Isoxazolines: A Novel Chemotype Highly Effective on Ectoparasites

Recent developments in fluorine-containing pesticides

To ensure ongoing sustainability, the modern agrochemical industry is faced with enormous challenges. These arise from provision of high-quality food to increasing water use and environmental impact as well as a growing world population. The loss of previous agrochemicals due to consumer perception, changing grower needs and ever-changing regulatory requirements is higher than the number of active ingredients that are being introduced into the crop protection market. Therefore, the development of novel agrochemicals is essential to provide improved efficacy and environmental profiles. In this context, the introduction of fluorine atoms and fluorine-containing motifs into a molecule is an important method to influence its physicochemical properties. These include, for example, small difluoro- and trifluoromethyl, or trifluoromethoxy groups at aryl or heterocyclic aryl moieties but also fragments like 2,2,2-trifluoroethoxycarbonyl, trifluoromethylsulfonyl, trifluoroacetyl, as well as the so far unusal rest like heptafluoro-iso-propyl. This review gives an overview of recent developments of fluorine-containing pesticides launched over the past 7 years and describes a selection of current fluorine-containing development candidates. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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®.

Effect of fluralaner on the biology, survival, and reproductive fitness of the neotropical malaria vector Anopheles aquasalis

BACKGROUND

Reducing mosquito abundance or interfering with its ability to support the parasite cycle can help to interrupt malaria in areas of significant risk of malaria transmission. Fluralaner is a safe and effective drug for veterinary use indicated for the treatment against fleas and ticks which acts as an antagonist of chloride ion channels mediated by γ-aminobutyric acid (GABA), preventing the entry of these ions into the postsynaptic neuron, leading to hyperexcitability of the postsynaptic neuron of the central nervous system of arthropods. Fluralaner demonstrated insecticidal activity against different insect species.

METHODS

The study aimed to evaluate the effects of fluralaner on the biology, survival, and reproductive fitness of Anopheles aquasalis. The following lethal concentrations (LC) were determined for An. aquasalis: LC5 = 0.511 µM; LC25 = 1.625 µM; LC50 = 3.237 µM.

RESULTS

A significant decrease (P < 0.001) was evident in the number of eggs, larvae, and pupae in the group exposed to a sublethal dose of fluralaner when compared to a control group (without the drug). Using blood from dogs after administration of fluralaner, it was observed that the drug causes 100% mortality in An. aquasalis in less than 24 h after feeding; this effect remains even after 90 days in all samples.

DISCUSSION

Fluralaner showed the same result for up to 60 days, and after that, there was a slight reduction in its effect, evidenced by a decrease in the percentage of dead females; however, still significant when compared to the control group.

CONCLUSION

Fluralaner affects the biology and reduction of survival in An. aquasalis in a lasting and prolonged period, and its fecundity with lower dosages, is a strong candidate for controlling disease vectors.

Complete bacterial profile and potential pathogens of cat fleas Ctenocephalides felis

Fleas are important ectoparasites and vectors associated with a wide range of pathogenic diseases, posing threats to public health concerns, especially cat fleas that spread worldwide. Understanding the microbial components is essential due to cat fleas are capable of transmitting pathogens to humans, causing diseases like plague and murine typhus. In the present study, metagenomic next-generation sequencing was applied to obtain the complete microbiota and related functions in the gut of Ctenocephalides felis. A total of 1,870 species was taxonomically recognized including 1,407 bacteria, 365 eukaryotes, 69 viruses, and 29 archaea. Proteobacteria was the dominant phylum among the six samples. Pathogens Rickettsia felis, Acinetobacter baumannii, Coxiella burnetii, and Anaplasma phagocytophilum were taxonomically identified and had high abundances in all samples. The resistance gene MexD was predominant in microbial communities of all cat fleas. We also performed epidemiological surveys of pathogens R. felis, A. baumannii, C. burnetii, and A. phagocytophilum among 165 cat fleas collected from seven provinces in China, while only the DNAs of R. felis (38/165, 23.03%) and C. burnetii (2/165, 1.21%) were obtained. The data provide new insight and understanding of flea intestinal microbiota and provided novel information for preventing and controlling fleas and their transmitted diseases.

Discovery of a Novel Class of Acylthiourea-Containing Isoxazoline Insecticides against Plutella xylostella

Isoxazoline structures are widely found in natural products and are rich in biological activities. This study discloses the development of a series of novel isoxazoline derivatives by introducing acylthiourea fragments to access insecticidal activity. All synthetic compounds were examined for their insecticidal activity against Plutella xylostella, with results showing moderate to strong activity. Based on this, the structure-activity relationship analysis was carried out via the constructed three-dimensional quantitative structure-activity relationship model to further guide the structure optimization, resulting in the optimal compound 32. The LC₅₀ of compound 32 against Plutella xylostella was 0.26 mg/L, demonstrating better activity than the positive control, ethiprole (LC₅₀ = 3.81 mg/L), avermectin (LC₅₀ = 12.32 mg/L), and compounds 1-31. The insect GABA enzyme-linked immunosorbent assay demonstrated that compound 32 might act on the insect GABA receptor, and the molecular docking assay further illustrated the mode of action of compound 32 with the GABA receptor. In addition, the proteomics analysis indicated that the action of compound 32 on Plutella xylostella was multi-pathway.

Design, Synthesis, and Insecticidal and Fungicidal Activities of Ether/Oxime-ether Containing Isoxazoline Derivatives

The existing agricultural insecticides have developed drug resistance from long-term use. Isoxazoline derivatives are new insecticides discovered in the 21st century. Because of their unique insecticidal mechanism, high selectivity, safety, and no significant cross resistance with the existing pesticides on the market, they have become a hot spot in the field of pesticide research. Herein, a series of novel isoxazoline derivatives containing ether and oxime-ether structures were designed and synthesized by a scaffold-hopping strategy using the pesticide fluralaner as a template structure. Through the investigation of insecticidal activity and the systematic structure-activity relationship, a series of compounds with high insecticidal activities were found, and compounds I-4, II-9, and II-13 with LC₅₀ values of 0.00008-0.00036 mg/L against diamondback moth emerged as novel insecticide candidates. These compounds also exhibited broad spectrum fungicidal activities against 14 plant fungi. The current work provides a reference for the design of new isoxazoline compounds based on the scaffold-hopping strategy.

Pharmacokinetic and pharmacodynamic considerations for treating sarcoptic mange with cross-relevance to Australian wildlife

Sarcoptes scabiei is the microscopic burrowing mite responsible for sarcoptic mange, which is reported in approximately 150 mammalian species. In Australia, sarcoptic mange affects a number of native and introduced wildlife species, is particularly severe in bare-nosed wombats (Vombatus ursinus) and an emerging issue in koala and quenda. There are a variety of acaricides available for the treatment of sarcoptic mange which are generally effective in eliminating mites from humans and animals in captivity. In wild populations, effective treatment is challenging, and concerns exist regarding safety, efficacy and the potential emergence of acaricide resistance. There are risks where acaricides are used intensively or inadequately, which could adversely affect treatment success rates as well as animal welfare. While reviews on epidemiology, treatment strategies, and pathogenesis of sarcoptic mange in wildlife are available, there is currently no review evaluating the use of specific acaricides in the context of their pharmacokinetic and pharmacodynamic properties, and subsequent likelihood of emerging drug resistance, particularly for Australian wildlife. This review critically evaluates acaricides that have been utilised to treat sarcoptic mange in wildlife, including dosage forms and routes, pharmacokinetics, mode of action and efficacy. We also highlight the reports of resistance of S. scabiei to acaricides, including clinical and in vitro observations.

Theoretical and Experimental Study of Molecular Interactions of Fluralaner with Lipid Membranes

Fluralaner is a relatively new insecticide belonging to the isoxazoline group, whose action mechanism involves the blocking of GABA_A-receptors in the insect nervous system. Because of its high hydrophobicity, fluralaner could bioaccumulate and reach toxic local concentrations. Since there are no data available about the penetration and persistence of isoxazolines in biological membranes, we intend to evaluate fluralaner permanence as a pollutant by using model membranes. We used experimental and in silico models to characterize the incorporation of fluralaner into the lipid phase at different packing states. We determined its impact in the membrane structure and organization. Our results confirm that fluralaner is capable of penetrating, holding, and accumulating in the lipid membrane and provide details on its precise location and orientation. These properties would allow fluralaner to reach high local concentrations in different membranes and organs, which could be dangerous for vertebrate organisms if its handling is not properly controlled.

A rapid evidence assessment of the potential risk to the environment presented by active ingredients in the UK's most commonly sold companion animal parasiticides

A number of parasiticides are commercially available as companion animal treatments to protect against parasite infestation and are sold in large volumes. These treatments are not intended to enter the wider environment but may be washed off or excreted by treated animals and have ecotoxic impacts. A systematic literature review was conducted to identify the existing evidence for the toxicity of the six most used parasiticides in the UK: imidacloprid, fipronil, fluralaner, afoxolaner, selamectin, and flumethrin. A total of 17,207 published articles were screened, with 690 included in the final evidence synthesis. All parasiticides displayed higher toxicity towards invertebrates than vertebrates, enabling their use as companion animal treatments. Extensive evidence exists of ecotoxicity for imidacloprid and fipronil, but this focuses on exposure via agricultural use and is not representative of environmental exposure that results from use in companion animal treatments, especially in urban greenspace. Little to no evidence exists for the ecotoxicity of the remaining parasiticides. Despite heavy usage, there is currently insufficient evidence to understand the environmental risk posed by these veterinary treatments and further studies are urgently needed to quantify the levels and characterise the routes of environmental exposure, as well as identifying any resulting environmental harm.

Safety of oral afoxolaner formulated with or without milbemycin oxime in homozygous MDR1-deficient collie dogs

Afoxolaner, an insecticide and acaricide compound of the isoxazoline class, is available for dogs as an oral ectoparasiticide medicine (NexGard®) and as an oral endectoparasiticide medicine in combination with milbemycin oxime (MO), a macrocyclic lactone (NexGard® Spectra). The safety of these two compounds, alone or in combination, was investigated in homozygous MDR1‐deficient collie dogs, in two studies. Overall, 30 adult collie dogs were treated once orally, 9 with a placebo, 9 with afoxolaner, 6 with MO, and 6 with a combination of afoxolaner and MO. For afoxolaner, the mean investigated dosage corresponded to 3.8 and 4.7 multiples of the maximum recommended therapeutic doses (RTD) in NexGard® and NexGard® Spectra, respectively. For MO, the mean investigated dosage corresponded to 4.7 multiples of the maximum RTD in NexGard® Spectra. Dogs were closely monitored for adverse reactions on the day of treatment and for the following two days. No significant adverse reaction was observed in any dog from the afoxolaner or the afoxolaner + MO groups; in the MO‐only treated group, mild and transient neurological signs were observed during the 4–8 h post‐treatment window. These studies demonstrated a high level of safety of oral afoxolaner, alone or in combination with milbemycin oxime, in homozygous MDR1‐deficient dogs.

Design, synthesis, and insecticidal and fungicidal activities of quaternary ammonium salt derivatives of a triazolyphenyl isoxazoline insecticide

BACKGROUND

Insect pests seriously decrease the yield and quality of agricultural crops. Resistance to commonly used insecticides is increasingly undermining their effectiveness, and therefore the development of agents with novel modes of action is desirable. Isoxazolines are a new class of insecticides that act on γ-aminobutyric acid (GABA) gated chloride channels. In this work, we used the highly active 4-triazolyphenyl isoxazoline DP-9 as a parent structure to design and synthesize a series of quaternary ammonium salt (QAS) derivatives, and we systematically evaluated their insecticidal and antifungal activities.

RESULTS

Many of the synthesized QASs exhibit insecticidal activities equivalent to or higher than that of DP-9. In particular, compounds I-31 (93%, 0.00005 mg/L) and I-34 (80%, 0.00001 mg/L) showed insecticidal activities against diamondback moth larvae that were 2-10 times higher than those of fluralaner (70%, 0.0001 mg/L) and DP-9 (80%, 0.0001 mg/L), in addition to showing excellent activities against oriental armyworm, fall armyworm, cotton bollworm, corn borer, and mosquito larvae. Furthermore, all of the synthesized compounds also showed broad-spectrum fungicidal activities.

CONCLUSION

The insecticidal activities of QAS derivatives of DP-9 were the same as or better than the activity of DP-9. Compounds I-31 and I-34 showed better insecticidal activities against diamondback moth larvae than fluralaner and DP-9, and thus are promising new candidates for insecticide research.

State-dependent inhibition of GABA receptor channels by the ectoparasiticide fluralaner

γ-Aminobutyric acid (GABA) receptors (GABARs) are ligand-gated Cl^- channels, which cause an influx of Cl^- that inhibits excitation in postsynaptic cells upon activation. GABARs are important targets for drugs and pest control chemicals. We previously reported that the isoxazoline ectoparasiticide fluralaner inhibits GABA-induced currents in housefly (Musca domestica) GABARs by binding to the putative binding site in the transmembrane subunit interface. In the present study, we investigated whether fluralaner inhibits the GABA response in the GABAR activated state, the resting state, or both, using two-electrode voltage clamp electrophysiology protocols. We found that inhibition progresses over time to steady-state levels by repeated short applications of GABA during fluralaner perfusion. The GABA response was not impaired by fluralaner treatment in the GABAR resting state. However, once inhibited, the GABA response was not restored by repeated applications of GABA. These findings suggest that fluralaner might reach the binding site of the activated conformation of GABARs in a stepwise fashion and tightly bind to it.

Insecticidal efficacy against Phlebotomus perniciosus in dogs treated orally with fluralaner in two different parallel-group, negative-control, random and masked trials

Background

Dogs are the reservoir host of Leishmania infantum, the agent of zoonotic visceral leishmaniasis (VL), which is transmitted by the bite of phlebotomine sand flies. The sand fly Phlebotomus perniciosus is the main vector of zoonotic VL in the western Mediterranean region. Fluralaner has been shown to effectively kill this vector. The aim of this study was to evaluate the insecticidal efficacy of oral fluralaner in dogs bitten by P. perniciosus.

Methods

Two parallel-group, negative-controlled, randomized, masked laboratory trials with equivalent designs were performed in two different locations using two different pathogen-free laboratory-bred P. perniciosus strains for the challenge. In each trial, 12 purpose-bred beagles, initially ranked on natural attractiveness to sand flies, were randomly allocated to two groups (6 animals/group). Dogs in one group received fluralaner orally at the approved dose on day 0, and dogs in the control group were not treated. Each dog was subsequently exposed to an average of 70 unfed live sand fly females on days 1, 28, 56 and 84. Viability of blood-fed females was then evaluated for up to 96 h after exposure, and insecticidal efficacy was measured as the survival rate of flies fed on the fluralaner-treated dogs versus that of dogs in the control group. Significance was calculated for the proportion of live fed sand fly counts from treated versus control group dogs.

Results

Comparison of the survival proportions between treated and control groups showed that fluralaner insecticidal efficacy was highly significant in both trials (P < 0.001 or P < 0.01 in different assessments) through to day 56. In the first trial, efficacy reached 100% on days 1 and 28, and 99.1% on day 56; in the second trial, the insecticidal efficacy was 98.5, 100 and 85.9%, respectively on the same days. On day 84, efficacy was in the range of 53–57% (P < 0.05) in the first trial and 0% in the second trial.

Conclusion

A single oral fluralaner administration to dogs under laboratory conditions results in strong and reproducible insecticidal efficacy against P. perniciosus for at least 8 weeks.

Graphical Abstract

Assay of afoxolaner and determination of its related substances in commercial bulk batches of afoxolaner by reversed-phase HPLC method based on a short octadecyl column

Afoxolaner is a new insecticidal and acaricidal active pharmaceutical ingredient (API) belonging to the isoxazoline family, widely prescribed for the control of fleas and ticks in dogs. A stability-indicating reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed for the assay of afoxolaner and determination of its related compounds in bulk API lots of afoxolaner. The chromatographic separation of afoxolaner and its related compounds was achieved by gradient elution on a Zorbax-SB C18 column (50 mm × 4.6 mm i.d., 5 µm particle size) maintained at 40 °C. Mobile phase-A is composed of water and mobile phase-B is composed of acetonitrile/methanol (50/50, v/v). Analytes were monitored by UV detection at 225 nm with a flow rate of 2.0 mL/min. The stability-indicating capability of the method has been demonstrated by adequate separation of all the process related impurities and degradation products of afoxolaner generated by stress degradation of afoxolaner bulk drug substance under various stress conditions. This method was also successfully validated as per the current ICH guidelines for afoxolaner and Q6S07 (afoxolaner related substance) with respect to specificity, linearity (R² > 0.999), detection limit (∼0.21 µg/mL), quantitation limit (∼0.70 µg/mL), accuracy, precision, and robustness. Due to its speed, high degree of selectivity, and accuracy, the proposed method is suitable and highly desirable in quality control laboratories for routine analysis of afoxolaner.

Acaricidal and Repellent Effects of Essential Oils against Ticks: A Review

Tick control is a priority in order to prevent the transmission of vector-borne diseases. Industrial chemical acaricides and repellents have been the most efficient tools against hard ticks for a long time. However, the appearance of resistances has meant the declining effectiveness of the chemicals available on the market. The trend today is to develop alternative control methods using natural products to replace nonefficient pesticides and to preserve the efficient ones, hoping to delay resistance development. Traditional in vitro evaluation of acaricidal activity or resistance to synthetic pesticides have been reviewed and they mainly focus on just one species, the one host tick (Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)). Recent reports have called for the standardization of natural product components, extraction techniques, and experimental design to fully discover their acaricidal potential. This study reviews the main variables used in the bibliography about the efficiency of natural products against ticks, and it proposes a unification of variables relating to ticks, practical development of bioassays, and estimation of ixodicidal activity.

Heartworm disease - Overview, intervention, and industry perspective

Dirofilaria immitis, also known as heartworm, is a major parasitic threat for dogs and cats around the world. Because of its impact on the health and welfare of companion animals, heartworm disease is of huge veterinary and economic importance especially in North America, Europe, Asia and Australia. Within the animal health market many different heartworm preventive products are available, all of which contain active components of the same drug class, the macrocyclic lactones. In addition to compliance issues, such as under-dosing or irregular treatment intervals, the occurrence of drug-resistant heartworms within the populations in the Mississippi River areas adds to the failure of preventive treatments. The objective of this review is to provide an overview of the disease, summarize the current disease control measures and highlight potential new avenues and best practices for treatment and prevention.

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.

AC-DC electropenetrography: fundamentals, controversies, and perspectives for arthropod pest management

Studying the intimate association of arthropods with their physical substrate is both important and challenging. It is important because substrate is a key determinant for organism fitness; challenging because the intricacies of this association are dynamic, and difficult to record and resolve. The advent of electropenetrography (EPG) and subsequent developments allowed researchers to overcome this challenge. Nonetheless, EPG research has been historically restricted to piercing-sucking hemipteran plant pests. Recently, its potential use has been greatly broadened for additional pests with instrument advances. Thus, blood-feeding arthropods and chewing feeders, as well as non-feeding behaviors like oviposition by both pests and parasitoids, are novel new targets for EPG research, with critical consequences for integrated pest management. EPG can explain mechanisms of crop damage, plant or animal pathogen transmission, and the effects of insecticides, antifeedants, repellents, or transgenic plants and animals, on specific behaviors of damage or transmission. This review broadly covers the principles and development of EPG technology, emphasizing controversies and challenges remaining with suggested research to overcome them. In addition, it summarizes 60+ years of basic and applied EPG research, and previews future directions for pest management. The goal is to stimulate new applications for this unique enabling technology. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

The molecular targets of ivermectin and lotilaner in the human louse Pediculus humanus humanus: New prospects for the treatment of pediculosis

Control of infestation by cosmopolitan lice (Pediculus humanus) is increasingly difficult due to the transmission of parasites resistant to pediculicides. However, since the targets for pediculicides have no been identified in human lice so far, their mechanisms of action remain largely unknown. The macrocyclic lactone ivermectin is active against a broad range of insects including human lice. Isoxazolines are a new chemical class exhibiting a strong insecticidal potential. They preferentially act on the γ-aminobutyric acid (GABA) receptor made of the resistant to dieldrin (RDL) subunit and, to a lesser extent on glutamate-gated chloride channels (GluCls) in some species. Here, we addressed the pediculicidal potential of isoxazolines and deciphered the molecular targets of ivermectin and the ectoparasiticide lotilaner in the human body louse species Pediculus humanus humanus. Using toxicity bioassays, we showed that fipronil, ivermectin and lotilaner are efficient pediculicides on adult lice. The RDL (Phh-RDL) and GluCl (Phh-GluCl) subunits were cloned and characterized by two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes. Phh-RDL and Phh-GluCl formed functional homomeric receptors respectively gated by GABA and L-glutamate with EC₅₀ values of 16.0 μM and 9.3 μM. Importantly, ivermectin displayed a super agonist action on Phh-GluCl, whereas Phh-RDL receptors were weakly affected. Reversally, lotilaner strongly inhibited the GABA-evoked currents in Phh-RDL with an IC₅₀ value of 40.7 nM, whereas it had no effect on Phh-GluCl. We report here for the first time the insecticidal activity of isoxazolines on human ectoparasites and reveal the mode of action of ivermectin and lotilaner on GluCl and RDL channels from human lice. These results emphasize an expected extension of the use of the isoxazoline drug class as new pediculicidal agents to tackle resistant-louse infestations in humans.

Human cosmopolitan lice are responsible for pediculosis, which represent a significant public health concern. Resistant lice against insecticides and lack of safety of the treatments for human and environment is a growing issue worldwide. Here we investigated the efficacy on lice of the classical macrocyclic lactone drug, ivermectin, and of the isoxazoline drug, lotilaner. This study was done to decipher their mode of action at the molecular and functional levels in order to propose new strategies to control lice infestation. Our bioassay results indicate that ivermectin and lotilaner were potent at killing human adult lice, with lotilaner showing a higher efficacy than ivermectin. Furthermore, we identified and pharmacologically characterized the first glutamate- and GABA-gated chloride channels ever described in human lice yet. Mechanistically, our molecular biology and electrophysiology findings demonstrate that ivermectin acted preferentially at glutamate channels, while lotilaner specifically targeted GABA channels. These results provide new insights in the understanding of the insecticide mode of action and highlight the potential of isoxazolines as a new alternative for the treatment of human lice.

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

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

Endectocides as a complementary intervention in the malaria control program: a systematic review

BACKGROUND

Malaria is the most common vector-borne disease transmitted to humans by Anopheles mosquitoes. Endectocides and especially ivermectin will be available as a vector control tool soon. The current review could be valuable for trial design and clinical studies to control malaria transmission.

METHODS

PubMed/MEDLINE, Scopus, Web of Science, and Science Direct were searched for original English published papers on ("Malaria chemical control" OR "Malaria elimination" OR "Anopheles vector control" OR "Malaria zooprophylaxis") AND ("Systemic insecticides" OR "Endectocides" OR "Ivermectin"). The last search was from 19 June 2019 to 31 December 2019. It was updated on 17 November 2020. Two reviewers (SG and FGK) independently reviewed abstracts and full-text articles. Data were extracted by one person and checked by another. As meta-analyses were not possible, a qualitative summary of results was performed.

RESULTS

Thirty-six published papers have used systemic insecticides/endectocides for mosquito control. Most of the studies (56.75%) were done on Anopheles gambiae complex species on doses from 150 μg/kg to 400 μg/kg in several studies. Target hosts for employing systemic insecticides/drugs were animals (44.2%, including rabbit, cattle, pig, and livestock) and humans (32.35%).

CONCLUSIONS

Laboratory and field studies have highlighted the potential of endectocides in malaria control. Ivermectin and other endectocides could soon serve as novel malaria transmission control tools by reducing the longevity of Anopheles mosquitoes that feed on treated hosts, potentially decreasing Plasmodium parasite transmission when used as mass drug administration (MDA).

Status and outlook for acaricide and insecticide discovery

To guarantee sustainability and progress, the agrochemical industry is faced with several major challenges. Currently, loss of active ingredients due to consumer perception, changing grower needs and ever-changing regulatory requirements is far higher than the number being introduced into the market. Therefore, there is a need to develop new products that can provide improved efficacy, selectivity and favorable environmental profiles. Strategies to achieve these goals are the search for acaricides and insecticides with new modes of action, or the discovery of novel molecules with activity on the most attractive target sites having resistance breaking properties against pest species. In this context, the introduction of halogen atoms or asymmetric centers into an active ingredient remains an important tool to modulate their properties, but so too is the pro-pesticide concept. This review gives an overview of agrochemicals launched over the past 8 years, reflects new insights into known mechanisms of action, and describes the status and outlook for acaricide and insecticide discovery.

Design, Synthesis, and Insecticidal Activity of 5,5-Disubstituted 4,5-Dihydropyrazolo[1,5-a]quinazolines as Novel Antagonists of GABA Receptors

To control the development of resistance to conventional insecticides acting as γ-aminobutyric acid (GABA) receptor antagonists (e.g., fipronil), new GABAergic 5,5-disubstituted 4,5-dihydropyrazolo[1,5-a]quinazolines were designed via a scaffold-hopping strategy and synthesized with a facile method. Among the 50 target compounds obtained, compounds 5a, 5b, 7a, and 7g showed excellent insecticidal activities against a susceptible strain of Plutella xylostella (LC₅₀ values ranging from 1.03 to 1.44 μg/mL), which were superior to that of fipronil (LC₅₀ = 3.02 μg/mL). Remarkably, the insecticidal activity of compound 5a was 64-fold better than that of fipronil against the field population of fipronil-resistant P. xylostella. Electrophysiological studies against the housefly GABA receptor heterologously expressed in Xenopus oocytes indicated that compound 5a could act as a potent GABA receptor antagonist, and IC₅₀ was calculated to be 32.5 nM. Molecular docking showed that the binding poses of compound 5a with the housefly GABA receptor can be different compared to fipronil, which explains the effectiveness of compound 5a against fipronil-resistant insects. These findings have suggested compound 5a as a lead compound for a novel GABA receptor antagonist controlling field-resistant insects and provided a basis for further design, structural modification, and development of 4,5-dihydropyrazolo[1,5-a]quinazoline motifs as new insecticidal GABA receptor antagonists.

Discovery, development, chemical diversity and design of isoxazoline-based insecticides

Isoxazoline is a 5-membered heterocycle present in the active compounds of many commercial veterinary anti-ectoparasitic products. The molecular target of isoxazolines is the inhibition of GABA-gated chloride channels in insects. These facts have inspired the use of the isoxazoline scaffold in the design of novel insecticide compounds. The main strategies used for isoxazoline synthesis are either the 1,3-dipolar cycloaddition between a nitrile oxide and an alkene or the reaction between hydroxylamine and an α,β-unsaturated carbonyl compound. This review highlights the utilization of isoxazoline as insecticide: its mode of action, its commercial preparations and its consideration in the design of novel insecticides. Similarity analyses were performed with 235 isoxazoline derivatives in three different cheminformatic approaches - chemical property correlations, similarity network and compound clustering. The cheminformatic methodologies are interesting tools to use in evaluating the similarity between commercial isoxazolines and to clarify the main features explored within their derivatives.

2-Isoxazolines: A Synthetic and Medicinal Overview

Isoxazolines are nitrogen- and oxygen-containing five-membered heterocyclic scaffolds with extensive biological activities. This framework can be readily obtained in good to excellent yields through 1,3-dipolar cycloaddition between nitrones with alkynes or allenes, aryl/alkyl halides, alkynes, and oxaziridines under mild conditions. This scaffold has been an emerging area of interest for many researchers given their wide range of bioactivities. Herein we review synthetic strategies toward isoxazolines and the role these efforts have had in enhancing the biological activity of natural products and synthetic compounds such as antitubercular agents, COX-1 inhibitors, COX-2 inhibitors (e. g., valdecoxib), nicotinic receptor modulators, and MIF inhibitors. With a focus on efforts from 2010 onward, this review provides in-depth coverage of the design and biological evaluation of isoxazoline systems and their impact on various pathologies.

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.

Recent Advancements in the Control of Cat Fleas

Simple Summary

The cat flea Ctenocephalides felis felis is the most important pest of domesticated cats and dogs worldwide. This review covers the recent advancements in the control of cat fleas. Over the years, there has been an interest in using ecologically friendly approaches to control fleas. To date, no biological, natural, or cultural means have been discovered that mitigate flea infestations. The recent registration of novel topical and oral therapies promises a new revolution in the control of fleas and ticks and the diseases associated with them.

Abstract

With the advent of imidacloprid and fipronil spot-on treatments and the oral ingestion of lufenuron, the strategies and methods to control cat fleas dramatically changed during the last 25 years. New innovations and new chemistries have highlighted this progress. Control strategies are no longer based on the tripartite approach of treating the pet, the indoor environment, and outdoors. The ability of modern therapies to break the cat flea life cycle and prevent reproduction has allowed for the stand-alone treatments that are applied or given to the pet. In doing so, we have not only controlled the cat flea, but we have prevented or reduced the impact of many of the diseases associated with ectoparasites and endoparasites of cats and dogs. This review provides an update of newer and non-conventional approaches to control cat fleas.

Current Contributions of Organofluorine Compounds to the Agrochemical Industry

Currently, more than 1,200 agrochemicals are listed and many of these are regularly used by farmers to generate the food supply to support the expanding global population. However, resistance to pesticides is an ever more frequently occurring phenomenon, and thus, a continuous supply of novel agrochemicals with high efficiency, selectivity, and low toxicity is required. Moreover, the demand for a more sustainable society, by reducing the risk chemicals pose to human health and by minimizing their environmental footprint, renders the development of novel agrochemicals an ever more challenging undertaking. In the last two decades, fluoro-chemicals have been associated with significant advances in the agrochemical development process. We herein analyze the contribution that organofluorine compounds make to the agrochemical industry. Our database covers 424 fluoro-agrochemicals and is subdivided into several categories including chemotypes, mode of action, heterocycles, and chirality. This in-depth analysis reveals the unique relationship between fluorine and agrochemicals.

Diagnosis and treatment of demodicosis in dogs and cats: Clinical consensus guidelines of the World Association for Veterinary Dermatology

BACKGROUND

Demodicosis is a common disease in small animal veterinary practice worldwide with a variety of diagnostic and therapeutic options.

OBJECTIVES

To provide consensus recommendations on the diagnosis, prevention and treatment of demodicosis in dogs and cats.

METHODS AND MATERIALS

The authors served as a Guideline Panel (GP) and reviewed the literature available before December 2018. The GP prepared a detailed literature review and made recommendations on selected topics. A draft of the document was presented at the North American Veterinary Dermatology Forum in Maui, HI, USA (May 2018) and at the European Veterinary Dermatology Congress in Dubrovnik, Croatia (September 2018) and was made available via the World Wide Web to the member organizations of the World Association for Veterinary Dermatology for a period of three months. Comments were solicited and responses were incorporated into the final document.

CONCLUSIONS

In young dogs with generalized demodicosis, genetic and immunological factors seem to play a role in the pathogenesis and affected dogs should not be bred. In old dogs and cats, underlying immunosuppressive conditions contributing to demodicosis should be explored. Deep skin scrapings are the diagnostic gold standard for demodicosis, but trichograms and tape squeeze preparations may also be useful under certain circumstances. Amitraz, macrocyclic lactones and more recently isoxazolines have all demonstrated good efficacy in the treatment of canine demodicosis. Therapeutic selection should be guided by local drug legislation, drug availability and individual case parameters. Evidence for successful treatment of feline demodicosis is strongest for lime sulfur dips and amitraz baths.

Evaluation of a topical sarolaner-selamectin combination to control flea populations on naturally infested cats in private residences in West Central Florida

Historic data show that home flea infestations can be managed by treating all animals on the premises with a highly effective flea control product. The use of effective products has also been shown to reduce pruritus and minimize dermatologic lesions in both cats and dogs. Therefore, an in-home study was conducted in West Central Florida USA to evaluate the efficacy of a topically applied selamectin-sarolaner formulation to control fleas in naturally infested cats over a 12-week period. Thirty-seven cats in 21 households were treated once monthly with the selamectin-sarolaner topical solution. In the topical fluralaner treatment (positive control) group, forty-three cats in 20 households were treated once on day 0. A combined total of thirty dogs in both groups were treated once monthly with oral sarolaner. Fleas on cats were counted by flea combing, fleas on dogs were counted using visual area counts and fleas in the indoor premises were assessed using intermittent-light flea traps. Blinded-assessments of feline dermatologic lesions (modified-SCORFAD) were conducted monthly by a boarded-dermatologist and pruritus severity was evaluated by pet owners. Three consecutive monthly treatments of selamectin-sarolaner reduced flea populations on cats by 96.3 % within 7 days and by 100% from week 6 to the end of the 12-week study. The topical application of fluralaner reduced flea populations by 98.1 % within 7 days and efficacy reached 100% by week 12. At the end of the study, fleas were completely eradicated (from cats, dogs and homes) in every home regardless of treatment group. Owner reported cat pruritus was reduced by > 87 % in both treatment groups by week 12. Significant improvements in dermatologic lesion scores (> 81 %) were achieved by both products by the end of the study. Monthly applications of topical selamectin-sarolaner or topical fluralaner to cats living in the heavy flea challenge environment of West Central Florida USA were effective in eradicating flea infestations, reducing pruritus and improving dermatologic lesions.

A single oral dose of fluralaner (Bravecto®) in dogs rapidly kills 100% of blood-fed Phlebotomus perniciosus, a main visceral leishmaniasis vector, for at least 1 month after treatment

Dogs are the reservoir host of zoonotic visceral leishmaniasis (VL) caused by Leishmania infantum (Kinetoplastida: Trypanosomatidae). Both subclinically-infected and sick animals can be infectious to competent phlebotomine vectors. The degree and duration of insecticidal efficacy of an oral dose of fluralaner (Bravecto®; Merck Animal Health) was determined in dogs exposed to bites of Phlebotomus perniciosus (Diptera: Psychodidae), a main Mediterranean vector of VL. Twelve dogs allocated to two groups of six animals each were included in a parallel-group designed, negative-controlled, randomized, blinded, single-centre efficacy study. Group 2 was treated with fluralaner on day 0, and sand-fly exposure of both groups was performed on days 1, 28 and 84. Viability of blood-fed females was assessed up to 96 h after exposure and efficacy was measured as the survival rate of specimens fed on Group 2 versus those fed on Group 1. A mortality of 100% was recorded at 24 h in females fed on Group 2 at both days 1 and 28. Significant insecticidal efficacy was still observed on day 84, with > 50% mortality recorded by 48 h post blood meal in Group 2. Fluralaner treatment of dogs represents a promising and affordable method for reducing the pool of infected vectors in endemic settings of zoonotic VL.

[2 + 2 + 1] Heteroannulation of Alkenes with Enynyl Benziodoxolones and Silver Nitrite Involving C≡C bond Oxidative Cleavage: Entry to 3-Aryl-Δ2-isoxazolines

A copper-catalyzed [2 + 2 + 1] heteroannulation of alkenes with enynyl benziodoxolones and AgNO₂ involving oxidative cleavage of the C≡C bond promoted by cooperative Zn(OTf)₂, KOAc, and 4 Å MS for producing 3-aryl Δ²-isoxazolines is reported. Mechanistic studies indicate that AgNO₂ serves as the N/O two-atom unit source, enabling the formation of three bonds through NO₂ addition across the C≡C bond, NO-transfer, C≡C bond cleavage, and annulation cascades.

Ctenocephalides felis (cat flea) infestation in neonatal dairy calves managed with deltamethrin pour-on in Australia

Ctenocephalides felis infestations outbreak is documented as a welfare and production limiting disease in neonatal calves in eastern New South Wales, Australia. Due to the calves' discomfort, the first objective was to relieve the calves from the large burden of fleas. The affected neonatal 0-4 week old calves showed dull and quiet demeanour, with the geometric mean of body condition score (BCS) 2.67 (2-4) and geometric mean burden 41.51 (15-75) of fleas collected over 3 min. Deltamethrin pour-on (Arrest Easy-Dose, Virbac Animal Health, Australia) registered for treatment of lice and flies on cattle in Australia was evaluated for control effect of the cat flea (C. felis) on cattle. The fleas were identified morphologically as being C. felis which was confirmed by sequencing cytochrome c oxidase I gene (cox1). We report successful improvement of welfare and reduction of flea counts post application of pour-on deltamethrin on the property. In the absence of registered flea product for cattle in Australia, deltamethrin pour-on product is a suitable option, because of its registration for control of lice and flies on cattle.

Efficacy of lotilaner (Credelio™) against the adult cat flea, Ctenocephalides felis and flea eggs following oral administration to dogs

BACKGROUND

A blinded, randomized, negative controlled laboratory study was conducted to evaluate the efficacy of lotilaner (CredelioTM, Elanco) when administered orally to dogs, against experimentally induced adult flea infestations and flea egg production.

METHODS

Twenty dogs were selected for the study and allocated to two treatment groups. Ten dogs were treated with lotilaner (at the lower half of the recommended dose range of 20-43 mg/kg) on Day 0. Ten dogs treated with placebo tablets served as the control group. Each dog was infested with 100 unfed adult C. felis fleas on days -1, 6, 13, 20 and 29. At 24 h post-treatment or post-infestation, each dog was combed for the removal and counting of adult live fleas. Flea eggs were also collected and counted from the pan under each dog cage.

RESULTS

Dogs in the lotilaner treated group received a mean dose of 22.6 mg/kg (range 20.2-25.9 mg/kg) and no adverse events were observed in any dog in this study. At each evaluation time point, the lotilaner group provided 100% efficacy against adult live flea counts as compared to the placebo control group. Egg production from lotilaner treated dogs was reduced by 98.5% (geometric mean; 97.4% arithmetic mean) 24 h post-treatment (and 48 h post-flea infestation). No eggs (100% efficacy) were available for collection following infestations on Day 6 onwards from the lotilaner treated dogs. At each evaluation time point, adult live flea counts from the lotilaner treated dogs were significantly lower (P < 0.0001) than from the placebo control group.

CONCLUSIONS

In dogs treated with a single dose of lotilaner (mean dose 22.6 mg/kg), 100% of adult fleas were killed within 24 h post-treatment or post-subsequent infestations as compared to the placebo control group, thereby demonstrating that lotilaner kills fleas before they can lay eggs thus preventing subsequent flea infestations for 30 days after treatment. There were no reported adverse events in any dogs, demonstrating that lotilaner tablets were well tolerated at the dose rates assessed in this study.

A three-component approach to isoxazolines and isoxazoles under metal-free conditions

A 1,3-dipolar cycloaddition of 2-methylquinoline, tert-butyl nitrite (TBN) and alkynes or alkenes for the synthesis of biheteroaryls containing both isoxazoline/isoxazole and quinoline motifs has been developed. In this protocol, TBN serves as a convenient N-O source to convert 2-methylquinoline into intermediate nitrile oxides in situ.

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.

Suspected neurological toxicity after oral application of fluralaner (Bravecto®) in a Kooikerhondje dog

Background

Although the new isoxazoline drug fluralaner (Bravecto®) is generally well tolerated in dogs, adverse drug reactions involving neurological dysfunction occurred in individual dogs. However, most of these cases are documented inadequately and none of them is reported and discussed in the literature. As isoxazoline drugs target neuronal chloride channels with a clear preference for invertebrates, they are considered to have a good safety profile. However, pharmacodynamic effects in the nervous system of vertebrates cannot be ruled out completely.

Case presentation

A seven-month-old female Kooikerhondje dog was treated with Bravecto® at the recommended dose. About 24 h after administration, the dog exhibited signs of neurological toxicity, including generalized ataxia, myoclonic jerks, tremor of head and body, muscle twitching and oral dysphagia. All symptoms were transient and the dog fully recovered without any treatment after 10 h.

Conclusion

This case report describes transient occurrence of neurological dysfunction after administration of Bravecto®. It may help to better classify adverse drug reactions after application of isoxazoline drugs and documents a good prognosis even after occurrence of severe neurological dysfunction in the present case.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-2016-4) contains supplementary material, which is available to authorized users.

The treatment of sarcoptic mange in wildlife: a systematic review

BACKGROUND

Sarcoptic mange, caused by the Sarcoptes scabiei mite, is an infectious disease of wildlife, domestic animals and humans with international importance. Whilst a variety of treatment and control methods have been investigated in wildlife, the literature is fragmented and lacking consensus. The primary objectives of this review were to synthesise the diverse literature published on the treatment of sarcoptic mange in wildlife from around the world, and to identify the qualities of successful treatment strategies in both captive and free-roaming wildlife.

METHODS

A systematic search of the electronic databases CAB Direct, PubMed, Scopus, Web of Science, EMBASE and Discovery was undertaken. Data pertaining to study design, country, year, species, study size, mange severity, treatment protocol and outcomes were extracted from eligible studies and placed in a table. Following data extraction, a decision tree was used to identify studies suitable for further analysis based on the effectiveness of their treatment protocol, whether they were conducted on captive or non-captive wildlife, and the quality of their post-treatment monitoring period.

RESULTS

Twenty-eight studies met our initial inclusion criteria for data collection. Of these studies, 15 were selected for further analysis following application of the decision tree. This comprised of 9 studies on captive wildlife, 5 studies on free-living wildlife and 1 study involving both captive and free-living wildlife. Ivermectin delivered multiple times via subcutaneous injection at a dose between 200-400 µg/kg was found to be the most common and successfully used treatment, although long-term data on post-release survival and re-infection rates was elusive.

CONCLUSIONS

To our knowledge, this review is the first to demonstrate that multiple therapeutic protocols exist for the treatment of sarcoptic mange in wildlife. However, several contemporary treatment options are yet to be formally reported in wildlife, such as the use of isoxazoline chemicals as a one-off treatment. There is also a strong indication for more randomised controlled trials, as well as improved methods of post-treatment monitoring. Advancing this field of knowledge is expected to aid veterinarians, wildlife workers and policy makers with the design and implementation of effective treatment and management strategies for the conservation of wildlife affected by sarcoptic mange.

3,3-Diazidoenones – new types of highly reactive bis-azides. Preparation and synthetic transformations

A new family of highly reactive 3,3-diazidoenones was obtained. Their chemistry was investigated by both experimental studies and DFT calculations.

Current status of chirality in agrochemicals

The agrochemical industry is searching continuously for new pesticides to develop products that have optimal efficacy, lower application rates in the field, increased selectivity, favourable toxicological and environmental safety, enhanced user friendliness and better economic viability. One strategy by which to achieve these ambitious goals makes use of the unique properties of molecules containing asymmetric centres. In the past, many natural products and their congeners have been a source of inspiration in the design of new active ingredients, and the molecular structures of the resulting compounds have become increasingly complex; some 30% contain fragments with asymmetric centres. However, despite enormous progress in catalytic asymmetric processes over the past decade, few agrochemicals are produced in an enantiomerically pure or enriched form on an industrial scale. Since 2007, ∼ 43% of the 44 products launched (insecticides, acaricides, fungicides, nematicides and herbicides) contain one or more asymmetric centres in the molecule (∼ 47%) and most have been launched as racemic mixtures of enantiomers or diastereomers. This review provides an overview of the current status of chiral agrochemicals launched over the past 10 years and describes the inherently connected challenges of modern agricultural chemistry by managing important aspects resulting from the stereochemistry of these innovative products. © 2018 Society of Chemical Industry.

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.

Repurposing isoxazoline veterinary drugs for control of vector-borne human diseases

Isoxazolines are oral insecticidal drugs currently licensed for ectoparasite control in companion animals. Here we propose their use in humans for the reduction of vector-borne disease incidence. Fluralaner and afoxolaner rapidly killed Anopheles, Aedes, and Culex mosquitoes and Phlebotomus sand flies after feeding on a drug-supplemented blood meal, with IC50 values ranging from 33 to 575 nM, and were fully active against strains with preexisting resistance to common insecticides. Based on allometric scaling of preclinical pharmacokinetics data, we predict that a single human median dose of 260 mg (IQR, 177-407 mg) for afoxolaner, or 410 mg (IQR, 278-648 mg) for fluralaner, could provide an insecticidal effect lasting 50-90 days against mosquitoes and Phlebotomus sand flies. Computational modeling showed that seasonal mass drug administration of such a single dose to a fraction of a regional population would dramatically reduce clinical cases of Zika and malaria in endemic settings. Isoxazolines therefore represent a promising new component of drug-based vector control.

A randomized, controlled field study to assess the efficacy and safety of lotilaner (Credelio™) in controlling fleas in client-owned cats in Europe

BACKGROUND

Lotilaner is a new isoxazoline developed as an oral ectoparasiticide for cats and dogs. Its safety, rapid killing onset of action and sustained speed of fleas and ticks kill for a minimum of one month after administration, were demonstrated in a number of laboratory studies in cats. This study was performed to demonstrate the efficacy and safety of lotilaner flavored chewable tablets for cats (Credelio™, Elanco) in controlling fleas under field conditions in European countries.

METHODS

Seventeen veterinary practices in France and Spain, located in high flea prevalence regions, participated in the study. Households with a maximum of three cats and two dogs were randomized 2:1 to a lotilaner (minimum dose rate 6 mg/kg) or a topical fipronil/(S)-methoprene combination (Frontline Combo® Spot-on Cats, Merial) group (administered according to label). In each household, efficacy against fleas and flea allergy dermatitis (FAD) signs were assessed in one primary cat (bearing a minimum of five fleas on Day 0) while safety was evaluated in all cats. There were 121 households included in the lotilaner and 61 in the fipronil/(S)-methoprene groups, respectively. Treatments were administered by the cats' owners on Day 0. Flea counts and FAD assessments were made on Days 0, 14, and 28. Efficacy calculations were based on geometric mean percent reductions of live flea counts versus baseline pre-treatment counts.

RESULTS

Lotilaner efficacy was 97.2 and 98.1% on Days 14 and 28, respectively. Corresponding efficacy for fipronil/(S)-methoprene was 48.3 and 46.4%. Lotilaner was superior to fipronil/(S)-methoprene at all post-Day 0 assessments and over the whole study period (P < 0.0001). At every post-administration evaluation, at least 81% of lotilaner-treated cats were flea-free as opposed to 25% in the fipronil/(S)-methoprene group. Lotilaner improved or eliminated clinical signs of FAD, including pruritus. Both products were well tolerated.

CONCLUSIONS

Under field conditions in Europe, lotilaner flavored chewable tablets for cats displayed an efficacy against fleas higher than 97%; clinical signs of FAD were improved or eliminated. Lotilaner tablets were safe and provided superior flea control to fipronil/(S)-methoprene.

Laboratory evaluation of the efficacy and speed of kill of lotilaner (CredelioTM) against Ixodes ricinus ticks on cats

BACKGROUND

Lotilaner, approved for dogs as a chewable tablet formulation, has separately been developed for oral use in cats (CredelioTM chewable tablets for cats), to meet the need for an easy to use, safe and rapidly effective parasiticide. It is a valid cat- and owner-friendly alternative to topical products. This manuscript describes three pivotal laboratory studies assessing the efficacy and speed of kill of lotilaner in cats against Ixodes ricinus ticks following a single oral administration, at a dose rate close to 6 mg/kg.

METHODS

In Studies 1 and 2, efficacy and safety were evaluated 48 h after treatment and post-treatment weekly infestations in 16 cats, against untreated controls, for 35 days. In Study 3, efficacy and safety were assessed in 8 lotilaner-treated cats until Day 35, before and after 24 h incubation of the female live ticks removed from the animals 12, 18 and 24 h after dosing and subsequent weekly infestations.

RESULTS

Efficacy was > 99% on days 23 and 37, and 100% on all other timepoints in Study 1. In Study 2 it was > 98% on Days 9 and 37, and 100% on all other days. In Study 3, on Day 0, lotilaner was > 90% efficacious, pre- and post-incubation at all time-points. On Day 7, at 12 hours after infestation, efficacy was 100%, pre- and post-incubation. On Day 14, there was a 66.5% reduction in geometric mean live tick counts in treated cats compared to controls, increasing, after incubation, to 94.4%. Afterwards, efficacy decreased below 90% while tick counts in the treated groups remained significantly lower compared to controls. At 18 hours, lotilaner was ≥ 90% efficacious through Day 37, increasing to 100% at 24 hours, on all study days, with the exception of Day 28 (98.9 and 99.1% pre- and post-incubation, respectively). There were no treatment-related adverse events.

CONCLUSIONS

At the minimum dose rate of 6 mg/kg, lotilaner was efficacious against I. ricinus ticks. In addition, lotilaner was effective against this tick within 12 hours of treatment, reaching 100% efficacy within 24 hours. Lotilaner sustained a rapid kill of newly infesting I. ricinus through 35 days. By quickly killing ticks that infest cats, lotilaner has the potential to contribute to the reduction of tick-borne pathogens transmission.