Efficacy of dinotefuran, permethrin and pyriproxyfen combination spot-on on dogs against Phlebotomus perniciosus and Ctenocephalides canis

Laboratory evidence that dinotefuran, pyriproxyfen and permethrin combination abrogates Leishmania infantum transmissibility by sick dogs

Dogs are reservoir hosts of leishmaniasis caused by Leishmania infantum and transmitted by phlebotomine vectors. The effect of dinotefuran, pyriproxyfen and permethrin spot-on solution (Vectra®3D, Ceva Santé Animale, Libourne, France) on Leishmania transmissibility by naturally infected dogs via reared Phlebotomus perniciosus, was assessed. Dogs affected by leishmaniasis were submitted to xenodiagnosis and 6 infecting >10% of insects were treated topically on day 0. Antifeeding, insecticidal and anti-transmissibility effects were evaluated through xenodiagnoses performed on days 1, 7 and 28, using individual pre-treatment parameters as control. Feeding and mortality rates were assessed at 24 h, whereas promastigote infection, maturation and burden were assessed up to 96 h post blood meal (potentially infectious rate). On day 1, the anti-feeding efficacy was >95% in 4 dogs, insecticidal efficacy 100% in 4 dogs, and anti-transmissibility effect 100% in 6 dogs. Efficacy rates recorded on day 7 were very similar to day 1. On day 28, anti-feeding and insecticidal efficacy values were much broader, ranging 32.6-100% and 7.7-94.4%, respectively. Potentially infectious insects were recorded from two dogs, with sharp decrease in transmissibility rate as compared with pre-treatment condition. Altogether, Vectra®3D abrogated by >98% the potential Leishmania transmissibility by the examined pool of infected dogs over 1 month.

Pharmacokinetics of combination antiparasitic drug preparation for dogs and cats in the form of spot-on solution

Objective:

The object of the study was to examine the major pharmacokinetic parameters after a single application of a complex drug preparation for veterinary use based on fipronil, praziquantel, moxidectin, and pyriproxyfen in cats and dogs.

Materials and Methods:

For dogs, the drug preparation was administered spot-on solution in the following dosage of active pharmaceutical substances: fipronil 27.0 mg/kg body weight (bwt), praziquantel 10.8 mg/kg bwt, moxidectin 6.75 mg/kg bwt, and pyriproxyfen 5.4 mg/kg bwt; for cats, the dosage was the following: fipronil 43.2 mg/kg bwt, praziquantel 17.28 mg/kg bwt, moxidectin 4.32 mg/kg bwt, and pyriproxyfen 8.64 mg/kg bwt. The blood samples were taken from dogs and cats. The principle of the method for determining praziquantel, trans-4-hydroxypraziquantel, pyriproxyfen, and fipronil in serum samples was chromatographed in a high-pressure liquid chromatograph with detection by means of a mass-spectrometric detector. The moxidectin content of the blood was detected by high-performance liquid chromatography.

Results:

The drug preparation active substances: praziquantel, fipronil, and moxidectin are absorbed into the blood of dogs and cats. The penetration of praziquantel into the systemic circulation and further into organs and tissues was proved. After topical administration, moxidectin is absorbed and distributed systemically and is slowly removed from the plasma, which manifests itself in detectable concentrations of moxidectin in the blood for 1 month.

Conclusion:

The present results of pharmacokinetic investigations may promote to the determination of effective therapy strategy and prophylaxis of parasitic diseases in dogs and cats.

Controlling phlebotomine sand flies to prevent canine Leishmania infantum infection: A case of knowing your enemy

Leishmaniosis caused by Leishmania infantum is a widespread zoonotic disease that can be transmitted to animals and humans by their vectors, blood-sucking phlebotomine sand flies. To prevent canine leishmaniosis across the whole Mediterranean region, vector control is essential. Because of phlebotomine breeding sites are diverse, environmental larval controls have limited practical value. Control methods of adults are being evaluated, such as selective baits based on sugar feeding of males and females or Attractive Toxic Sugar Baits (ATSB), and the indoor use of Long-Lasting-Insecticidal Nets (LLINs) treated with permethrin to prevent sand fly bites complementing the Indoor Residual Spraying (IRS) approach suggested by WHO. Although several strategies exist, the best control measure to prevent canine Leishmania infantum is to treat dogs using biocidal topical formulations based on legal insecticides (PTs18) or repellents (PTs19) (as collars, spot-ons and/or sprays) during the period when the vectors are active. This means we need to really know the biology and life cycle of the sand fly vector. According to available data, by mapping ambient temperatures we can already predict high risk areas where vector densities will be higher. In ongoing research, new candidates are emerging to fight against sand flies including natural plant extracts with low impacts on the environment and host animal. Other options in the future could be systemic insecticides to help reduce sand fly populations in high density areas. In parallel, health authorities and professionals involved in animal and public health (veterinarians, physicians, entomologists and epidemiologists) must work together in a One Health approach to minimize Leishmania infection. Veterinarians play a crucial role in liaising between key stake holders and dog owners to ensure the latter act responsibly in using repellents as a preventive measure against sand fly bites.

Laboratory assessment of the anti-feeding effect for up to 12 months of a slow release deltamethrin collar (Scalibor®) against the sand fly Phlebotomus perniciosus in dogs

Background

Leishmaniosis/leishmaniasis consists of a wide group of diseases, caused by different Leishmania species and having different hosts. Leishmaniosis caused by Leishmania infantum, a disease primarily of dogs and humans, occurs after susceptible hosts are exposed to the feeding behavior of infected sand flies. A one-year laboratory study in dogs was designed to determine the 364-day anti-feeding efficacy of a slow release deltamethrin collar against the sand fly P. perniciosus, a common host of L. infantum in the Mediterranean basin.

Methods

In this assessor-blinded study, 16 Beagle dogs were randomized into two groups using P. perniciosus engorgement rates from a Day -7 challenge. On Day 0, dogs in Group 1 received a placebo collar, while dogs in Group 2 received a deltamethrin collar (Scalibor® Protector Band). All dogs were caged, sedated and then exposed for 1 h to 85 (± 10) female and 15 (± 5) male P. perniciosus on Day 7 and every 28 days through Day 364. All flies, alive and dead, were aspirated from cages and from dogs, immediately counted and then frozen for assessment of blood engorgement. Anti-feeding efficacy was determined by comparing the arithmetic means of engorged female flies (alive, dead and moribund) in the deltamethrin group to the control group means. Insecticidal efficacy at the time flies were retrieved was assessed by comparisons between groups of mean live female fly counts.

Results

In the deltamethrin group, relative to the control group, there was a significant reduction in arithmetic mean numbers of engorged P. perniciosus of 94–98% from Day 7 through Day 364. On Day 28, in the treated group relative to the control group, there was a 74% reduction in mean live fly counts, with between-group differences significant from Days 7 through 196, although insecticidal activity remained less than 50% from Day 56.

Conclusion

Deltamethrin collar application to dogs reduced sand fly feeding by ≥ 94%, relative to unprotected control dogs, for 364 days. Thus, one collar applied to a dog can prevent or reduce the risk of sand fly transmission of Leishmania for one full year.

Permethrin enhances the agonist activity of dinotefuran on insect cholinergic synaptic transmission and isolated neurons

Insect resistance mechanisms against pesticides lead to the development and the search of new pesticide combinations in order to delay the resistance. The combination of neonicotinoids with pyrethroids was currently proposed but the mode of action of these compounds at synaptic and extrasynaptic levels needs to be further explored. In the present study, we evaluated the effect of the combination of two insecticides, permethrin and dinotefuran, on cockroach cholinergic synaptic transmission and on isolated cell bodies. We first found that combination of 5 μM permethrin and dinotefuran enhances depolarization of the sixth abdominal ganglion compared to dinotefuran alone, without an inhibition of the spontaneous activity. However, a pretreatment with 1 μM dinotefuran or permethrin before bath application of the mixture inhibits the ganglionic depolarization. Compared to permethrin, 1 μM dinotefuran induces a persistent enhancement of spontaneous activity. Interestingly, at extrasynaptic level, using dorsal unpaired median neurons and Kenyon cells, we found that combination of both 1 μM dinotefuran and permethrin resulted in an increase of the mixture-induced current amplitudes. Pretreatment with 1 μM dinotefuran strongly decreases the currents whereas permethrin induces a time-dependent inhibition. These data demonstrate that the combination of dinotefuran and permethrin enhances the effect of dinotefuran.

Evaluation of the anti-feeding and insecticidal effects of a topically administered combination of imidacloprid and permethrin (Advantix®) against Phlebotomus (Larroussius) perniciosus (Newstead, 1911) in dogs following monthly administration

BACKGROUND

Two laboratory experiments (Studies 1 and 2) were conducted to confirm the efficacy of an imidacloprid and permethrin combination (Advantix® Spot-on, Bayer) to repel and kill Phlebotomus (Larroussius) perniciosus sand flies when applied once a month topically to dogs.

METHODS

Both studies compared dogs treated with a combination containing 100 mg/ml imidacloprid + 500 mg/ml permethrin (Advantix® Spot-on, Bayer) to placebo treated dogs. The treatments were applied topically on Day -28 (Study 2) and Day 0 (Studies 1 and 2). Sand fly exposures with 80 unfed females were performed before the first treatment for allocation purposes and post-treatment on study days (SDs) 1, 7, 14, 21 and 28 (following first or second monthly treatment for Studies 1 and 2, respectively). After 60 min, sand flies were assessed for mortality and engorgement status.

RESULTS

Repellent evaluation (anti-feeding effect) on all days post-infestation showed efficacies that ranged between 88.1-99.3% during the first month and 92.2-98.9% during the second. Analyses of the comparison of fed sand fly counts for each treatment group resulted in a highly significant reduction (P < 0.0001) at all post-infestation time points for those dogs treated with Advantix®. A significant (P < 0.0001 for all time points) insecticidal effect was equally demonstrated. No treatment related adverse events were observed during the study.

CONCLUSIONS

In the present studies Advantix® Spot-on demonstrated to be safe and to provide excellent four-week sand fly (P. perniciosus) repellency of ≥88.1% and ≥92.2% after a first and second monthly treatment, respectively. A significant insecticidal effect was also observed.

Anti-feeding and insecticidal efficacy of a topical administration of dinotefuran-pyriproxyfen-permethrin spot-on (Vectra® 3D) on mice against Stegomyia albopicta (= Aedes albopictus)

An ectoparasiticide combining three active ingredients [dinotefuran, permethrin and pyriproxyfen (DPP)] was used in mice in an experiment designed to evaluate its anti-feeding and insecticidal efficacy against Stegomyia albopicta (= Aedes albopictus) (Diptera: Culicidae) mosquitoes. Twenty-two adult mice were randomly allocated into two groups consisting of an untreated control group and a DPP-treated group. Mice were exposed individually for 1 h to a mean ± standard deviation of 27 ± 2 starved female mosquitoes on days 1, 7, 14, 21 and 28 post-treatment. At the end of the exposure (1 h), mosquitoes were assessed for immediate survival and engorgement status. Additionally, live mosquitoes in both groups were incubated separately and observed for mortality at 24 h after the end of the exposure. The anti-feeding efficacy of DPP after the 1-h exposure period was 99.2, 100, 98.0, 89.3 and 87.4% at 1, 7, 14, 21 and 28 days, respectively. Levels of insecticidal efficacy evaluated at 1 h and 24 h after exposure on days 1, 7, 14, 21 and 28 were 36.7, 28.9, 30.8, 23.1 and 11.9%, and 68.4, 45.0, 43.3, 37.9 and 19.9%, respectively. Based on the mouse model, the present study demonstrates that the DPP combination has significant anti-feeding and insecticidal efficacy against S. albopicta for at least 4 weeks.

Novel Areas for Prevention and Control of Canine Leishmaniosis

There have been multiple recent advances regarding tools for the control and prevention of canine leishmaniosis (CanL), including new preventative vaccines. In this review, these advances are evaluated based on control targets, including vector and parasite. Leishvet recommendations are provided for control practices based on the dog's risk of infection. New topical insecticide formulations have proven to be effective in preventing sand fly bites, and subsequently infection. Parasite control occurs through chemotherapeutic or immunologic means, which decrease or prevent transmission to other animals, including humans. Leishmaniosis control programs that include a combination of coordinated measures, either in individuals or for prevention across reservoir populations, are required.

Field Evaluation of a New Strategy to Control Lutzomyia longipalpis, Based on Simultaneous Application of an Adulticide-Larvicide Mixture

Leishmania infantum (syn. chagasi) is the etiologic agent of visceral leishmaniasis in Argentina, and the phlebotomine fly Lutzomyia longipalpis is its main vector. The objective of this study was to evaluate the effectiveness of Dragon Max^®, an emulsifiable concentrate formulation containing the pyrethroid permethrin and the larvicide pyriproxyfen, for Lu. longipalpis control under field conditions. The work was conducted in the city of Posadas (Misiones province, Argentina). Comparisons were performed between treated and untreated peridomiciles with poultry, which met previously determined criteria for favoring the presence of Lu. longipalpis. Henhouses and their surrounding area were treated, with the formulation (100 mg of permethrin and 2 mg/m² of pyriproxyfen) applied using a hand pump sprayer. Untreated henhouses were used as controls. Phlebotomine abundance was monitored before treatment and then weekly, using Centers for Disease Control and Prevention light traps. Lutzomyia longipalpis was the only phlebotomine species captured. A male/female ratio of 2.5 was observed. The more chickens there were in the henhouses, the greater the number of phlebotomines captured. The treatment resulted in a significant decrease in the number of individuals, which persisted for at least 2 wk. This encouraging result provides a baseline for further studies evaluating the possibility of using Dragon Max as a tool for Lu. longipalpis control.

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

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

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

Owner adherence to the recommended treatment protocol;

Rapid onset of activity following administration;

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

Maintenance of high efficacy throughout the retreatment interval.

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

Current status on prevention and treatment of canine leishmaniasis

Canine leishmaniasis (CanL) is a parasite-borne disease mainly induced by Leishmania infantum in the Old World and Leishmania chagasi (infantum) in the New World. CanL is a zoonosis transmitted by the bite of infected Phlebotominae flies that act as vectors. CanL is a very serious disease that usually produces death when remains untreated and can be a focus of transmission to other dogs or humans. Infected dogs and other domestic and wild animals act as reservoirs and are a real threat to uninfected/healthy dogs and humans in endemic areas where the sand flies are present. Prevention of new infections in dogs can help to stop the current increase of the disease in humans, reinforcing the concept of "One Health" approach. The management of CanL is being performed using prophylactic measures in healthy dogs - insecticides impregnated in collars or immunostimulants applied by spot-on devices - and chemotherapy in animals that suffer from the disease. Antimonials as first-line monotherapy have proven efficacy in reducing most of the clinical signs of CanL, but they need to be administered during several days, and no complete parasite clearance is achieved, favouring the presence of relapses among treated dogs. Therefore, new drugs, such as miltefosine, or combinations of this drug or antimonials with allopurinol are in the pipeline of clinical treatment of CanL. Recently, there has been an emergence of protective - prophylactic - and curative - autogenous vaccines - immunotherapy tools to face CanL, whose results are still under study. This review highlights the current use of preventive and eradicative weapons to fight against this disease, which is a scourge for dogs and a continuous threat to human beings.

Effect of juvenoids pyriproxyfen and diofenolan on embryogenesis and postembryonic development of blow fly Chrysomya megacephala (Diptera: Calliphoridae) following egg treatment

The blow fly Chrysomya megacephala is a serious medico-veterinary pest causing myiasis in humans and animals apart from transmitting various disease-causing pathogens. Being an economically important pest, it warrants successful control in the early stages without affecting the host, environment, and non-target organisms. Juvenoids being safe, species and stage selective, biodegradable, and harmless to beneficial non-target organisms. Treatment of freshly laid eggs of C. megacephala with juvenoids pyriproxyfen and diofenolan (50 and 100 μg/cm(2)) by contact method for 1-60 min severely derailed the embryogenesis and postembryonic development. The results included the following: reduced eclosion, dead, non-viable eggs, undeveloped embryos of various stages, and fully developed embryos entrapped in chorion and unable to eclose. Several latent effects of juvenoids were also observed like larval mortality in the first instar, abnormal pupariation, reduced normal pupariation, formation of pupal-adult mosaics, suppression of adult emergence, and emergence of only deformed adults. Diofenolan was found to be more potent than pyriproxyfen in suppressing embryogenesis. These results show that the juvenoids pyriproxyfen and diofenolan have the potential to be judiciously used along with other bio-rational methods for the successful control of C. megacephala.

Repellent and insecticidal efficacy of a new combination of fipronil and permethrin against the main vector of canine leishmaniosis in Europe (Phlebotomus perniciosus)

BACKGROUND

Two successive laboratory experiments (A and B) were conducted to confirm the efficacy of a new fipronil and permethrin combination to repel and kill Phlebotomus perniciosus sandflies when applied once topically on dogs.

METHODS

Due to the difficulty to get enough available dogs and sandflies in one run, the study was divided into 2 experiments which had exactly the same design, and were conducted at the same place, with the same technicians. They compared dogs treated with a combination containing 67.6 mg/mL fipronil + 504.8 mg/mL permethrin (Frontect/Frontline Tri-Act, Merial) to untreated dogs. The treatments were applied topically once on Day 0. Sandfly exposures were performed on Days 1, 7, 14, 21 and 29 with 80 P. perniciosus female sandflies. After 60 min, sandflies were assessed for vitality and engorgement status. Live sandflies were kept in an insectary and observed for mortality counts 4 h after the exposure period ended.

RESULTS

Percent sandfly repellency on treated dogs was 98.2, 98.5, 99.2, 90.9 and 90.3%, for Days 1, 7, 14, 21, and 29, respectively. There was a significant difference (p ≤ 0.05) between the treated and control groups in both experiments and for the pooled data on every assessment day. Insecticidal efficacy on treated dogs at 4 h post-exposure on Days 1, 7, 14, 21 and 29 was 98.7, 99.7, 96.8, 93.4, and 78.9%, respectively. There was a significant difference between the treated and control groups for live sandflies observed at 4 h post-exposure for all assessment days (p < 0.05).

CONCLUSIONS

A single topical administration of a new combination of fipronil and permethrin demonstrated a significant repellent effect (i.e., > 80%) against P. perniciosus which lasted for 29 days after application. The repellent effect was accompanied by a significant insecticidal effect on sandflies. The results suggest that in endemic areas, the application of the fipronil-permethrin combination could be integrated into canine leishmaniosis prevention program.

Anti-feeding efficacy of Activyl® Tick Plus topical treatment of dogs against Phlebotomus perniciosus

BACKGROUND

Topical permethrin treatment is known to prevent feeding of sandflies on dogs. This study investigated the anti-feeding efficacy and the immediate insecticidal efficacy (knock-down effect) of topical treatment of dogs with a new commercially available combination of indoxacarb and permethrin (Activyl® Tick Plus), compared with a negative control.

METHODS

Sedated dogs were individually exposed to unfed female sandflies in a darkened chamber for one hour 2, 7, 14, 21 and 29 days after treatment. Mean fly feeding and survival rates in the two groups after one hour of exposure were used to calculate the anti-feeding efficacy and the knock-down effect, respectively.

RESULTS

On Days 2, 7, 14, 21 and 29 post treatment, the anti-feeding efficacy was 99, 98, 96, 88 and 84% based on geometric means. The mean number of fed sandflies in the treated group was significantly lower than in the control group mean at every evaluation time point. The knock-down effect, measured at one hour after exposure of the flies to treated dogs, was 32, 27, 9, 0 and 4% based on geometric means, at the same time points. The number of dead flies was significantly higher in the treated group on Days 2 and 7 post-treatment. No adverse effects of treatment were observed at any time during the study.

CONCLUSIONS

Activyl® Tick Plus treatment of dogs provided a high anti-feeding efficacy against Phlebotomus perniciosus from 2 to 21 days post treatment, with continuing significant anti-feeding to 29 days post-treatment, and was well tolerated. Some knock-down effect following one hour of exposure of flies to treated dogs was observed in the first week after treatment.

Role of wildlife in the epidemiology of Leishmania infantum infection in Europe

Although dogs are considered the main reservoir of Leishmania infantum infection in endemic areas in Europe, the existence of other wild vertebrate reservoirs has been proposed as a possible cause of the lack of success of control measures. Evidence of L. infantum infection in European wildlife has been reported in carnivores, lagomorphs, and rodents. The red fox (Vulpes vulpes) received most attention, probably due to its taxonomic relationship with the dog and because it is the most abundant wild carnivore in Europe. Foxes and other wild carnivores often displayed high prevalences of infection but their infectiveness to the sandfly vector has never been demonstrated. However, xenodiagnosis demonstrated that black rats (Rattus rattus), are infectious to sandflies. This, together with their relative abundance, high rates of infection, and the fact that infected rats have been found on a Mediterranean island where dogs are not present, makes rats good candidate to be reservoirs of L. infantum. Recently, the Iberian hare (Lepus granatensis) has been recognized as the origin of a leishmaniosis outbreak in humans in Spain and xenodiagnosis showed that this species is also able to infect sandflies. In contrast, a recent survey in cave bats failed to detect infected individuals. In the future, the comparison of parasite isolates from humans, dogs and wildlife, xenodiagnosis studies in wild carnivores, and the study of other vertebrate taxonomic groups will help determine the current role of European wildlife in the epidemiology of leishmaniosis.