Efficacy of afoxolaner in a clinical field study in dogs naturally infested with Sarcoptes scabiei

Efficacy of an oral formulation of afoxolaner and milbemycin oxime against Tunga penetrans in naturally infected dogs

BACKGROUND

The sand flea Tunga penetrans is one of the agents of tungiasis, an important parasitic skin disease affecting humans and several mammalian species. Tungiasis is mainly observed in disadvantaged rural and peripheral urban communities in Latin America and sub-Saharan Africa. The dog is a major reservoir of Tunga fleas. Hematophagous adult female Tunga spp. embed and grow in their host's epidermis and cause cutaneous inflammatory disorders. NexGard Spectra® is an orally administered endectocide for dogs, a co-formulation of the isoxazoline afoxolaner and the macrocyclic lactone milbemycin oxime. The objective of this study was to assess the efficacy of this product against canine tungiasis.

METHODS

A blinded, negative-controlled field trial was conducted in a Brazilian community known to be highly endemic for tungiasis. Sixty-six dogs naturally infected with live T. penetrans were randomly allocated to a treated group (44 dogs) and an untreated control group (22 dogs). In a first phase, dogs from the treated group were treated on days 0, 30, and 60. Efficacy was evaluated on the basis of the macroscopic parasitic skin lesions (Fortaleza classification) on days 7, 14, 21, 30, 45, 60, 75, and 90. In a second phase, to evaluate natural reinfections, all dogs were treated on day 90 and evaluated every 2 weeks thereafter until at least 30% of dogs were infected with live sand fleas.

RESULTS

During the first phase, efficacy (reduction in live sand fleas) of 92.4% was demonstrated on day 7. From day 14 until day 90, the efficacy of NexGard Spectra® was 100%. In the second phase, all dogs were free of live T. penetrans from 15 until 45 days after the day 90 treatment; 60 days post-treatment, 11% of dogs were reinfected, and 75 days post-treatment, 40% of dogs were reinfected.

CONCLUSIONS

NexGard Spectra® was demonstrated to be highly effective against canine tungiasis. In addition to an obvious beneficial effect on the health and welfare of the treated dog, the use of this product may have a one-health benefit on human cases by controlling the main reservoir of sand fleas.

The most effective systemic treatment in dogs with sarcoptic mange: a critically appraised topic

BACKGROUND

Sarcoptic mange is a common, pruritic parasitic skin disease of dogs. Due to its highly contagious character, it represents a potential veterinary and public health risk. Because of clinical similarity with other diseases, cross-antigenicity, and low sensitivity of available diagnostic methods, therapeutical trial is frequently used to confirm the disease. Considering the variety of available acaricidal molecules as well as the need to use the most effective treatment, the present paper reviews evidence comparing different types of systemic treatment of canine scabies.

RESULTS

Analysis of the results showed that afoxolaner, fluralaner and sarolaner as well as several macrocyclic lactones such as selamectin, moxidectin and milbemycin oxime can lead to parasitological and clinical cure.

CONCLUSION

The similarity in the clinical and parasitological efficacy of these substances enhances the need for comparative studies, which could allow the identification of the most efficacious product.

Activity, selection response and molecular mode of action of the isoxazoline afoxolaner in Tetranychus urticae

BACKGROUND

Afoxolaner is a novel representative of the isoxazolines, a class of ectoparasiticides which has been commercialized for the control of tick and flea infestations in dogs. In this study, the biological efficacy of afoxolaner against the two-spotted spider mite Tetranychus urticae was evaluated. Furthermore, as isoxazolines are known inhibitors of γ-aminobutyric acid-gated chloride channels (GABACls), the molecular mode of action of afoxolaner on T. urticae GABACls (TuRdls) was studied using functional expression in Xenopus oocytes followed by two-electrode voltage-clamp (TEVC) electrophysiology, and results were compared with inhibition by fluralaner, fipronil and endosulfan. To examine the influence of known GABACl resistance mutations, H301A, I305T and A350T substitutions in TuRdl1 and a S301A substitution in TuRdl2 were introduced.

RESULTS

Bioasassays revealed excellent efficacy of afoxolaner against all developmental stages and no cross-resistance was found in a panel of strains resistant to most currently used acaricides. Laboratory selection over a period of 3 years did not result in resistance. TEVC revealed clear antagonistic activity of afoxolaner and fluralaner for all homomeric TuRdl1/2/3 channels. The introduction of single, double or triple mutations to TuRdl1 and TuRdl2 did not lower channel sensitivity. By contrast, both endosulfan and fipronil had minimal antagonistic activities against TuRdl1/2/3, and channels carrying single mutations, whereas the sensitivity of double and triple TuRdl1 mutants was significantly increased.

CONCLUSIONS

Our results demonstrate that afoxolaner is a potent antagonist of GABACls of T. urticae and has a powerful mode of action to control spider mites. © 2022 Society of Chemical Industry.

Efficacy of afoxolaner (NexGard®) against natural infestations with Trichodectes canis in dogs under field conditions

Background

Trichodectes canis is a small chewing louse found globally that primarily infests dogs. Limited information is available on the efficacy of isoxazolines against infestation with the chewing louse. In the present study, we evaluated the efficacy of afoxolaner, an isoxazoline class compound, in naturally infested domestic dogs.

Methods

The field study was carried out in Romania. Between September 2021 and December 2021, 43 dogs with confirmed T. canis infestation were included in the study. On the day of the inclusion (day 0), each animal was clinically examined and randomly treated with a control product labeled for use against lice [fipronil-(S)-methoprene combination (Frontline Combo®; Boehringer Ingelheim)] or with the investigational product [chewable tablets containing afoxolaner (NexGard®; isoxazoline)]. Each animal was evaluated for the presence of lice at 15 and 30 days post-inclusion.

Results

Of the 48 dogs initially included in the study, 43 completed the treatment period [18 in the control group (CG) and 25 in the investigational group (IG)]. At day 14, no living T. canis lice were detected on the dogs in either group. At day 14, dead lice were detected in four dogs in the IG, while eggs were present in two dogs in the IG and in one dog in the CG. At day 30, no lice were detected in either group, while eggs were still present in one dog in the CG.

Conclusion

These results suggest that afoxolaner is a feasible treatment option against chewing lice in dogs, providing 100% curative efficacy.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05428-y.

Efficacy of afoxolaner for the treatment of ear mite infestation under field conditions

Otodectes cynotis is a commonly occurring surface mite that can be easily transmitted between suitable hosts, including dogs, causing otocariosis. The activity of the systemic insecticide afoxolaner against O. cynotis has been tested once under experimental conditions, showing a high efficacy. The present study aimed to i) assess the efficacy of two consecutive monthly oral administrations of afoxolaner (NexGard®) against O. cynotis in naturally infested dogs under field conditions and ii) evaluate its impact in reducing bacteria or fungal secondary infections. Dogs, positive for O. cynotis (n = 20), were included in the study and allocated in two groups of ten animals each (G1, control group, and G2, treated group). The first group of ear mite-infested dogs was treated with a placebo, while afoxolaner was administered orally to the second group of dogs at Day 0 (D0) and Day 30 (D30), following label instructions. Otoscopic assessments, deep-swab method and swab samples were performed on all dogs (Days 0, 30, 42) to evaluate the presence or absence of live mites and their number throughout the study, as well as to conduct bacterial and fungal assessments. No adverse events likely related were recorded throughout the study. By Day 42 (D42), all dog's ears were flushed to recover ear mites. All treated dogs became negative, as well as two dogs of the control group. The treatment efficacy of afoxolaner was 100 % based on the arithmetic means of the live mite counts. The clinical scores did not change significantly in the control group, whereas they significantly improved in the treated one from D0 to D30 (p-value = 5.47 10^-5). No live mites were present in the afoxolaner-treated group at D42 (p-value = 0.00073). In this field study, two oral administrations of afoxolaner at the recommended dose allowed a complete cure of the infestation. Bacterial and Malassezia pachydermatis infections were detected in both groups, although no significant trend was associated to the ear mite treatment.

A double-blinded placebo-controlled evaluation of adipose-derived mesenchymal stem cells in treatment of canine atopic dermatitis

Mesenchymal stem cells (MSCs) have emerged as a new therapy for various immune-mediated inflammatory diseases. In this study we perform the first double-blinded, placebo-controlled evaluation of the efficacy of adipose-derived allogenic canine MSCs for the treatment of canine atopic dermatitis (cAD). Enrolled canine patients were randomly divided into placebo (PBS saline), low-dose (5 × 10⁵ cells/kg), and high-dose (5 × 10⁶ cells/kg) treatment groups. Each patient received three subcutaneous MSCs treatments or PBS saline at four-week intervals with injections at five sites. Patients were monitored by physical exams, pruritus visual analog scales (PVAS) signed by the primary caretaker, canine atopic dermatitis extent and severity index-4 (CADESI-4) scores by two veterinarians, and complete blood count and serum chemistry analysis along with laboratory analysis for potential biomarkers. Patients were kept off any immune-modulating drugs during the study period, and oral antibiotics and topicals were used for managing pruritus and secondary infections. The PVAS scores and the serum miR-483 levels were significantly lower in the high dose group compared to the placebo group at day90 post first-treatment. The CADESI-4 scores of the high dose group also showed downward trends. No severe adverse effects were observed in any patient in this study. The high dose MSC treatment is efficacious in alleviating the clinical signs of cAD until 30 days after the last subcutaneous administration of MSCs, and miRNA-483 may be a reliable prognostic biomarker for cAD. The MSCs efficacy and potential biomarkers should be further explored by a larger scale clinical trial.

Efficacy of afoxolaner (NexGard®) on the treatment of myiasis caused by the New World screwworm fly Cochliomyia hominivorax (Diptera: Calliphoridae) in naturally infested dogs

New World screwworm (NWS) myiasis is an infestation by Cochliomyia hominivorax larvae that consume the living tissue of warm-blooded animals, including humans. Domestic dogs are among the potential hosts of these flies that lay their eggs on the edges of wounds. NWS myiasis cases can be fatal if untreated. Treatment with parasiticides must be fast-acting, long-lasting and show 100% efficacy, since open wounds can be reinfested. Afoxolaner is a molecule from the isoxazoline family with proven ectoparasiticide action against fleas, ticks and mites in dogs. Fourteen healthy client-owned dogs, naturally infested by C. hominivorax larvae, were treated with afoxolaner (NexGard®) as per label recommendations, providing at least the minimum dosage of 2.5 mg/kg. Maggot infestations were classified as light (fewer than 10 larvae), mild (from 10 to 20 larvae) or severe (more than 20 larvae), according to the number of larvae found in the wound and/or collected from the ground after treatment. Twenty-four hours post-treatment, infested lesions were carefully inspected and collected larvae were counted and classified as live or dead. All maggots were identified as second and third instar larvae of C. hominivorax and were found dead within 24 h after treatment, demonstrating 100% larvicidal efficacy against C. hominivorax.

Efficacy of a novel topical combination of esafoxolaner, eprinomectin and praziquantel against ear mite (Otodectes cynotis) infestations in cats

Esafoxolaner, a purified enantiomer of afoxolaner with insecticidal and acaricidal properties, is combined with eprinomectin and praziquantel, nematodicidal and cestodicidal compounds, in NexGard® Combo, a novel topical endectoparasiticide formulation for cats. The efficacy of this formulation was assessed against Otodectes cynotis in two laboratory studies conducted in South Africa and in the USA with local isolates, and in one field trial conducted in Europe. In each study, cats were randomly allocated to a placebo-treated control group and a novel formulation-treated group. In the laboratory studies, cats were treated at the minimum recommended dose; in the field trial, cats were treated at label dose. All included cats were diagnosed positive for O. cynotis prior to treatment by otoscopy. The main variable of efficacy was a comparison of the number of live O. cynotis collected in both ear canals of all cats in the treated and control groups, one month after treatment. Efficacy of the novel topical formulation exceeded 97% in the three studies. These studies demonstrated the high effectiveness of NexGard® Combo in cats for the treatment of O. cynotis infestations. No health abnormalities were attributed to the treatment in any of the studies.

Current review of isoxazoline ectoparasiticides used in veterinary medicine

The isoxazolines are a novel class of ectoparasiticides with potent inhibitory activity on glutamate- and gamma-aminobutyric acid-gated chloride channel located in nervous system of invertebrates. In recent years, studies have been performed to evaluate the efficacy and safety of isoxazolines against various types of ectoparasites, including fleas, ticks, and mites. As more single and combined isoxazoline products have been approved by the United States Food and Drug Administration and European Medicines Agency, a more comprehensive understanding of isoxazolines becomes essential for veterinary clinical practitioners. This article provides a complete review of isoxazolines with respect to pharmacodynamics, pharmacokinetics, ectoparasiticidal efficacy, and safety, which will provide veterinarians information to allow them to make the best choice of ectoparasiticide for their clients' specific needs.

Insecticidal efficacy of afoxolaner against bedbugs, Cimex lectularius, when administered orally to dogs

The objective of this experimental study was to assess the insecticidal efficacy of afoxolaner (NexGard^®) against bedbugs (Cimex lectularius) on dogs. For each challenge, 20 bedbugs were placed in two chambers positioned in contact to the dog’s skin for 15 min, after which live fed parasites were counted and incubated for survival evaluations. On Day 0, 7 dogs assigned to the treated group were administered afoxolaner orally at the registered dose. All 14 dogs were challenged on Days 1, 7, 14, 21 and 28, and the collected live fed C. lectularius incubated for 72 h (Day 1), and 72 h and 96 h (Days 7, 14, 21 and 28) for survival evaluation. The percent feeding in the control group ranged from 95% to 98.6% and the percent of live fed bedbugs at 96 h ranged from 99.3% to 100% in the control group, demonstrating the viability of the strain and their capacity to feed on dogs. Significantly fewer live fed bedbugs were counted in the treated group, compared to the control group, at all time-points. The reduction of live fed C. lectularius in the afoxolaner group was 41.4% at 72 h after the Day 1 challenge, and 77.2%, 82.7%, 85.0% and 63.5% at 96 h after the Days 7, 14, 21 and 28 challenges, respectively. It is hypothesized that monthly treatment of dogs with afoxolaner could help in preventing a bed bug population from installing in a household if bedbugs bite dogs in the presence of humans.

Clinical, Parasitological, and Serological Follow-Up of Dogs with Sarcoptic Mange Treated Orally with Lotilaner

Canine sarcoptic mange is a highly pruritic and contagious skin disease caused by the mite Sarcoptes scabiei var. canis. This case series describes the clinical, parasitological, and serological follow-up of a cohort of eight adult Saint Bernard dogs with confirmed sarcoptic mange, treated orally with lotilaner. Dogs were evaluated initially and after 14 days and 1, 2, 3, 4, 6, and 12 months for skin lesions, pruritus severity, presence of parasites, and Sarcoptes-IgG levels. A serological indoor allergy panel (IgE) was obtained for seven dogs at day 0 and repeated 12 months later in five dogs to assess potential cross-reactivity between S. scabiei and environmental allergens. Lotilaner was administered to each dog according to the manufacturer's instructions and was repeated after one and two months without any concurrent therapeutic measure or modification of the husbandry conditions. Pruritus ceased after two weeks. The cutaneous score was reduced by 47%, and skin scrapings were negative for all but three animals. All skin scrapings were negative after one month. Lesions were absent after two months. Serological levels decreased gradually, but more slowly than the skin lesions, and two dogs out of six remained positive in the absence of skin lesions or symptoms. All dogs initially tested positive for dust mites and/or storage mites. The IgE titres remained unchanged 12 months later in the five tested dogs. This case report demonstrates the efficacy of lotilaner on scabies in a cohort of infested dogs under natural conditions and the potential antigenic cross-reaction of S. scabiei with house dust and storage mites.

Fluralaner as a novel treatment for sarcoptic mange in the bare-nosed wombat (Vombatus ursinus): safety, pharmacokinetics, efficacy and practicable use

Background

Sarcoptic mange causes significant animal welfare and occasional conservation concerns for bare-nosed wombats (Vombatus ursinus) throughout their range. To date, in situ chemotherapeutic interventions have involved macrocytic lactones, but their short duration of action and need for frequent re-administration has limited treatment success. Fluralaner (Bravecto®; MSD Animal Health), a novel isoxazoline class ectoparasiticide, has several advantageous properties that may overcome such limitations.

Methods

Fluralaner was administered topically at 25 mg/kg (n = 5) and 85 mg/kg (n = 2) to healthy captive bare-nosed wombats. Safety was assessed over 12 weeks by clinical observation and monitoring of haematological and biochemical parameters. Fluralaner plasma pharmacokinetics were quantified using ultra-performance liquid chromatography and tandem mass spectrometry. Efficacy was evaluated through clinical assessment of response to treatment, including mange and body condition scoring, for 15 weeks after topical administration of 25 mg/kg fluralaner to sarcoptic mange-affected wild bare-nosed wombats (n = 3). Duration of action was determined through analysis of pharmacokinetic parameters and visual inspection of study subjects for ticks during the monitoring period. Methods for diluting fluralaner to enable ‘pour-on’ application were compared, and an economic and treatment effort analysis of fluralaner relative to moxidectin was undertaken.

Results

No deleterious health impacts were detected following fluralaner administration. Fluralaner was absorbed and remained quantifiable in plasma throughout the monitoring period. For the 25 mg/kg and 85 mg/kg treatment groups, the respective means for maximum recorded plasma concentrations (C_max) were 6.2 and 16.4 ng/ml; for maximum recorded times to C_max, 3.0 and 37.5 days; and for plasma elimination half-lives, 40.1 and 166.5 days. Clinical resolution of sarcoptic mange was observed in all study animals within 3–4 weeks of treatment, and all wombats remained tick-free for 15 weeks. A suitable product for diluting fluralaner into a ‘pour-on’ was found. Treatment costs were competitive, and predicted treatment effort was substantially lower relative to moxidectin.

Conclusions

Fluralaner appears to be a safe and efficacious treatment for sarcoptic mange in the bare-nosed wombat, with a single dose lasting over 1–3 months. It has economic and treatment-effort-related advantages over moxidectin, the most commonly used alternative. We recommend a dose of 25 mg/kg fluralaner and, based on the conservative assumption that at least 50% of a dose makes dermal contact, Bravecto Spot-On for Large Dogs as the most appropriate formulation for adult bare-nosed wombats.

Graphical abstract

Efficacy of orally and topically administered fluralaner (Bravecto®) for treatment of client-owned dogs with sarcoptic mange under field conditions

Background

Successful canine sarcoptic mange treatment requires immediate efficacy to eliminate active mites, and sustained activity to prevent re-infestation from in-contact animals and fomites. With extended acaricidal activity, fluralaner has been shown to be effective for treating this disease. To confirm this potential under field conditions, two fluralaner formulations were administered to mite-infested, client-owned dogs.

Methods

Households qualified for inclusion if they had at least one dog positive for Sarcoptes scabiei mites, confirmed by skin scraping, and at least one dog with clinical signs evocative of sarcoptic mange. Households were allocated to groups of dogs to receive a single treatment with either oral (Bravecto^® chewable tablets, MSD Animal Health) or topical (Bravecto^® Spot-on, MSD Animal Health), fluralaner at a dose of ≥ 25 mg/kg (range 25–56 mg/kg) on Day 0, or two treatments with oral sarolaner (Simparica^® tablets, Zoetis) (Days 0 and 28) at ≥ 2 mg/kg (2–4 mg/kg). All dogs in each household were treated with the same product. On the enrolment day and subsequently on Days 28, 56 and 84, deep skin scrapings were taken from at least five different body areas judged to be most likely to have active mite infestation. At each visit, the dog’s mange-associated skin lesions were recorded, and pruritus level was assessed.

Results

There were 98 participating households and 135 dogs enrolled across Albania, France, Italy and Portugal. On Day 28, more than 90% of dogs in each group were negative for mites. On Days 56 and 84, all study dogs were free of mites and most dermatological signs of sarcoptic mange had resolved. There were no treatment-related adverse events in any group.

Conclusions

A single treatment of client-owned, sarcoptic mange-affected dogs with either fluralaner chewable tablets or fluralaner spot-on formulation proved a safe and effective treatment of infestations with S. scabiei var. canis, maintained through 84 days (12 weeks) after treatment.

Antiparasitics in Animal Health: Quo Vadis?

Antiparasitics acting on endo- or ectoparasites represent the second largest segment of the global animal health market, accounting for 23% of market share. However, relatively few novel antiparasitic agents have been introduced into the market during recent decades. One exception, and a groundbreaking 21st century success story, are the isoxazolines, whose full potential has not yet been entirely explored. Unfortunately, resistance issues are present across most parasitic diseases, which generates a clear market need for novel resistance-breaking antiparasitics with new modes/mechanisms of action. Recent advances in science and technologies strongly suggest that the time is right to invest in new modalities such as parasitic vaccines or in environmentally friendly interventions.

Afoxolaner as a Treatment for a Novel Sarcoptes scabiei Infestation in a Juvenile Potbelly Pig

A 2 months old female Vietnamese potbellied pig presented to a veterinary teaching hospital with a referring complaint of pruritus. A human caretaker of the pig had recently been diagnosed with a Sarcoptes spp. dermatitis. Microscopic examination of the skin scrape samples and BLAST analysis confirmed the species of the mite as most closely related to Sarcoptes scabiei var. canis (AY493391). The pig was treated with afoxolaner as previous treatment with ivermectin was not efficacious. Recheck examinations and follow up revealed the pig to be non-pruritic and resolving. Afoxolaner may be a therapeutic option when treating Sarcoptes spp. infections in companion pigs.

Efficacy of combination products containing sarolaner, moxidectin and pyrantel (Simparica Trio™) or afoxolaner and milbemycin (NexGard Spectra®) against induced infestations of Ixodes holocyclus in dogs

BACKGROUND

The Australian paralysis tick, Ixodes holocyclus, causes tick paralysis in dogs and cats in the eastern coastal regions of Australia. Prevention is the best option to protect dogs against this potentially fatal disease and sarolaner provides rapid and sustained efficacy against I. holocyclus. In this laboratory study, the efficacy of two combination endectocides containing sarolaner + moxidectin + pyrantel (Simparica Trio™) and afoxolaner + milbemycin (NexGard Spectra^®) was evaluated against an artificial infestation of I. holocyclus.

METHODS

Twenty-four (n =24) foxhounds were randomly allocated to three treatment groups and artificially infested with 30 adult female viable ticks on Days - 1, 7, 14, 21, 28 and 35. On Day 0, dogs in each treatment group were treated with either Drontal^® (control group), Simparica Trio™ at the label dose to provide minimum doses of sarolaner (1.2 mg/kg), moxidectin (24 µg/kg) and pyrantel (5 mg/kg) or NexGard Spectra^® to provide minimum doses of afoxolaner (2.5 mg/kg) and milbemycin (0.5 mg/kg). Live tick counts were performed at 48 and 72 hours after treatment and after each re-infestation on Days 7, 14, 21, 28 and 35. Efficacy was determined at each time point relative to counts for control dogs based on geometric means.

RESULTS

Against an existing infestation, efficacy of both Simparica Trio™ and NexGard Spectra^® was 99.6% and 100% at 48 and 72 h time points, respectively (P = 1.000). Against subsequent weekly infestations, treatment with Simparica Trio™ and NexGard Spectra^® resulted in efficacy of ≥ 97.7% and ≥ 95.5% (P ≥ 0.0911), respectively at the 48 h time point and at the 72 h time point, Simparica Trio™ and NexGard Spectra^® resulted in efficacy of ≥ 99.0% and ≥ 98.4% (P ≥ 0.0511), respectively. There were no treatment-related adverse events in the study.

CONCLUSIONS

Single doses of Simparica Trio™ and NexGard Spectra^® were highly efficacious and provided comparable efficacy against the Australian paralysis tick, I. holocyclus for up to 35 days.

Efficacy of afoxolaner plus milbemycin oxime and afoxolaner alone as treatment for sarcoptic mange in naturally infested dogs

Sarcoptic mange is a pruritic, contagious, ectoparasitic skin disease that affects mammals, including the domestic dog. The objective of this study was to evaluate and compare the efficacy of afoxolaner plus milbemycin oxime (NexGard Spectra) and afoxolaner alone (NexGard) as treatments for sarcoptic mange in naturally infested dogs. A total of 142 dogs naturally infested with Sarcoptes scabiei was evaluated. The dogs were diagnosed by microscopic examinations of skin scrapings. The dogs were divided into 2 groups: 96 dogs were treated with a combined dosage of 2.50 to 5.36 mg/kg body weight (BW) of afoxolaner and 0.50 to 1.07 mg/kg BW of milbemycin oxime and 46 dogs were treated with 2.50 mg/kg BW of afoxolaner alone. The presence or absence of pruritus and lesions were evaluated using an analogous scale on days 7, 14, 21, 28, and 56 after receiving the treatment. Data obtained were analyzed by Student's t-test (P ≤ 0.05). The single oral treatment of afoxolaner plus milbemycin oxime resulted in a significant reduction in pruritus of 87.4% at 28 d after treatment (P ≤ 0.05). Resolution of the lesions after treatment was variable, with a significant decrease (P ≤ 0.05) observed within the first 14 d, although this parameter continued to improve until the end of the study on day 28, when a decrease of 96% was observed. By the end of the study, a single dose of either the afoxolaner alone or the afoxolaner combined with milbemycin oxime was effective in significantly reducing the signs associated with sarcoptic mange during a 56-day evaluation period.

Assessment of the insecticidal activity of oral afoxolaner against Phlebotomus perniciosus in dogs

Twelve healthy dogs were included in this laboratory efficacy study. Six dogs were randomly allocated based on body weight to an untreated control group and six to an afoxolaner (NexGard^®) treated group. In the treatment group, afoxolaner was administered orally on Day 0 in accordance with label instructions. On Days 1, 14 and 28, each dog was exposed to 60 unfed female and 10 male Phlebotomus perniciosus sandflies for 1 h. At the end of each exposure period, sandflies were counted and assessed for viability and feeding status. There was no statistical difference in mortality (0.0–5.4%), nor in feeding proportion (61.6–78%) between the control and the treated groups at all 1-h post-exposure assessments. After collection, live fed and unfed sandflies were kept for viability assessments at 48 and 72 h post-exposure. In the untreated control group, the average percentages of live, fed, female sandflies after exposure, on Days 1, 14 and 28, ranged from 51% to 74% at 48 h and from 46% to 57% at 72 h, demonstrating model robustness over the 28 days of the study. Significantly fewer live fed sandflies were recorded for the afoxolaner treated group (p < 0.01). The insecticidal efficacy was 100%, 95.9% and 75.2% at 48 h post Days 1, 14 and 28 exposures, respectively, and 100%, 100% and 86.3% at 72 h post Days 1, 14, and 28 exposures, respectively. A single administration of oral afoxolaner (NexGard^®) to dogs significantly killed P. perniciosus sandflies 48 and 72 h after blood feeding for 1 month.

The Challenge of Developing a Single-Dose Treatment for Scabies

Scabies is a common skin disease with an estimated worldwide incidence of 200 million people infected per year. Its morbidity and mortality is principally due to secondary bacterial infections, a link now well recognized and prompting the recent inclusion of this disease-complex in the WHO list of neglected tropical diseases. The few treatments available are poorly effective against Sarcoptes scabiei eggs and appear to induce resistance in the parasite. An ideal alternative would be a single-dose regimen that kills all developmental stages, including eggs. Drugs used in the veterinary field and applied to other arthropods could be tested experimentally in an established pig-scabies model. Moreover, functional genomics combined with target validation through biochemical research should assist in identifying new drugs.

A review of sarcoptic mange in North American wildlife

The "itch mite" or "mange mite", Sarcoptes scabiei, causes scabies in humans and sarcoptic mange in domestic and free-ranging animals. This mite has a wide host range due to its ability to adapt to new hosts and has been spread across the globe presumably through human expansion. While disease caused by S. scabiei has been very well-studied in humans and domestic animals, there are still numerous gaps in our understanding of this pathogen in free-ranging wildlife. The literature on sarcoptic mange in North American wildlife is particularly limited, which may be due to the relatively limited number of clinically-affected species and lack of severe population impacts seen in other continents. This review article provides a summary of the current knowledge of mange in wildlife, with a focus on the most common clinically-affected species in North America including red foxes (Vulpes vulpes), gray wolves (Canis lupus), coyotes (Canis latrans), and American black bears (Ursus americanus).

Treatment of canine sarcoptic mange with afoxolaner (NexGard®) and afoxolaner plus milbemycin oxime (NexGard Spectra®) chewable tablets: efficacy under field conditions in Portugal and Germany

The efficacy of NexGard^® and NexGard Spectra^® against sarcoptic mange in dogs was evaluated in a clinical field study. Skin scrapings from dogs presenting signs suggestive of sarcoptic mange were examined to confirm infestation. A total of 106 dogs were screened at eight sites in Portugal and Germany. In all, 80 dogs that had demonstrated ≥5 live Sarcoptes mites in five skin scrapings were enrolled, scored for specific clinical signs (pruritus; papules and crusts; alopecia), and allocated at random to receive either NexGard^® or NexGard Spectra^® twice, one month apart per label instructions. To determine efficacy, live Sarcoptes mites in five skin scrapings per dog were counted, and clinical signs were scored one month and two months after first treatment and compared to pre-treatment (baseline) values. Based on compliance, 65 dogs were determined to be evaluable cases at the end of the study. The efficacy, in terms of reduction of geometric mean live Sarcoptes mite counts, was 98.9% and 99.7% for NexGard^®-treated (n = 38) and 99.6% and 100% for NexGard Spectra^®-treated dogs (n = 27) at one month and two months after treatment initiation (p < 0.001, both treatments). Both treatments resulted in a significant improvement in pruritus, papules and crusts, and alopecia one month and two months after treatment initiation (p = 0.0001, both treatments). In conclusion, this field study confirms that both NexGard^® and NexGard Spectra^® administered twice one month apart provide an effective and safe treatment against sarcoptic mange in dogs.

Estimating the efficacy of community-wide use of systemic insecticides in dogs to control zoonotic visceral leishmaniasis: A modelling study in a Brazilian scenario

Systemic insecticides in dogs have been suggested as a public health intervention to prevent human cases of Zoonotic Visceral Leishmaniasis (ZVL). But, currently there are no systemic insecticides for dogs registered against zoo-anthropophilic pool blood feeding phlebotomine flies. We predict the impact of community-wide use of systemic insecticide in dog populations as a public health measure to control transmission of Leishmania infantum to humans using a mathematical model. We developed a Susceptible-Exposed-Infected (SEI) compartmental model to describe L. infantum transmission dynamics in dogs, with a vectorial capacity term to represent transmission between L. infantum-hosting dogs via phlebotomine flies. For Infected (I) dogs two levels of infectiousness were modelled, high infectiousness and low infectiousness. Human incidence was estimated through its relationship to infection in the dog population. We evaluated outcomes from a wide range of scenarios comprising different combinations of initial insecticide efficacy, duration of insecticide efficacy over time, and proportion of the dog population treated (60%, 70% & 80%). The same reduction in human infection incidence can be achieved via different combinations of insecticide efficacy, duration and dog coverage. For example, a systemic insecticide with an initial efficacy of 80% and 6 months above 65% efficacy would require treating at least 70% of the dogs to reduce the human infection incidence by 50%. Sensitivity analysis showed that the model outcome was most sensitive to baseline values of phlebotomine fly daily survival rate and insecticide coverage. Community-wide use of systemic insecticides applied to the “L. infantum canine reservoir” can significantly reduce human incidence of L. infantum infection. The results of this mathematical model can help defining the insecticide target product profile and how the insecticide should be applied to maximise effectiveness.

Zoonotic visceral leishmaniasis (ZVL) is a potentially deadly disease in humans caused by Leishmania infantum. This leishmania species can be delivered by pool blood feeding zoo-anthropophilic phlebotomine flies to several mammals, the dog population being recognized as the main reservoir. Transmission from infected dogs to humans is through the bite of female phlebotomine sand flies. The disease is endemic in several countries and Brazil has a high prevalence of cases with over 3000 ZVL cases reported per year. The main, inefficient and highly controversial, control measure in Brazil has been culling sero-positive dogs. The community-wide use of systemic insecticides in dogs could be an alternative to control L. infantum transmission from phlebotomine flies to humans. The rationale is that phlebotomine flies which sampled their blood meals from dogs treated with systemic insecticides would die reducing the risk of L. infantum transmission. To reduce the number of ZVL cases, a large proportion of dogs in the community should be treated and the systemic insecticide used should be effective in killing phlebotomine flies acting as vectors of L. infantum parasites for a significant amount of time. We used a mathematical model mimicking L. infantum transmission to show that this novel vector control strategy could be effective. We identified the combination of different key parameters (e.g. insecticide efficacy, duration and proportion of dogs treated) that could lead to a significant reduction of the risk of L. infantum infection in humans.

Efficacy of two formulations of afoxolaner (NexGard® and NexGard Spectra®) for the treatment of generalised demodicosis in dogs, in veterinary dermatology referral centers in Europe

Background

A multi-centre field trial was conducted to evaluate the efficacy of afoxolaner based chewables (NexGard® or NexGard Spectra®) for the treatment of generalised demodicosis caused by Demodex canis in dogs under field conditions in France, Italy and Poland.

Methods

Client-owned dogs, diagnosed positive for Demodex mites by pre-treatment skin scrapings and presenting clinical signs of generalised demodicosis were included. Dogs were orally treated with afoxolaner three times at monthly intervals. Of the 50 dogs enrolled, 48 completed the whole study. Efficacy of the treatments was assessed monthly by Demodex mite counts and physical examination with special regard to the severity and extension of skin lesions.

Results

Treatments were well tolerated in all dogs and resulted in a rapid reduction of mites, with all post-treatment mite counts significantly lower than baseline. The number of mites was reduced by 87.6%, 96.5% and 98.1% on Days 28, 56 and 84, respectively. In addition, the skin lesion severity and extent scores as well as the pruritus were all significantly lower at all post-treatment visits compared to the pre-treatment assessment.

Conclusions

This clinical field study demonstrated that monthly administrations of afoxolaner in NexGard® or NexGard Spectra®, offered a convenient and reliable solution for the treatment of canine generalised demodicosis.

Efficacy and Pharmacokinetics Evaluation of a Single Oral Dose of Afoxolaner against Sarcoptes scabiei in the Porcine Scabies Model for Human Infestation

Scabies is a major and potentially growing public health problem worldwide with an unmet need for acaricidal agents with greater efficacy and improved pharmacological properties for its treatment. The objective of the present study was to assess the efficacy and describe the pharmacokinetics profile of a novel acaricide, afoxolaner (AFX), in a relevant experimental porcine model. Twelve pigs were experimentally infested and either treated with 2.5 mg/kg single dose oral AFX (n = 4) or 0.2 mg/kg, two doses 8 days apart, oral ivermectin ([IVM] n = 4) or not treated for scabies (n = 4). The response to treatment was assessed by the reduction of mite counts in skin scrapings as well as clinical and pruritus scores over time. Plasma and skin pharmacokinetics profiles for both AFX and IVM were evaluated. AFX efficacy was 100% at days 8 and 14 posttreatment and remained unchanged until the study end (day 45). IVM efficacy was 86% and 97% on days 8 and 14, respectively, with a few mites recovered at the study end. Clinical and pruritus scores decreased in both treated groups and remained constant in the control group. Plasma mean residence times (MRT) were 7.1 ± 2.4 and 1.1 ± 0.2 days for AFX and IVM, respectively. Skin MRT values were 16.2 ± 16.9 and 2.7 ± 0.5 days for AFX and IVM, respectively. Overall, a single oral dose of AFX was efficacious for the treatment of scabies in experimentally infested pigs and showed remarkably long MRTs in plasma and, notably, in the skin.

Assessment of the insecticidal activity of afoxolaner against Aedes aegypti in dogs treated with NexGard®

Twelve healthy dogs were studied in this parallel group, blinded, randomised, and negative controlled efficacy study. On Day -1, the 12 dogs included were ranked within sex in descending order of individual pre-treatment (Day -5) fed mosquito counts and randomly allocated by blocks of two dogs to the untreated control group or the afoxolaner-treated group. NexGard^® (Merial, now part of Boehringer Ingelheim Animal Health) was administered orally on Day 0 in accordance with the European label instructions. On Days 1, 7, 14, 21 and 28, all dogs were exposed for a duration of 1 hour to 50 ± 5 unfed Aedes aegypti females. After each exposure, mosquitoes were collected after 1 hour and assessed for viability during collection and at 24 ± 2 hours. The arithmetic (and geometric) mean values of live fed mosquito counts at 24 hours after the exposure periods for the negative control group ranged from 33.7 (32.3) to 49.8 (49.7), indicating that this was a vigorous mosquito strain. There was no significant difference between control and treated groups in the number of live and fed mosquitoes at each 1 hour post-exposure collection time. Based on arithmetic and geometric mean values at 24 hours after each exposure, significantly fewer live fed mosquitoes were recorded in the treated group, compared to the negative control group, throughout the study (p < 0.001). The afoxolaner insecticidal efficacy against A. aegypti varied from 98% (Day 2) to 75.3% (Day 29) based on arithmetic means, and 98.7% (Day 2) to 89.8% (Day 29) based on geometric means.

Assessment of afoxolaner efficacy against Otodectes cynotis infestations of dogs

BACKGROUND

The efficacy of a single 2.5 mg/kg dose of afoxolaner (NexGard®, Merial) against induced Otodectes cynotis infestations was assessed in eight afoxolaner-treated dogs, compared to eight untreated dogs.

METHODS

After O. cynotis infestations were established and confirmed by otoscopic assessments in 16 dogs, all of the dogs were included in the study and allocated to two separate treatment groups. The first group of eight ear mite-infested dogs remained untreated, while afoxolaner was administered orally to the second group of dogs at the minimum recommended dose once on Day 0. Otoscopic assessments performed on all dogs (Days -7, -2, 14 and 28) confirmed the presence or absence of live mites throughout the study. No serious adverse events were recorded throughout the study, and no adverse events were likely related to the administration of NexGard.

RESULTS

By Day 28, seven out of eight untreated dogs were still infested with ear mites, while only two out of eight afoxolaner-treated dogs were infested, with one and four ear mites, respectively. On Day 28, the reductions of mite counts in the afoxolaner-treated group versus those of the control dogs were 98.5% based on geometric means, and 99.4% based on arithmetic means. Significantly fewer (P < 0.05) live mites were present in the afoxolaner-treated group than the untreated group on Day 28.

CONCLUSION

The results of this study demonstrated that a single oral administration of afoxolaner at the minimum recommended dose is highly effective (>98%) in treating dogs with induced O. cynotis infestations.