Efficacy of selamectin, spinosad, and spinosad/milbemycin oxime against the KS1 Ctenocephalides felis flea strain infesting dogs

Ovicidal action of insectoacaricide drugs sentry home, Neostomazan 1:200 manufacured by CEVA, Neostomazan 1:200 manufacured by product and Extrazol M on fleas Ctenocephalides spp. eggs

The aim of the research. To compare the ovicidal efficiency of insectoacaricides of different composition and manufacturers on flea eggs (Ctenocephalides spp.) for treatemnt of the premises where animals live. Materials and methods of the research. The study was conducted on the basis of the clinic of veterinary medicine "Vetservice" Sumy, laboratory "Veterinary Pharmacy" and "Innovative technologies and safety and quality of livestock products" of Sumy National Agrarian University. The ovicidal effect of insectoacaricides on flea eggs of Ctenocephalides spp. was studied. Ctenocephalides spp. eggs were selected from the pet bedding on which the animal spended most of its time, namely the cats. The studied material was selected with a cosmetic brush. Ctenocephalides spp. eggs were placed into a Petri dish of 10 eggs per each dish. The test material was introduced with a dental probe. There were 4 test dishes, which were treated with insectoacaricides (each test dish was treated with a separate drug) and 1 control dish with no treatment. Microscopy was conducted under a light microscope with magnification X8 of each egg, with following treatment of each egg with insectoacaricides. Monitoring was conducted in 24, 48 and 72 hours after treatment. Results. Research has shown that drugs which demonstrated 100 % ovicidal effectiveness were Sentry Home (pyriproxyfen – 0.02 %, permethrin – 0.2 %, n-Octyl Bicyclohepten – 1.0 %) in 24 hours and Neostomazan (CEVA)(transmix – 5.0 g, tetramethrin – 0.5 g) in 72 hours. Conclusions. Insectoacaricide drug Sentry Home (pyriproxyfen – 0.02 %, permethrin – 0.2 %, n-Octyl Bicyclohepten – 1.0 %), used for the treatment of the premises where the animals live, showed the most pronounced ovicidal effect in 24 hours.

Complementary effect of mechanism of multidrug resistance in Trichophyton mentagrophytes isolated from human dermatophytoses of animal origin

BACKGROUND

Dermatophytoses have gained interest worldwide due to the increased resistance to terbinafine and azoles and difficulty in management of these refractory diseases.

OBJECTIVES

In this study, we identified and analysed Trichophyton mentagrophytes clinical isolates obtained from humans with infections of animal origin.

METHODS

We used quantitative real-time PCR (qRT-PCR) to examine the transcriptional modulation of three MDR genes (PDR1, MDR2 and MDR4) and analysed squalene epoxidase (SQLE) gene sequences from multidrug-resistant Trichophyton mentagrophytes isolates.

RESULTS

The expression profile revealed a 2- to 12-fold increase in mRNA accumulation in the presence of any of the antifungals, compared to cells incubated without drugs. A statistically significant relationship between the isolates exposed to itraconazole and increased expression of the tested genes was revealed. Substantially lower transcription levels were noted for cells exposed to luliconazole, that is, a third-generation azole. Additionally, in the case of 50% of terbinafine-resistant strains, Leu397Phe substitution in the SQLE gene was detected. Furthermore, the reduced susceptibility to itraconazole and voriconazole was overcome by milbemycin oxime.

CONCLUSIONS

In conclusion, our study shed more light on the role of the ABC transporter family in T. mentagrophytes, which, if overexpressed, can confer resistance to single azole drugs and even cross-resistance. Finally, milbemycin oxime could be an interesting compound supporting treatment with azole drugs in the case of refractory dermatomycoses.

Highly Conserved Homotrimer Cavity Formed by the SARS-CoV-2 Spike Glycoprotein: A Novel Binding Site

An important stage in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) life cycle is the binding of the spike (S) protein to the angiotensin converting enzyme-2 (ACE2) host cell receptor. Therefore, to explore conserved features in spike protein dynamics and to identify potentially novel regions for drugging, we measured spike protein variability derived from 791 viral genomes and studied its properties by molecular dynamics (MD) simulation. The findings indicated that S2 subunit (heptad-repeat 1 (HR1), central helix (CH), and connector domain (CD) domains) showed low variability, low fluctuations in MD, and displayed a trimer cavity. By contrast, the receptor binding domain (RBD) domain, which is typically targeted in drug discovery programs, exhibits more sequence variability and flexibility. Interpretations from MD simulations suggest that the monomer form of spike protein is in constant motion showing transitions between an "up" and "down" state. In addition, the trimer cavity may function as a "bouncing spring" that may facilitate the homotrimer spike protein interactions with the ACE2 receptor. The feasibility of the trimer cavity as a potential drug target was examined by structure based virtual screening. Several hits were identified that have already been validated or suggested to inhibit the SARS-CoV-2 virus in published cell models. In particular, the data suggest an action mechanism for molecules including Chitosan and macrolides such as the mTOR (mammalian target of Rapamycin) pathway inhibitor Rapamycin. These findings identify a novel small molecule binding-site formed by the spike protein oligomer, that might assist in future drug discovery programs aimed at targeting the coronavirus (CoV) family of viruses.

Larvicidal activity of spinosad and its impact on oviposition preferences of the West Nile vector Culex pipiens biotype molestus - A comparison with a chitin synthesis inhibitor

In the present study, the larvicidal activity of ageing aqueous suspensions of spinosad against larvae of Culex pipiens biotype molestus, as well as their effect on the oviposition preferences of adult gravid females were evaluated in laboratory bioassays. Spinosad was applied at its label dose and the aqueous stock suspensions were stored for various ageing intervals up to 38 days. Untreated distilled water and diflubenzuron served as negative and positive control, respectively. Stock suspensions were taken after 0, 2, 6, 8, 16, 30 and 38 days of storage for diflubenzuron and after 0, 2, 6, 8, 20 and 27 days for spinosad, and were used for the bioassays. Furthermore, the effect of spinosad on the oviposition response of Cx. p. biotype molestus gravid females was investigated in two-choice oviposition preference bioassays. Spinosad was evaluated at half of its label dose and at its label dose, whereas diflubenzuron and distilled water served as positive and negative control, respectively. Results showed that both insecticides were found highly effective for the control of Cx. p. biotype molestus larvae, for ageing intervals up to 27 and 38 days for spinosad and diflubenzuron, respectively. Spinosad acted immediately after the preparation of the insecticidal solution (LT₅₀ = 1.5 h), whereas for aged samples, LT₅₀ values increased with the increase of the ageing interval (LT₅₀ = 5 days for the 27 days old sample). For diflubenzuron, ageing time increased its insecticidal activity, as for aged diflubenzuron-treated solutions, lower LT₅₀ values were achieved. In the oviposition preference bioassays, significantly fewer egg rafts were laid in water treated with spinosad at its label dose compared to control. However, this was not the case for water treated with spinosad at half of its label dose. Oviposition Activity Index (OAI) values were always comprised between -0.3 and 0.3, showing no relevant oviposition deterrence or attraction. The results of the present study contribute to our understanding of the effect of ageing on insecticidal solutions widely used in urban areas to control Cx. p. biotype molestus. Although an important vector of high public health importance, Cx. p. biotype molestus has been scarcely studied as target of environmentally and toxicologically reduced risk insecticides, such as spinosad.

Suspected adverse drug interaction between spinosad and milbemycin oxime in a cat

CASE SUMMARY

A 12-year-old male neutered Tonkinese cat was presented for acute ataxia, weakness, altered mentation and generalised tremors. The cat had been administered oral spinosad (140 mg; 33.5 mg/kg) 48 h prior to the onset of clinical signs, and an oral anthelmintic containing milbemycin oxime (16 mg; 3.8 mg/kg) and praziquantel (40 mg; 9.6 mg/kg) 12 h before the onset of clinical signs. On physical examination, dull-to-obtunded mentation, tetraparesis, ataxia and mild tremors of facial, limb and trunk muscles were noted. Serum biochemical changes and urinalysis were consistent with haemoconcentration. The results of a complete blood count, urine culture and serology for feline leukaemia virus, feline immunodeficiency virus and cryptococcal antigen were negative. The patient was monitored in hospital and all clinical signs resolved within 24 h.

RELEVANCE AND NOVEL INFORMATION

The neurological signs in this case were consistent with macrocyclic lactone neurotoxicity, which is suspected to have occurred from an adverse drug interaction between spinosad and milbemycin oxime. This report serves to highlight the potential for this adverse drug interaction between these commonly used prophylactic drugs.

The Biology and Ecology of Cat Fleas and Advancements in Their Pest Management: A Review

The cat flea Ctenocephalides felis felis (Bouché) is the most important ectoparasite of domestic cats and dogs worldwide. It has been two decades since the last comprehensive review concerning the biology and ecology of C. f. felis and its management. Since then there have been major advances in our understanding of the diseases associated with C. f. felis and their implications for humans and their pets. Two rickettsial diseases, flea-borne spotted fever and murine typhus, have been identified in domestic animal populations and cat fleas. Cat fleas are the primary vector of Bartonella henselae (cat scratch fever) with the spread of the bacteria when flea feces are scratched in to bites or wounds. Flea allergic dermatitis (FAD) common in dogs and cats has been successfully treated and tapeworm infestations prevented with a number of new products being used to control fleas. There has been a continuous development of new products with novel chemistries that have focused on increased convenience and the control of fleas and other arthropod ectoparasites. The possibility of feral animals serving as potential reservoirs for flea infestations has taken on additional importance because of the lack of effective environmental controls in recent years. Physiological insecticide resistance in C. f. felis continues to be of concern, especially because pyrethroid resistance now appears to be more widespread. In spite of their broad use since 1994, there is little evidence that resistance has developed to many of the on-animal or oral treatments such as fipronil, imidacloprid or lufenuron. Reports of the perceived lack of performance of some of the new on-animal therapies have been attributed to compliance issues and their misuse. Consequentially, there is a continuing need for consumer awareness of products registered for cats and dogs and their safety.

Systemic insecticide treatment of the canine reservoir of Trypanosoma cruzi induces high levels of lethality in Triatoma infestans, a principal vector of Chagas disease

BACKGROUND

Despite large-scale reductions in Chagas disease prevalence across Central and South America, Trypanosoma cruzi infection remains a considerable public health problem in the Gran Chaco region where vector-borne transmission persists. In these communities, peridomestic animals are major blood-meal sources for triatomines, and household presence of infected dogs increases T. cruzi transmission risk for humans. To address the pressing need for field-friendly, complementary methods to reduce triatomine infestation and interrupt T. cruzi transmission, this study evaluated the systemic activity of three commercial, oral, single dose insecticides Fluralaner (Bravecto®), Afoxolaner (NexGard®) and Spinosad (Comfortis®) in canine feed-through assays against Triatoma infestans, the principal domestic vector species in the Southern Cone of South America.

METHODS

Twelve healthy, outbred dogs were recruited from the Zoonosis Surveillance and Control Program in Santa Cruz, Bolivia, and randomized to three treatment groups, each containing one control and three treated dogs. Following oral drug administration, colony-reared second and third stage T. infestans instars were offered to feed on dogs for 30 min at 2, 7, 21, 34 and 51 days post-treatment.

RESULTS

Eighty-five per cent (768/907) of T. infestans successfully blood-fed during bioassays, with significantly higher proportions of bugs becoming fully-engorged when exposed to Bravecto® treated dogs (P < 0.001) for reasons unknown. Exposure to Bravecto® or NexGard® induced 100% triatomine mortality in fully- or semi-engorged bugs within 5 days of feeding for the entire follow-up period. The lethality effect for Comfortis® was much lower (50-70%) and declined almost entirely after 51 days. Instead Comfortis® treatment resulted in substantial morbidity; of these, 30% fully recovered whereas 53% remained morbid after 120 h, the latter subsequently unable to feed 30 days later.

CONCLUSIONS

A single oral dose of Fluralaner or Afoxolaner was safe and well tolerated, producing complete triatomine mortality on treated dogs over 7.3 weeks. While both drugs were highly efficacious, more bugs exposed to Fluralaner took complete blood-meals, and experienced rapid knock-down. Coupled with its longer residual activity, Fluralaner represents an ideal insecticide for development into a complementary, operationally-feasible, community-level method of reducing triatomine infestation and potentially controlling T. cruzi transmission, in the Gran Chaco region.

Systemic insecticides used in dogs: potential candidates for phlebotomine vector control?

Zoonotic visceral leishmaniasis (ZVL) is a public health problem endemic in some countries. Current control measures, in particular culling infected dogs, have not reduced ZVL incidence in humans. We evaluated the use of five systemic insecticides (spinosad, fluralaner, afoxolaner, sarolaner and moxidectin) currently used in dogs for other purposes (e.g. tick, flea control) in controlling ZVL transmission. The anti-phlebotomine capacity of these compounds confirmed in experimental studies makes their use in ZVL control programmes very promising. Limitations and benefits of using this new control tool are compared to current practices.

Characterization of Haemonchus contortus P-glycoprotein-16 and its interaction with the macrocyclic lactone anthelmintics

Anthelmintic resistance in veterinary nematodes, including Haemonchus contortus, has become a limitation to maintaining high standards of animal health. Resistance in this parasite, to all drug families including the macrocyclic lactones (MLs) is a serious issue worldwide. Mechanisms of resistance to the MLs appear to be complex and to include the elimination of these compounds by ABC transporter-like proteins present in nematodes. In order to investigate the potential involvement of ABC transporters in ML resistance in H. contortus, we have characterized the functionality of the ABC transporter H. contortus P-glycoprotein-16 (Hco-PGP-16) expressed in mammalian cells. This has included a study of its interaction with different MLs, including the avermectins, abamectin (ABA) and ivermectin (IVM), and the milbemycin, moxidectin (MOX). Hco-PGP-16 transport activity was studied using the fluorophore Rhodamine 123 (Rho 123). Transfected cells expressing Hco-PGP-16 accumulated less than 50% of Rho 123 than control cells, suggesting an active transport of this tracer dye by Hco-PGP-16. The influence of the MLs on the Rho123 transport by Hco-PGP-16 was then investigated. A marked inhibition of Rho123 transport by ABA and IVM was observed. In contrast, MOX showed less effect on inhibition of Rho123 transport by Hco-PGP-16, and the inhibition was not saturable. The difference in the interaction of the avermectins and MOX with Hco-PGP-16 may help explain the slower rate of development of resistance to MOX compared with the avermectins in H. contortus.

Speed of flea knockdown of spinosad compared to afoxolaner, and of spinosad through 28 days post-treatment in controlled laboratory studies

BACKGROUND

The speed of flea knockdown by different products and their duration of effectiveness are factors which affect veterinarian prescribing decisions. To further validate the month-long pulicidal effectiveness of spinosad and determine its rate of flea knockdown to that of afoxolaner, three studies were conducted in two laboratories in the United States, utilizing flea infestations from colonies which are regularly refreshed through introduction of locally caught fleas.

METHODS

All study assessors were blinded, dogs were ranked by pre-study flea counts and randomized accordingly, and treatments administered on Day 0. All studies included a negative control group; two also included an afoxolaner group. In one study, flea challenges for treated and control dogs (10 per group) were completed 21 and 28 days after treatment and counts were performed 24 h later. In each of two speed-of-knockdown (SOK) studies, 36 dogs were randomized, six dogs per group, to: untreated controls; administered oral afoxolaner (2.6-6.2 mg/kg); or oral spinosad (32.1-59.2 mg/kg). In the SOK studies, live fleas from Day -1 infestations were counted after being combed off at 1 and 3 h after treatment, and after reinfestations on Day 7.

RESULTS

There were no treatment-related adverse events. Spinosad was 98.6% effective at 28 days post treatment. For SOK, geometric mean live flea counts for afoxolaner were not different from controls at any assessment. For spinosad, all mean counts were significantly lower than in controls (p ≤ 0.0128) except at 1 h post treatment in both studies. Spinosad was significantly more effective than afoxolaner in both studies at 3 h post treatment (p ≤ 0.0065) and post-Day 7 infestation (p ≤ 0.0054), and at 1 h post treatment (p = 0.0276) and post-Day 7 infestation in one study.

CONCLUSIONS

These data validate spinosad's faster onset of flea knockdown than afoxolaner against infestations present at the time of treatment, and faster residual speed of flea knockdown for at least 7 days post treatment, and confirm spinosad's extended residual speed of kill for at least 28 days post treatment.

Canine atopic dermatitis: detailed guidelines for diagnosis and allergen identification

BACKGROUND

Canine atopic dermatitis (AD) is a common, genetically predisposed, inflammatory and pruritic skin disease. The variation in clinical presentations, due to genetic factors, extent of the lesions, stage of the disease, secondary infections, as well as resemblance to other non-atopic related skin diseases, can complicate a diagnosis of canine AD. A sub-group of the International Committee for Allergic Diseases in Animals (ICADA) was tasked with the development of a set of practical guidelines that can be used to assist practitioners and researchers in the diagnosis of canine AD. Online citation databases and abstracts from international meetings were searched for publications related to the topic, and combined with expert opinion where necessary. The final set of guidelines was approved by the entire ICADA committee.

RESULTS

A total of 81 publications relevant for this review were identified. The guidelines generated focus on three aspects of the diagnostic approach: 1. Ruling out of other skin conditions with clinical signs resembling, or overlapping with canine AD. 2. Detailed interpretation of the historical and clinical features of patients affected by canine AD. 3. Allergy testing by intradermal versus allergen-specific IgE serum testing.

CONCLUSIONS

The diagnosis of canine AD is based on meeting clinical criteria and ruling out other possible causes with similar clinical signs. Flea combing, skin scraping and cytology should be performed, where necessary, as part of a thorough work-up. Elimination diet trials are required for patients with perennial pruritus and/or concurrent gastrointestinal signs. Once a clinical diagnosis of canine AD is made, allergy testing can be performed to identify potential causative allergens for allergen-specific immunotherapy.

A field trial of spinosad for the treatment and prevention of flea infestation in shepherd dogs living in close proximity to flea-infested sheep

Background

Three flea species, Pulex irritans, Ctenocephalides canis and C. felis parasitize shepherd dogs living on sheep farms in Greece. The aim of this randomized, blinded, placebo-controlled trial was to examine the efficacy of spinosad, when administered three times every 4 weeks, as the only intervention to treat and prevent flea infestations in shepherd dogs living on sheep farms.

Methods

Thirty dogs living on sheep farms and infested by at least 24 fleas were randomly allocated into equal groups. Group A dogs received spinosad (45–70 mg/kg body weight), every 4 weeks for three administrations, whereas Group B dogs were placebo-treated. Flea counting was performed at the beginning of the trial (day 0) and after 14, 28, 56 and 84 days. The first five fleas from each dog and 2–6 fleas collected from 5–11 sheep were used for species identification.

Results

The percentage of dogs with zero flea counts was significantly higher in group A than in group B at days 14, 28, 56 and 84 and flea counts were significantly lower in group A than in group B at days 14, 28, 56 and 84. In group A, flea counts were significantly lower at days 14, 28, 56 and 84 compared to day 0 whereas there were no changes in flea counts of group B dogs. The percent efficacy of spinosad for the treatment and prevention of flea infestation was higher than 98 % (arithmetic means) or higher than 99 % (geometric means) throughout the study. No adverse reactions were recorded.

C. canis was the predominant flea species of dogs at day 0. In group A the relative abundance of C. felis increased at day14 whereas in group B the relative abundance of P. irritans increased at days 14, 28, 56 and 84.

Conclusions

Spinosad is safe and effective for the treatment of C. canis and C. felis infestations and for the prevention of P. irritans, C. canis and C. felis infestations in shepherd dogs living in close proximity to sheep.