % on all other days. Replacement dogs were included for any B. canis infected control dog (in total 19). All control dogs (n = 27) became infected with B. canis, as confirmed by PCR, performed every 7 days, and by IFAT, performed every 14 days after treatment. None of the eight treated dogs became infected with B. canis, as they were tested negative by PCR and IFAT throughout the study until day 112. By comparing infected dogs in the treated group with infected dogs in the untreated control group, a 100 % preventive effect against B. canis transmission was demonstrated.

Conclusions

A single topical administration of fluralaner spot-on solution effectively prevented the transmission of B. canis by infected D. reticulatus ticks over a 12-week period.

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.

A quantitative evaluation of the extent of fluralaner uptake by ticks (Ixodes ricinus, Ixodes scapularis) in fluralaner (Bravecto) treated vs. untreated dogs using the parameters tick weight and coxal index

Background

Fluralaner is a new antiparasitic drug that was recently introduced as Bravecto^TM chewable tablets for the treatment of tick and flea infestations in dogs. Most marketed tick products exert their effect via topical application and contact exposure to the parasite. In contrast, Bravecto^TM delivers its acaricidal activity through systemic exposure. Tick exposure to fluralaner occurs after attachment to orally treated dogs, which induces a tick-killing effect within 12 h. The fast onset of killing lasts over the entire treatment interval (12 weeks) and suggests that only marginal uptake by ticks is required to induce efficacy. Three laboratory studies were conducted to quantify the extent of uptake by comparison of ticks’ weight and coxal index obtained from Bravecto^TM-treated and negative-control dogs.

Methods

Three studies were conducted using experimental tick infestation with either Ixodes ricinus or Ixodes scapularis after oral administration of fluralaner to dogs. All studies included a treated (Bravecto^TM chewable tablets, MSD Animal Health) and a negative control group. Each study had a similar design for assessing vitality and weighing of ticks collected from dogs of both groups. Additionally, in one study the coxal index (I. ricinus) was calculated as a ratio of tick’s ventral coxal gap and dorsal width of scutum. Tick weight data and coxal indices from Bravecto^TM-treated and negative-control groups were compared via statistical analysis.

Results

Ticks collected from Bravecto^TM-treated dogs weighed significantly less (p ≤ 0.0108) than ticks collected from negative-control dogs, and their coxal index was also significantly lower (p < 0.0001). The difference in tick weights was demonstrated irrespective of the tick species investigated (I. ricinus, I. scapularis). At some assessments the mean tick weights of Bravecto^TM-treated dogs were significantly lower than those of unfed pre-infestation (baseline) ticks. The demonstrated tick-killing efficacy was in the range of 94.6 – 100 %.

Conclusions

Tick weights and coxal indices confirm that a minimal uptake results in a sufficient exposure of ticks to fluralaner (Bravecto^TM) and consequently in a potent acaricidal effect.

Prevention of transmission of Babesia canis by Dermacentor reticulatus ticks to dogs treated orally with fluralaner chewable tablets (Bravecto™)

Background

The preventive effect of fluralaner chewable tablets (Bravecto™) against transmission of Babesia canis by Dermacentor reticulatus ticks was evaluated.

Methods

Sixteen dogs, tested negative for B. canis by PCR and IFAT, were allocated to two study groups. On day 0, dogs in one group (n = 8) were treated once orally with a fluralaner chewable tablet according to label recommendations and dogs in the control group (n = 8) remained untreated. On days 2, 28, 56, 70 and 84, dogs were infested with 50 (±4) B. canis infected D. reticulatus ticks with tick in situ thumb counts 48 ± 4 h post-infestation. Prior to each infestation, the D. reticulatus ticks were confirmed to harbour B. canis by PCR analysis. On day 90, ticks were counted and removed from all dogs. Efficacy against ticks was calculated for each assessment time point. After treatment, all dogs were physically examined in conjunction with blood collection for PCR every 7 days, blood samples for IFAT were collected every 14 days and the dog’s rectal body temperature was measured thrice weekly. From dogs displaying symptoms of babesiosis or were PCR positive, a blood smear was taken, and, if positive, dogs were rescue treated and replaced with a replacement dog. The preventive effect was evaluated by comparing infected dogs in the treated group with infected dogs in the untreated control group.

Results

All control dogs became infected with B. canis, as confirmed by PCR and IFAT. None of the 8 treated dogs became infected with B. canis, as IFAT and PCR were negative throughout the study until day 112. Fluralaner chewable tablet was 100 % effective against ticks on days 4, 30, 58, and 90 and an efficacy of 99.6 % and 99.2 % was achieved on day 72 and day 86 after treatment, respectively. Over the 12-week study duration, a 100 % preventive effect against B. canis transmission was demonstrated.

Conclusions

A single oral administration of fluralaner chewable tablets effectively prevented the transmission of B. canis by infected D. reticulatus ticks over a 12-week period.

A randomized controlled trial of the efficacy of orally administered fluralaner (Bravecto™) against induced Ixodes holocyclus (Australian paralysis tick) infestations on dogs

BACKGROUND

Ixodes holocyclus ticks are a frequently fatal threat to dogs in eastern Australia. These ticks secrete a neurotoxin that can produce an ascending paralysis after 72 h attachment that can lead to death in affected animals. Fluralaner is a potent systemic acaricide with immediate and persistent efficacy for tick control including evidence of 100% efficacy against Ixodes ricinus ticks within 72 h. This study investigated the potential for oral fluralaner administration to control I. holocyclus infestation and the subsequent risk of host paralysis.

METHODS

Healthy Foxhound and Foxhound cross dogs immunized against holocyclotoxin were randomly allocated to receive either a single fluralaner (at least 25 mg/kg) dose or no treatment. All dogs were penned individually and infested with 30 adult unfed female I. holocyclus 1 day before treatment and 14, 28, 42, 56, 70, 84, 112 and 140 days following treatment. Ticks were counted and assessed at 24, 48 and 72 h after the initial fluralaner treatment and after each subsequent infestation. Ticks were not removed at the 24 and 48 h assessments, but were removed after the 72 h assessments. On 112 and 140 days post treatment a new group of untreated control dogs was used.

RESULTS

Fluralaner treatment efficacy against I. holocyclus was 100% at 72 h post treatment. Following re-infestations the efficacy remained at 100% at the 72 h assessments for 115 days and reached 95.7% at 143 days. The differences between mean live tick counts on treatment and control groups were significant (P < 0.00l) at all assessment time points for 143 days following treatment.

CONCLUSIONS

Oral fluralaner treatment can prevent Australian paralysis tick infestations for at least 115 days.

Efficacy of orally administered fluralaner (Bravecto™) or topically applied imidacloprid/moxidectin (Advocate®) against generalized demodicosis in dogs

BACKGROUND

This laboratory study compared the efficacy of Bravecto™ (fluralaner), formulated as a chewable tablet, with the efficacy of Advocate® (imidacloprid/moxidectin), formulated for topical administration, against naturally acquired generalized demodicosis in dogs.

METHODS

Sixteen dogs, all diagnosed with generalized demodectic mange, were randomly allocated to two equal groups. Bravecto™ chewable tablets were administered once orally at a minimum dose of 25 mg fluralaner/kg body weight to one group of dogs, while the second group was treated topically on three occasions at 28-day intervals with Advocate® at a minimum dose of 10 mg imidacloprid/kg body weight and 2.5 mg moxidectin/kg body weight. Mites were counted in skin scrapings and demodectic lesions were evaluated on each dog before treatment and at 28-day intervals thereafter over a 12 week study period. Deep skin scrapings (~4 cm(2)) were made from the same five sites on each dog at each subsequent examination.

RESULTS

After single oral administration of Bravecto™ chewable tablets, mite numbers in skin scrapings were reduced by 99.8% on Day 28 and by 100% on Days 56 and 84. Mite numbers in the dogs treated topically on three occasions at 28-day intervals with Advocate® were reduced by 98.0% on Day 28, by 96.5% on Day 56 and by 94.7% on Day 84. Statistically significantly (P ≤ 0.05) fewer mites were found on Days 56 and 84 on the Bravecto™ treated dogs compared to Advocate® treated dogs. A marked decrease was observed in the occurrence of erythematous patches, crusts, casts and scales in the dogs treated with Bravecto™ and in the occurrence of erythematous patches in the dogs treated with Advocate®. With the exception of one dog in each treated group, all dogs exhibited hair regrowth ≥ 90% at the end of the study in comparison with their hair-coat at study start.

CONCLUSIONS

Single oral administration of Bravecto™ chewable tablets is highly effective against generalized demodicosis, with no mites detectable at 56 and 84 days following treatment. In comparison, Advocate®, administered three times at 28-day intervals, is also highly effective against generalized demodicosis, but most dogs still harboured mites at all assessment time points. Both treatments resulted in a marked reduction of skin lesions and increase of hair re-growth 12 weeks after the initial treatment.

Fluralaner activity against life stages of ticks using Rhipicephalus sanguineus and Ornithodoros moubata IN in vitro contact and feeding assays

Background

Fluralaner is a novel isoxazoline eliciting both acaricidal and insecticidal activity through potent blockage of GABA- and glutamate-gated chloride channels. The aim of the study was to investigate the susceptibility of juvenile stages of common tick species exposed to fluralaner through either contact (Rhipicephalus sanguineus) or contact and feeding routes (Ornithodoros moubata).

Methods

Fluralaner acaricidal activity through both contact and feeding exposure was measured in vitro using two separate testing protocols. Acaricidal contact activity against Rhipicephalus sanguineus life stages was assessed using three minute immersion in fluralaner concentrations between 50 and 0.05 μg/mL (larvae) or between 1000 and 0.2 μg/mL (nymphs and adults). Contact and feeding activity against Ornithodoros moubata nymphs was assessed using fluralaner concentrations between 1000 to 10⁻⁴ μg/mL (contact test) and 0.1 to 10⁻¹⁰ μg/mL (feeding test). Activity was assessed 48 hours after exposure and all tests included vehicle and untreated negative control groups.

Results

Fluralaner lethal concentrations (LC₅₀, LC_90/95) were defined as concentrations with either 50%, 90% or 95% killing effect in the tested sample population. After contact exposure of R. sanguineus life stages lethal concentrations were (μg/mL): larvae - LC₅₀ 0.7, LC₉₀ 2.4; nymphs - LC₅₀ 1.4, LC₉₀ 2.6; and adults - LC₅₀ 278, LC₉₀ 1973. After exposure of O. moubata nymphs to fluralaner lethal concentrations were (μg/mL): contact exposure - LC₅₀ 720_, LC₉₅ 1133; and feeding exposure- LC₅₀ 0.00007, LC₉₅ 0.09.

Conclusions

Fluralaner demonstrates potent in vitro acaricidal activity against all life stages of the brown dog tick, R.sanguineus. The testing of fluralaner contact and feeding routes using O. moubata nymphs demonstrates a high acaricidal activity in both exposure routes.