Insecticide/acaricide resistance in fleas and ticks infesting dogs and cats

Epidemiology of sarcoptic mange in free-ranging vicuñas (Vicugna vicugna): a cross-sectional study in Andean highland communities in Peru

Sarcoptic mange or scabies is a contagious parasitic skin disease that affects a wide range of domestic and wildlife species. A cross-sectional study was carried out to determine the prevalence, molecular identification, and characteristics of sarcoptic mange in vicuñas. A total of 3,274 vicuñas were examined. Following ritual harvesting events ("chaccus") in 13 Andean communities. The presence of mange mites was determined by the skin scraping technique and confirmed by PCR analysis using specific primers for the ITS2 gene of Sarcoptes scabiei. The presence of mange mites was also confirmed by microscopy using samples taken from wallows. A data collection form was used to register the characteristics of the vicuñas sampled. The prevalence of sarcoptic mange was 4.9% (95% CI: 4.1 - 5.6%). All samples from wallows tested positive (9/9). Importantly, the presence of the species S. scabiei was molecularly confirmed. Adult females with regular body condition were more susceptible to sarcoptic mange, although the lesions were mild. This study confirms the presence of S. scabiei in semi-captive vicuñas and points to the possible role of wallows in the dissemination of Sarcoptes mites.

Genetic Diversity of Rhipicephalus (Boophilus) microplus for a Global Scenario: A Comprehensive Review

Rhipicephalus microplus poses a substantial threat to livestock health and agricultural economies worldwide. Its remarkable adaptability to diverse environments and hosts is a testament to its extensive genetic diversity. This review delves into the genetic diversity of R. microplus, employing three pivotal genetic markers: the cytochrome c oxidase I (COX1) gene, ribosomal genes, and microsatellites. The COX1 gene, a crucial tool for genetic characterization and phylogenetic clustering, provides insights into the adaptability of ticks. Ribosomal genes, such as internal transcribed spacer regions (ITS-1 and2) as well as 18S and 28S, are routinely utilized for species differentiation. However, their use is limited due to indels (insertions and deletions). Microsatellites and minisatellites, known for their high polymorphism, have been successfully employed to study populations and genetic diversity across various tick species. Despite their effectiveness, challenges such as null alleles and marker variations warrant careful consideration. Bm86, a well-studied vaccine candidate, exhibits substantial genetic diversity. This diversity directly influences vaccine efficacy, posing challenges for developing a universally effective Bm86-based vaccine. Moreover, the review emphasizes the prevalence of genes associated with synthetic pyrethroid resistance. Identifying single nucleotide polymorphisms in the acaricide-resistant genes of R. microplus has facilitated the development of molecular markers for detecting and monitoring resistance against synthetic pyrethroids. However, mutations in sodium channels, the target site for synthetic pyrethroid, correlate well with the resistance status of R. microplus, which is not the case with other acaricide target genes. This study underscores the importance of understanding genetic diversity in developing effective tick management strategies. The choice of genetic marker should be tailored based on the level of taxonomic resolution and the group of ticks under investigation. A holistic approach combining multiple markers and integrating additional molecular and morphological data may offer a more comprehensive understanding of tick diversity and relationships. This research has far-reaching implications in formulating breeding programs and the development of vaccine against ticks and tick-borne diseases (TTBDs) as well as strategies for the management of resistant ticks.

Nanoemulsion-based plant essential oil formulations: in vitro evaluation of pesticidal activity against ectoparasites in poultry

Ectoparasite infestations significantly impact the health and productivity of poultry. Chemical applications, although common for pest control, lead to pesticide residues and parasite resistance in poultry. Nanoemulsion-based plant essential oil formulations (NEOFs) provide a promising alternative for controlling poultry ectoparasites. This study aimed to assess the efficacy of NEOFs from clove, cinnamon, and turmeric essential oils (EOs) against ectoparasites, Menopon gallinae and Megninia ginglymura, under laboratory conditions. The toxicity and repellent properties of the NEOFs were examined, with the major chemical compounds of the EOs analyzed using chromatography mass spectrometer. Results identified eugenol as the dominant component in clove and cinnamon EOs (84.60 and 75.19%, respectively), while turmerone (68.46%) was the major compound in turmeric EO. NEOFs with clove:cinnamon:turmeric ratios of 4:0:0, 2:2:0, and 2:0:2 had particle size of 20.76 nm, 20.66 nm, and 89.56 nm, respectively, while those based on eugenol and turmerone standards had sizes <21.0 nm. In addition, NEOFs at 0.3% concentration with ratios of 4:0:0 and 2:2:0 achieved full control of both ectoparasites. These formulas demonstrated exceptional potency in exterminating ectoparasites, with LC50 and LC90 at <0.160 and <0.250%, respectively, 6 h after treatments. Furthermore, both NEOFs showed higher repellence responses in M. gallinae compared to M. ginglymura. The toxicities of these NEOFs were comparably effective against both parasites, showing no significant difference compared with chemical insecticide treatment. Therefore, further research will explore the practicality of using clove and cinnamon-derived NEOFs under farm conditions.

In vitro evaluation of the activity of Cinnamaldehyde as an inhibitor of the biological cycle of Ctenocephalides felis felis

The objective of this work was to evaluate the in vitro activity of cinnamaldehyde as an inhibitor of the biological cycle of Ctenocephalides felis felis. Tests were carried out with six repetitions containing 10 eggs of C. felis felis together with 0.5g of diet and filter paper discs with area of 23.76 cm2 impregnated with different concentrations of cinnamaldehyde (6; 8; 10; 12; 14; 16; 18; 20; 24 and 28 µg.cm-2) in Petri dishes and incubated in a climate-controlled chamber at 27 ± 1 °C and RH 75 ± 10%, for 30 days. The tests included a placebo group containing the diluent (acetone) and a negative control group, without treatment. At the end of 30 days, the percentage of inhibition of adult emergence/mortality was calculated, as well as the LC50 and LC90. Inhibition of adult emergence greater than 50% was observed from a concentration of 10 µg.cm-2 and 100% inhibition from a concentration of 14 µg.cm-2, obtaining LC50 and LC90 results of 8.75 and 13.57 µg.cm-2, respectively. We concluded that the volatile compound cinnamaldehyde is effective in vitro as an inhibitor of the biological cycle of C. felis felis.

Microbiota in disease-transmitting vectors

Haematophagous arthropods, including mosquitoes, ticks, flies, triatomine bugs and lice (here referred to as vectors), are involved in the transmission of various pathogens to mammals on whom they blood feed. The diseases caused by these pathogens, collectively known as vector-borne diseases (VBDs), threaten the health of humans and animals. Although the vector arthropods differ in life histories, feeding behaviour as well as reproductive strategies, they all harbour symbiotic microorganisms, known as microbiota, on which they depend for completing essential aspects of their biology, such as development and reproduction. In this Review, we summarize the shared and unique key features of the symbiotic associations that have been characterized in the major vector taxa. We discuss the crosstalks between microbiota and their arthropod hosts that influence vector metabolism and immune responses relevant for pathogen transmission success, known as vector competence. Finally, we highlight how current knowledge on symbiotic associations is being explored to develop non-chemical-based alternative control methods that aim to reduce vector populations, or reduce vector competence. We conclude by highlighting the remaining knowledge gaps that stand to advance basic and translational aspects of vector-microbiota interactions.

Monitoring the development of Ctenocephalides felis felis (Siphonaptera, Pulicidae) eggs from a laboratory colony in Brazil subjected to different adhesive substances

This study aimed to evaluate the use of different adhesive substances in an method to monitor the development of C. felis felis eggs. Three adhesive substances were selected: cyanoacrylate, stick glue, and liquid silicone. The eggs were obtained from a laboratory colony and placed on a thin layer of adhesive substance on the lid of a Petri dish to prevent contact with the larval growth substrate. One hundred eggs were used for each adhesive substance. The development of the eggs was monitored for three consecutive days, during which larval hatching and egg characteristics were observed. Of the 100 eggs incubated for each adhesive substance, 64, 51, and 76 larvae hatched and survived from the stick glue, cyanoacrylate, and liquid silicone plates, respectively. After 30 days of incubation, 59, 45, and 68 hatched adults were observed, respectively, in these groups. The mean hatching of larvae and adults between the liquid silicone and cyanoacrylate groups differed statistically (p < 0.05). This study demonstrated positive results, and that liquid silicone was the most easily applicable adhesive substance on the plate and interfered less with egg development, therefore having the best larval recovery compared to incubated eggs compared to the other substances.

Determination of a Discriminant Dose to Identify Resistance to Amitraz in Rhipicephalus sanguineus s.l. (Acari: Ixodidae) from Mexico

The brown dog tick, Rhipicephalus sanguineus s.l., is considered the most widely distributed three-host tick in the world and has medical and veterinary importance; the control of infestation is carried out with acaricides, towards which it can develop resistance. This study aimed to determine the discriminant dose (d.d) of amitraz to identify resistance in R. sanguineus s.l. larvae natives from Mexico and to evaluate its application in field-collected ticks. Engorged ticks were collected from naturally infested dogs residing in rural communities and were incubated for 25 days, and their progeny was used in a larval immersion test (LIT) to be exposed to the d.d. determined in Rhipicephalus microplus, and those that were susceptible were analyzed using the LIT in six concentrations. Mortality was analyzed through probit methodology to calculate the lethal concentration (LC) 50 and 99. The d.d. was determined as a consensus value by multiplying the LC99 × 2, and then, we proceeded to evaluate it in in-field samples by using the LIT technique. The d.d. calculated was 4 ppm. The in-field evaluation found 64% of the resistant samples to amitraz with mortality percentages between 98.3% and 0.35%. This dose can be used to rapidly and inexpensively identify resistant populations in samples collected in the field.

Bartonella spp. in households with cats: Risk factors for infection in cats and human exposure

The aim of this study was to estimate the occurrence of Bartonella spp. per household in cats and the risk factors for Bartonella spp. positivity in cats and their owners from Valdivia, Chile. A total of 464 cats (distributed within 324 households) and 326 humans (control group [n = 112] and cat owner [n = 214]) distributed in 262 households were sampled. From the cat owners (n = 214), 128 humans were in households where the cat was also sampled, totaling 84 households with dual sampling. Real-time PCR (qPCR) was used for Bartonella spp. detection in blood from cats and humans, and immunofluorescent immunoassay (IFA) anti-Bartonella henselae was performed in human serum samples. Out of the total of 324 households, 20.43% presented at least one Bartonella positive cat. From the households with dual sampling, 29.7% (25/84) presented at least one qPCR-Bartonella spp. positive cat. However, Bartonella DNA was not amplified in humans, and in 7.3% (6/82) of the households was found at least one of the cat's owners exposed to B. henselae. Cats younger than one year (Odds Ratio (OR) = 5.3), non-neutered (OR 3.46), sampled at home (OR 5.82), and with improper application of tick/flea control products (OR 3.13) showed a higher risk for Bartonella spp. presence. Humans with occupational exposure involving animal contact, were more likely to exhibit B. henselae seropositivity (OR 7.5). Bartonella spp. was present in the cats a moderate number of households, but Bartonella DNA was not detected in owners' blood, inferring that there is a low risk of recent human infection in the studied population.

Management of the poultry red mite Dermanyssus gallinae with physical control methods by inorganic material and future perspectives

Poultry red mite (PRM), the ectoparasitic mite Dermanyssus gallinae found in laying hen farms, is a significant threat to poultry production and human health worldwide. It is a suspected disease vector and attacks hosts' other than chickens, including humans, and its economic importance has increased greatly. Different strategies to control PRM have been widely tested and investigated. In principle, several synthetic pesticides have been applied to control PRM. However, recent alternative control methods to avoid the side effects of pesticides have been introduced, although many remain in the early stage of commercialization. In particular, advances in material science have made various materials more affordable as alternatives for controlling PRM through physical interactions between PRM. This review provides a summary of PRM infestation, and then includes a discussion and comparison of different conventional approaches: 1) organic substances, 2) biological approaches, and 3) physical inorganic material treatment. The advantages of inorganic materials are discussed in detail, including the classification of materials, as well as the physical mechanism-induced effect on PRM. In this review, we also consider the perspective of using several synthetic inorganic materials to suggest novel strategies for improved monitoring and better information regarding treatment interventions.

Joint toxicity of insecticides against Hyalomma asiaticum

Hyalomma asiaticum, a hematophagous ectoparasite, causes severe economic losses. We studied the acute toxicity of five pesticides (three single-agent and two combination preparations) to this organism. Engorged larval ticks were immersed in ten serial concentrations of each insecticide and observed for 20 days. The LC₅₀ values of the five insecticides and the cotoxicity coefficients (CTCs) of the two mixtures were estimated for H. asiaticum. The CTCs of lambda-cyhalothrin + etoxazole and lambda-cyhalothrin + fipronil were 128.83 and 331.58, respectively, each demonstrating synergism. The results indicated that these two mixtures were more effective than individual insecticides, and this study suggests a substitutional approach to the control of ticks.

Acaricidal Activity of Tea Tree and Lemon Oil Nanoemulsions against Rhipicephalus annulatus

Tick infestation is a serious problem in many countries since it has an impact on the health of animals used for food production and pets, and frequently affects humans. Therefore, the present study aimed to investigate the acaricidal effects of nanoemulsions of essential oils of Melaleuca alternifolia (tea tree, TT) and Citrus limon (lemon oil, CL) against the different stages (adult, eggs, and larvae) of deltamethrin-resistant Rhipicephalus annulatus ticks. Three forms of these oils were tested: pure oils, nanoemulsions, and a binary combination. Tea tree and lemon oil nanoemulsions were prepared, and their properties were assessed using a zeta droplet size measurement and a UV-Vis spectrophotometer. The results showed that TT and CL exhibited higher adulticidal effects in their pure forms than in their nanoemulsion forms, as demonstrated by the lower concentrations required to achieve LC₅₀ (2.05 and 1.26%, vs. 12.8 and 11.4%, respectively) and LC₉₀ (4.01% and 2.62%, vs. 20.8 and 19.9%, respectively). Significant larvicidal activity was induced by the TTCL combination, and LC₅₀ was reached at a lower concentration (0.79%) than that required for the pure and nanoemulsion forms. The use of pure CL oil was found to have the most effective ovicidal effects. In conclusion, pure TT and CL have potent acaricidal effects against phenotypically resistant R. annulatus isolates. It is interesting that the activity levels of TT and CL EOs' binary and nanoemulsion forms were lower than those of their individual pure forms.

Dual assessment of transcriptional and metabolomic responses in the American dog tick following exposure to different pesticides and repellents

The American dog tick, Dermacentor variabilis, is a major pest to humans and animals, serving as a vector to Rickettsia rickettsii, a bacterium responsible for Rocky Mountain spotted fever, and Francisella tularensis, which is responsible for tularemia. Although several tactics for management have been deployed, very little is known about the molecular response following pesticidal treatments in ticks. In this study, we used a combined approach utilizing transcriptomics and metabolomics to understand the response of the American dog tick to five common pesticides (amitraz, chlorpyrifos, fipronil, permethrin, and propoxur), and analyzed previous experimental data utilizing DEET repellent. Exposure to different chemicals led to significant differential expression of a varying number of transcripts, where 42 were downregulated and only one was upregulated across all treatments. A metabolomic analysis identified significant changes in acetate and aspartate levels following exposure to chlorpyrifos and propoxur, which was attributed to reduced cholinesterase activity. Integrating the metabolomics study with RNA-seq analysis, we found the physiological manifestations of the combined metabolic and transcriptional differences, revealing several novel biomolecular pathways. In particular, we discovered the downregulation of amino sugar metabolism and methylhistidine metabolism after permethrin exposure, as well as an upregulation of glutamate metabolism in amitraz treated samples. Understanding these altered biochemical pathways following pesticide and repellent exposure can help us formulate more effective chemical treatments to reduce the burden of ticks.

Acaricides Resistance in Ticks: Selection, Diagnosis, Mechanisms, and Mitigation

Ticks are blood-feeding ecto-parasites that have a cosmopolitan distribution in tropical and subtropical regions of the world. Ticks cause economic losses in the form of reduced blood, meat and dairy products, as well as pathogen transmission. Different acaricides such as organochlorines, organophosphates, formamidines (e.g. amitraz), synthetic pyrethroids, macrocyclic lactones, fipronil, and fluazuron are currently used sequentially or simultaneously to control tick infestations. Most acaricide treatments now face increasingly high chances of failure, due to the resistance selection in different tick populations against these drugs. Acaricide resistance in ticks can be developed in different ways, including amino acid substitutions that result in morphological changes in the acaricide target, metabolic detoxification, and reduced acaricide entry through the outer layer of the tick body. The current literature brings a plethora of information regarding the use of different acaricides for tick control, resistance selection, analysis of mutations in target sites, and resistance mitigation. Alternatives such as synergistic use of different acaricides, plant-derived phytochemicals, fungi as biological control agents, and anti-tick vaccines have been recommended to avoid and mitigate acaricide resistance. The purpose of this review was to summarize and discuss different acaricides applied for tick control, their mechanisms of action and resistance selection, genetic polymorphisms in their target molecules, as well as the approaches used for diagnosis and mitigation of acaricide resistance, specifically in Rhipicephalus microplus ticks.

Pyrokinin receptor silencing in females of the southern cattle tick Rhipicephalus (Boophilus) microplus is associated with a reproductive fitness cost

Background

Rhipicephalusmicroplus is the vector of deadly cattle pathogens, especially Babesia spp., for which a recombinant vaccine is not available. Therefore, disease control depends on tick vector control. However, R.microplus populations worldwide have developed resistance to available acaricides, prompting the search for novel acaricide targets. G protein-coupled receptors (GPCRs) are involved in the regulation of many physiological processes and have been suggested as druggable targets for the control of arthropod vectors. Arthropod-specific signaling systems of small neuropeptides are being investigated for this purpose. The pyrokinin receptor (PKR) is a GPCR previously characterized in ticks. Myotropic activity of pyrokinins in feeding-related tissues of Rhipicephalussanguineus and Ixodesscapularis was recently reported.

Methods

The R.microplus pyrokinin receptor (Rhimi-PKR) was silenced through RNA interference (RNAi) in female ticks. To optimize RNAi, a dual-luciferase assay was applied to determine the silencing efficiency of two Rhimi-PKR double-stranded RNAs (dsRNA) prior to injecting dsRNA in ticks to be placed on cattle. Phenotypic variables of female ticks obtained at the endpoint of the RNAi experiment were compared to those of control female ticks (non-injected and beta-lactamase dsRNA-injected). Rhimi-PKR silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues.

Results

The Rhimi-PKR transcript was expressed in all developmental stages. Rhimi-PKR silencing was confirmed in whole ticks 4 days after injection, and in the tick carcass, ovary and synganglion 6 days after injection. Rhimi-PKR silencing was associated with an increased mortality and decreased weight of both surviving females and egg masses (P < 0.05). Delays in repletion, pre-oviposition and incubation periods were observed (P < 0.05).

Conclusions

Rhimi-PKR silencing negatively affected female reproductive fitness. The PKR appears to be directly or indirectly associated with the regulation of female feeding and/or reproductive output in R.microplus. Antagonists of the pyrokinin signaling system could be explored for tick control.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05349-w.

Efficacy of oral fluralaner (Bravecto) against Tunga penetrans in dogs: A negative control, randomized field study in an endemic community in Brazil

The sand flea Tunga penetrans is one of the zoonotic agents of tungiasis, a parasitic skin disease of humans and animals. The dog is one of its main reservoirs. This negatively controlled, randomized, double-masked clinical trial evaluated the therapeutic and residual efficacy of fluralaner for treatment of dogs naturally infested with T. penetrans. Sixty-two dogs from an endemically affected community in Brazil were randomly assigned to either receive oral fluralaner (Bravecto chewable tablets) at a dose of 25 to 56 mg fluralaner/kg body weight, or no treatment (31 dogs per group). Dogs were clinically examined using a severity score for acute canine tungiasis (SCADT), parasitological examinations as defined by the Fortaleza classification, and pictures of lesions on days 0 (inclusion and treatment), 7 ± 2, 14 ± 2, 21 ± 2, 28 ± 2, 60 ± 7, 90 ± 7, 120 ± 7 and 150 ± 7. The percentage of parasite-free dogs after treatment was >90% between days 14 and 90 post-treatment with 100% efficacy on study days 21, 28 and 60. Sand flea counts on fluralaner treated dogs were significantly lower (p<0.025) than control dogs on all counts from day 7 to 120. The number of live sand fleas on treated dogs was reduced by > 90% on day 7, > 95% on days 14 and 90, and 100% from day 21 to 60, and with a significant difference between groups from day 7 to 120. From day 7 to day 120, mean SCADT scores were significantly reduced in treated dogs with a mean of 0.10 compared to 1.54 on day 120 in untreated dogs. Therefore, a single oral fluralaner administration is effective for treating and achieving long lasting (> 12 weeks) prevention for tungiasis in dogs.

Tungiasis is a dermatological disease that affects humans and animals infested with sand fleas (Tunga spp.), especially in communities exposed to contaminated sandy and dry soil, where living conditions are precarious and access to basic health is limited. These sand fleas penetrate host skin and cause severe acute and chronic injuries that can dramatically compromise the host’s health. Dogs are a primary reservoir and disseminator of these fleas in South America. In this clinical field trial, the efficacy of a single oral dose of fluralaner (Bravecto chewable tablets) was evaluated for treatment and prevention of tungiasis in dogs in an endemic area of Brazil. The treatment was assessed through absence of live sand fleas and resolution of characteristic tungiasis skin lesions. Fluralaner was 100% effective from the third to the eighth week post-treatment, eliminated live sand fleas and protected against new infestations during the study. Therefore, fluralaner proved to be an excellent therapeutic option for treatment and a highly effective control option for canine tungiasis.

Using Proteomic Approaches to Unravel the Response of Ctenocephalides felis felis to Blood Feeding and Infection With Bartonella henselae

Among the Ctenocephalides felis felis-borne pathogens, Bartonella henselae, the main aetiological agent of cat scratch disease (CSD), is of increasing comparative biomedical importance. Despite the importance of B. henselae as an emergent pathogen, prevention of the diseases caused by this agent in cats, dogs and humans mostly relies on the use of ectoparasiticides. A vaccine targeting both flea fitness and pathogen competence is an attractive choice requiring the identification of flea proteins/metabolites with a dual effect. Even though recent developments in vector and pathogen -omics have advanced the understanding of the genetic factors and molecular pathways involved at the tick-pathogen interface, leading to discovery of candidate protective antigens, only a few studies have focused on the interaction between fleas and flea-borne pathogens. Taking into account the period of time needed for B. henselae replication in flea digestive tract, the present study investigated flea-differentially abundant proteins (FDAP) in unfed fleas, fleas fed on uninfected cats, and fleas fed on B. henselae-infected cats at 24 hours and 9 days after the beginning of blood feeding. Proteomics approaches were designed and implemented to interrogate differentially expressed proteins, so as to gain a better understanding of proteomic changes associated with the initial B. henselae transmission period (24 hour timepoint) and a subsequent time point 9 days after blood ingestion and flea infection. As a result, serine proteases, ribosomal proteins, proteasome subunit α-type, juvenile hormone epoxide hydrolase 1, vitellogenin C, allantoinase, phosphoenolpyruvate carboxykinase, succinic semialdehyde dehydrogenase, glycinamide ribotide transformylase, secreted salivary acid phosphatase had high abundance in response of C. felis blood feeding and/or infection by B. henselae. In contrast, high abundance of serpin-1, arginine kinase, ribosomal proteins, peritrophin-like protein, and FS-H/FSI antigen family member 3 was strongly associated with unfed cat fleas. Findings from this study provide insights into proteomic response of cat fleas to B. henselae infected and uninfected blood meal, as well as C. felis response to invading B. henselae over an infection time course, thus helping understand the complex interactions between cat fleas and B. henselae at protein levels.

Pyrethroids resistance in Pulex irritans and Ctenocephalides canis in west and northwest Iran

Resistance to the knockdown effect of pyrethroid insecticides occurs due to mutations at target sites of pyrethroids, meaning the voltage-gated sodium channels gene (VGSC) in the membrane of the neurons. In fleas, this mutation occurs at two sites in the sodium channel in neurons: one is the replacement of leucine with phenylalanine (L1014F) and the other is the replacement of threonine with valine (T929V). In this study, 81 Pulex irritans and 47 Ctenocephalides canis fleas were collected from five provinces in the west and northwest of Iran. Adult fleas were exposed to cypermethrin 0.75%, and the mortality rate was calculated after 1 and 8 hr, and the mutation sites in the VGSC gene were investigated. The lethality of cypermethrin 0.75% for P. irritans was 40.00 - 57.14% after 1 hr and 60.00 - 73.91% after 8 hr. The lethality of this dose for C. canis after 1 and 8 hr of exposure was 33.33 - 41.17% and 66.66 - 80.33%, respectively. The VGSC sequence analysis indicated two mutation sites in the resistant and one mutation site in the susceptible fleas. The VGSC sequence analysis of susceptible P. irritans showed that 5.50% of them were homozygous susceptible and 94.45% were hetero-zygous susceptible. Susceptible C. canis were 5.26% homozygous and 94.73% heterozygous susceptible. All the resistant fleas were homozygous. The development of pyrethroid resistance and high-frequency L1014F mutation in fleas suggest that pyrethroids are likely to be ineffective in controlling fleas. Therefore, monitoring pyrethroid resistance and its underlying mechanisms are necessary for controlling fleas and finding new alternative control methods.

Genotyping of Deltamethrin Resistance in Rhipicephalus (Boophilus) microplus Population in Kerala, South India

PURPOSE

Genotyping of Rhipicephalus (Boophilus) microplus for polymorphisms in deltamethrin-resistant loci of sodium channel gene by allele-specific PCR (AS-PCR).

METHODS

Adult R. (B.) microplus ticks were collected from naturally infested cattle in Kerala. The larval packet test (LPT) was performed with deltamethrin and dose response data were analysed by probit method. Adult and larval tick DNA were amplified by PCR and later sequenced to identify mutations, if any, in the domain II S4-5 linker and domain III S6 regions in para voltage-gated sodium channel gene, at loci that were previously documented to be associated with deltamethrin resistance. Allele-specific PCR was performed for the amplification of target gene locus (C190A and T2134C) to genotype 1000 larvae each, at these loci. Genotype frequency was statistically analysed by Chi-square test.

RESULTS

Bioassay using LPT revealed that LC₅₀ and LC₉₅ values of all the R. (B.) microplus isolates in this study were more than double the reported values of reference susceptible strain. Sequence analysis of the PCR amplicons of domain II S4-5 linker of voltage-gated sodium channel gene revealed C190A mutation, A271G mutation as well as A-G mutation at 217th position. AS-PCR done to genotype C190A mutations revealed a frequency of 6%, 15% and 64%, respectively for homozygous-susceptible (SS), heterozygous (RS) and homozygous-resistant (RR) genotypes. In domain III S6 region of the gene, C2121T and A2102T mutations were observed. AS-PCR to genotype the previously reported T2134C mutation revealed 100% SS genotype in R. (B.) microplus isolates of Kerala.

CONCLUSIONS

Genotyping of R. (B.) microplus isolates of Kerala for target site mutations reportedly associated with deltamethrin resistance revealed a significantly high frequency of resistant genotypes at II S4-5 linker of voltage-gated sodium channel gene. This study forms the first report of such mutations in Kerala, south India and demands serious attention in the light of increased prevalence of tick-borne haemoparasitic infection.

Susceptibility of Ixodes scapularis (Acari: Ixodidae) to Permethrin Under a Long-Term 4-Poster Deer Treatment Area on Shelter Island, NY

Pesticide resistance in medically significant disease vectors can negatively impact the efficacy of control efforts. Resistance research on ticks has focused primarily on species of veterinary significance that experience relatively high degrees of control pressure. Resistance in tick vectors of medical significance has received little attention, in part because area-wide pesticide applications are not used to control these generalist tick species. One of the few effective methods currently used for area-wide control of medically important ticks, including Ixodes scapularis Say (Acari: Ixodidae), is deployment of 4-poster devices. Deer self-apply a topical acaricide (permethrin) while feeding on corn from the devices. A 4-poster program using permethrin has been deployed on Shelter Island, NY to control I. scapularis populations since 2008. We collected engorged female ticks from deer in this management area and a location in the Mid-Hudson River Valley, NY without area-wide tick control. Larvae were reared from egg masses and their susceptibility to permethrin was tested. Larvae originating from a long-term laboratory colony were used as a susceptible baseline for comparison. Compared against the laboratory colony, resistance ratios at LC-50 for Shelter Island and Hudson Valley I. scapularis were 1.87 and 1.51, respectively. The susceptibilities of the field populations to permethrin were significantly lower than that of the colony ticks. We provide the first data using the larval packet test to establish baseline susceptibility for I. scapularis to permethrin along with information relevant to understanding resistance emergence in tick populations under sustained control pressure from 4-poster devices.

Mechanisms of amitraz resistance in a Rhipicephalus microplus strain from southern Brazil

Amitraz is one of the most used acaricides for the control of ticks of domestic animals, however, extensive use of this active ingredient has favored the development of resistant populations of Rhipicephalus microplus worldwide. The possible mechanisms of metabolic and/or target-site alterations mechanisms of amitraz resistance were investigated in a Brazilian field population of R. microplus (São Gabriel strain). Bioassays with the synergists piperonylbutoxide, triphenylphosphate and diethyl-maleate were used to evaluate the metabolic mechanisms involved. Target-site insensitivity was investigated by amplification and sequencing of a fragment of the octopamine/tyramine (OCT/TYR) receptor gene. Piperonylbutoxide synergism (synergism ratio = 2.8) indicated the participation of the P450 pathway in the detoxification of amitraz. Previously reported single nucleotide polymorphisms that confer amino acid changes in the OCT/TYR receptor, threonine to proline (T8P) and leucine to serine (L22S), were found in the amitraz-resistant strain but not in the susceptible reference strain. The results suggest that amitraz resistance in the studied strain is multi-factorial and may result from cytochrome P450 detoxification and mutations in octopamine receptors.

Analysis of gaps in feline ectoparasiticide purchases from veterinary clinics in the United States

Background

The study objective was to examine cat owner ectoparasiticide purchases in the United States and estimate the impact of purchase gaps on timely ectoparasite protection administration. These purchase gaps lead to periods of time when cats are unprotected from ectoparasites.

Methods

Ectoparasiticide purchase transactions for individual cats from 671 U.S. veterinary clinics from January 1, 2017 through June 30, 2019 were evaluated to determine time “gaps” between doses of ectoparasiticides purchased in a defined 12-month period. Ectoparasiticides examined were topically applied products that contained fluralaner, fipronil/(S)-methoprene/pyriproxyfen, imidacloprid/pyriproxyfen or selamectin as active ingredients. The duration of protection following administration of one dose was 8–12 weeks for the fluralaner-containing product and one month for the other products.

Results

Ectoparasiticide purchase records were obtained from 114,853 cat owners and analysis found that most owners bought ≤ 6 months of protection during the year, with 61–75% (depending on the product) purchasing just 1–3 months of protection. The size of the average purchase gap was determined for all dose combinations out to 12 months of protection (5–7 doses for fluralaner and 12 doses for the other three products dosed monthly. The largest gaps occurred between the first and second doses and the second and third doses. Average purchase gaps for the four different products between doses 1 and 2 ranged from 11.2 to 13.9 weeks and between doses 2 and 3 ranged from 7.7 to 12.2 weeks. The fraction of purchases separated by gaps and the average length of the gap tended to decrease with increasing number of doses purchased. Owners purchasing the 8 to 12-week duration product containing fluralaner provided ectoparasite protection (“doses plus gap period”) for a larger proportion of each 2-dose period compared with owners purchasing products administered monthly.

Conclusions

When cat owners purchase flea and tick medication, gaps between subsequent purchases reduces the proportion of time ectoparasite protection can be provided. The duration of the gap between doses has an impact on the effectiveness of flea/tick medication because it inserts a period without flea and tick protection between doses of flea and tick medication. The gaps between purchases were shorter and the period of ectoparasite protection was larger for owners purchasing a 12-week product than for owners purchasing a monthly product.

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.

Vaccine approaches applied to controlling dog ticks

Ticks are considered the most important vectors in veterinary medicine with a profound impact on animal health worldwide, as well as being key vectors of diseases affecting household pets. The leading strategy applied to dog tick control is the continued use of acaricides. However, this approach is not sustainable due to surging tick resistance, growing public concern over pesticide residues in food and in the environment, and the rising costs associated with their development. In contrast, tick vaccines are a cost-effective and environmentally friendly alternative against tick-borne diseases by controlling vector infestations and reducing pathogen transmission. These premises have encouraged researchers to develop an effective vaccine against ticks, with several proteins having been characterized and used in native, synthetic, and recombinant forms as antigens in immunizations. The growing interaction between domestic pets and people underscores the importance of developing new tick control measures that require effective screening platforms applied to vaccine development. However, as reviewed in this paper, very little progress has been made in controlling ectoparasite infestations in pets using the vaccine approach. The control of tick infestations and pathogen transmission could be obtained through immunization programs aimed at reducing the tick population and interfering in the pathogenic transmission that affects human and animal health on a global scale.

Protecting dogs and cats against the Australian paralysis tick, Ixodes holocyclus (Acari: Ixodidae): A review of the Australian acaricide registration process

Tick control is mainly achieved through the use of effective ectoparasiticides that can be either dermally or systemically distributed in/on the host. Before any acaricide can be legally made available to veterinarians and pet owners, it must demonstrate efficacy in a series of well-designed dose confirmation studies. The data generated during these studies are then reviewed by government regulators and used for the registration of the acaricide. In Australia, the most significant tick species is the Australian paralysis tick, Ixodes holocyclus. This three-host tick produces a potent neurotoxin (holocyclotoxin) that induces a rapidly ascending flaccid paralysis that can be fatal to companion animals and larger mammals such as cattle and horses. The Australian Pesticides and Veterinary Medicines Authority (APVMA) is the national Australian regulator which sets the data requirements for the registration of acaricides. This paper reviews the requirements set by the APVMA and puts them in direct context with the biology, distribution and reported acaricide susceptibility of I. holocyclus. An overview of acaricides currently registered in Australia for the control of I. holocyclus in dogs and cats, their reported efficacy data and the conduct of I. holocyclus efficacy trials are also provided.

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A review of the requirements for the conduct of acaricide efficacy trials for Ixodes holocyclus was undertaken.

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The requirements of the Australian government regulator were put in direct context with the biology of the species.

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The need for the inclusion of Far North Queensland ticks into tick studies needs to be further assessed.

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At present, there is no evidence of acaricide resistance in Ixodes holocyclus.

Hyalomma anatolicum resistance against ivermectin and fipronil is associated with indiscriminate use of acaricides in southwestern Balochistan, Pakistan

Ivermectin and fipronil have been used regularly to control the hard tick Hyalomma anatolicum (Acari: Ixodidae) in domestic ruminants for more than a half-decade in Balochistan, Pakistan. Inappropriate and indiscriminate use of these acaricides has resulted in the development of resistances in tick species. In this work, acaricides (ivermectin and fipronil) resistance was evaluated in H. anatolicum through in vitro and in vivo bioassays in a horse farm of Quetta, Balochistan province, Pakistan. A participatory epidemiological survey was conducted to assess potential risk factors associated with the development of acaricide resistance in H. anatolicum. The results of the epidemiological survey revealed that the horse keepers did not follow the manufacturer's instructions for the use of acaricides and applied indiscriminate doses of acaricides. The results of in vitro bioassays (adult immersion test and larval immersion test) showed that fipronil and ivermectin have protective efficacy against H. anatolicum. The results of in vivo bioassay (adult-tick mortality assay) revealed that fipronil had a higher efficacy (78.16%) than ivermectin (49.94%). More than 80% of tick mortality was not achieved in any bioassays, even for the highest acaricide concentration (100 ppm), which suggests the development of acaricide resistance against fipronil and ivermectin. This study highlights the urgency to implement a country-wide awareness about resistance monitoring and effective tick control. Graphical abstract.

General Considerations for On-Animal Ectoparasiticidal Product Evaluations

Successfully preparing for and conducting on-animal ectoparasiticidal evaluations is key in providing accurate results and inferences on product performance. However, the procedures associated with designing sound-reliable research projects while using animal test subjects can become complex. The current manuscript offers insights towards the characterization of different evaluation types highlighting key considerations and potential problematic barriers that may otherwise be overlooked by researchers new to the area of on-animal product evaluation. Furthermore, recommendations on reporting inferences from findings based on various study designs are discussed. The authors of the current manuscript offer these considerations in the hopes of maintaining harmony in future reports used to develop and evaluate on-animal ectoparsiticidal products in the field of veterinary entomology.

Adherence to veterinary recommendations for ectoparasiticides purchased by cat owners in the USA

Background

Safe and effective flea and tick treatment options for cats are important in companion animal practice because of feline ectoparasite infestation prevalence and the potential for parasitic disease transmission. Retrospective cat owner purchasing transactions at United States of America (USA) veterinary clinics were obtained for three topical feline flea and tick ectoparasiticides. One medication, fluralaner, had a 12-week redosing interval, while two other medications (fipronil/s-methoprene/pyriproxyfen; imidacloprid/pyriproxyfen) were approved for monthly redosing. The annual number of doses purchased by cat owners was determined for each of the three medications and then compared between medications. The objective was to evaluate whether 12-week retreatment intervals resulted in a different duration of coverage compared to monthly treatments for ectoparasiticide products.

Methods

Study results were obtained by analyzing the transactional records from a commercial database derived from veterinary practice management software. The study database consisted of cat owner purchasing records from January 2017 through June 2019 from 671 veterinary practices representing 41,630 cats.

Results

Cat owners purchased an average of 1.5 doses of fluralaner per year which, based on a 12-week redosing interval, provides 4.2 months of treatment coverage. Cat owners who used monthly flea and tick medications respectively purchased 3.6 months (fipronil/s-methoprene/pyriproxyfen combination) and 2.8 months (imidacloprid/pyriproxyfen) annually of each of the two medications. Average yearly cat owner purchases of fluralaner provide a significantly longer duration of coverage than for cat owners purchasing fipronil/s-methoprene/pyriproxyfen (17% more) or imidacloprid/pyriproxyfen (50% more).

Conclusions

Cat owners who obtained a flea and tick treatment with a 12-week redosing interval (fluralaner) protected their cats for up to 17% or 50% longer duration each year, respectively, compared to the duration of protection obtained by cat owners who used a medication re-dosed monthly. Cat owners should increase their duration of flea and tick coverage to come closer to achieving veterinary recommendations.

A Survey of Ticks Infesting Dogs and Cats in Ireland

Ticks are important ectoparasites of dogs and cats. Infestations can result in itching and localised dermatitis. In addition, ticks can act as vector of a range of viral, bacterial and protozoal pathogens. This paper reports the results of a nationwide survey of ticks infesting dogs and cats in Ireland. Seventy veterinary practices submitted a total of 120 ticks collected from 56 dogs and 16 cats. Ixodes ricinus was the most abundant species on dogs while Ixodes hexagonus was the most abundant species on cats. The remainder were identified as Ixodes canisuga and a single Rhipicephalus sanguineus specimen. The garden was most frequently associated with tick exposure in both dogs and cats. Sporting dog breeds (n = 17; 31%) were more likely to be infested with ticks than any other breed. Nearly all (n = 56; 95%) veterinarians indicated that ticks are a concern to their clients when they are found on their pets. Pet owners used a variety of products to control ectoparasites on their animals but a significant number (n = 18, 31%) indicated that they felt that the products are less effective highlighting the need for further investigations. Field sampling indicated that ticks are present at a low level in much of the greater Dublin area.

Botanical acaricides induced morphophysiological changes of reproductive and salivary glands in tick: A mini-review

Ticks are obligate hematophagous ectoparasites and important vectors of several pathogens of medical and veterinary significance, in addition to economic losses associated with their infestation. The primary method for the current control of tick is the use of synthetic acaricides, and many studies have focused on the tick control efficacy associated with the use of synthetic acaricides. However, the intensive use of these compounds has environmental and public health implications, in addition to the development of resistant tick populations. Over the years, studies have demonstrated the great potential of botanicals as an effective alternative in tick control. Most of the reviews on the acaricidal activity of botanicals focused on the effects relating to the development, reproduction, and mortality rate of ticks. Besides this acaricidal activity, botanicals can also affect the morphophysiology of the reproductive organs and the salivary glands that are important for tick procreation and survival. Effects relating to histopathological and cell ultra-structural alterations caused by botanical acaricides can be determined through microscopy techniques. Hence, the present mini-review focuses on studies dealing with morphophysiology changes of the reproductive system and the salivary gland of ticks exposed to botanical acaricides, with a view of expanding our knowledge for the future integrative application of botanical acaricides in tick control.

Botanical acaricides and repellents in tick control: current status and future directions

Ticks are obligate blood-sucking ectoparasites and notorious as vectors of a great diversity of, in many instances, zoonotic pathogens which can cause considerable damage to animal and human health. The most commonly used approach for the control of ticks is the application of synthetic acaricides. However, the negative impacts of synthetic acaricides on the treated animals and the environment, in addition to its documented role in the development of resistance has led to the search for safer and more environmentally friendly alternative methods without compromising efficacy. An emerging promising approach for the control of ticks which has attracted much attention in recent years is the use of botanicals. Indeed, botanicals have been widely reported to show diverse effects and great potential as tick repellent and control. Although several excellent reviews have previously focused on this topic, studies on the exploration and application of botanicals to control ticks have expanded rapidly. Herein, we provide an update on the current understanding and status of botanical acaricides and repellents in tick control using recently published articles between 2017 and 2019. We also discuss the challenges and future directions in the application of botanicals in tick control, with a view of providing important clues for designing new integrated tick control methods.

Fipronil Tablets: Development and Pharmacokinetic Profile in Beagle Dogs

Increased human-pet interactions have led to concerns related to the prevention and treatment of ectoparasite infestations. Fipronil (FIP) is a widely used ectoparasiticide in veterinary medicine available for topical administration; however, its use may cause damage to the owners and the environment. The aim of the study was to develop immediate-release tablets of FIP, as well as to determine its pharmacokinetic properties after oral administration in beagle dogs. The prepared FIP tablets were evaluated for pre-compression (angle of repose, speed flow, and Carr's index) and post-compression (weight variation, friability, thickness, hardness, disintegration time, and dissolution rate) parameters. Orally administered FIP at a dose of 2 mg/kg was rapidly absorbed with C_máx of 3.13 ± 1.39 μg/mL at 1.83 ± 0.40 h post treatment (P.T.) and metabolized with 1.27 ± 1.04 μg/mL at 2.33 ± 0.82 h P.T. for fipronil sulfone (SULF) (the primary metabolite). The elimination of FIP and SULF occurred slowly and had maintained quantifiable plasma levels in the blood for up to 28 days P.T. The goal of the study is aligned with the concept of One Health, which aims to collaboratively achieve the best health for people, animals, and the environment. Therefore, the use of FIP tablets for the control of ectoparasites in dogs may be a safer alternative for owners and the environment.

Innovative way to dispense pheromones for off-host control of Rhipicephalus sanguineus sensu lato ticks

Vapour patches dispensing pheromones were evaluated as lures to increase the attractiveness of sticky tick traps for Rhipicephalus sanguineus sensu lato (s.l.). Sex pheromone (SP), assembly pheromone (AP) and a combination of SP + AP at optimal concentrations were impregnated in vapour patches. The responses of the different stages of R. sanguineus s.l. (i.e. larvae, nymphs and adults) to the pheromones were evaluated using a Petri dish bioassay. The impregnated vapour patches were retained as such for a period of two mo and their efficacy was reassessed. In a subsequent field trial, pheromone impregnated vapour patches were placed as lures in bamboo (Bambusa vulgaris) sticky traps designed for the control of ticks in dog kennels. In vitro AP impregnated vapour patches were effective in attracting the different life stages of R. sanguineus s.l. whereas SP was effective in attracting the unfed and fed male stages of R. sanguineus s.l. The field trial revealed that questing and engorged larvae, nymphs and females of R. sanguineus s.l. were attracted more towards AP impregnated vapour patches than SP and AP + SP impregnated vapour patches. Fed and unfed male ticks were lured effectively by SP alone. The combination of SP + AP revealed no potent additive or synergistic effect.

Efficacy of λ-cyhalothrin, amitraz, and phoxim against the poultry red mite Dermanyssus gallinae De Geer, 1778 (Mesostigmata: Dermanyssidae): an eight-year survey

Dermanyssus gallinae (De Geer, 1778) is a major problem for the poultry industry worldwide, as it negatively affects virtually all kinds of rearing systems. Therefore, the control of infestation has become a routine process, and its economic cost is constantly increasing. Until now, most of the control strategies have relied on the use of synthetic chemical drugs, but their efficacy is often questioned by the emergence and diffusion of resistant mite populations. With this in mind, the efficacy of λ-cyhalothrin, amitraz, and phoxim has been verified by testing them against 86 mite populations collected from the same number of poultry farms in Italy from 2008 to 2015. Assays were performed according to the filter paper method using the recommended, half, quarter, double and quadruple doses. The results showed that phoxim and amitraz were the most effective acaricides (median efficacies 80.35% and 80.83%, respectively), but amitraz exhibited a sharp fall in its efficacy during 2011 and 2012, while phoxim maintained its high effectiveness up to 2015, when it dropped. The overall median efficacy of λ-cyhalothrin was 58.33%. The data also highlighted the importance of the use of the right concentration, as an increase in dosage was not always useful against resistant populations, while its reduction also diminished efficacy, simultaneously increasing the risk for the development of resistance.

Efficacy of a spot-on combination of fluralaner plus moxidectin (Bravecto® Plus) in cats following repeated experimental challenge with a field isolate of Ctenocephalides felis

BACKGROUND

A spot-on formulation of fluralaner plus moxidectin has been designed to provide long-term protection against fleas and ticks, prevent heartworm disease and treat gastrointestinal nematode infections in cats. The objective of this study was to determine the efficacy of this product against fleas collected from a household with repeated fipronil failures following owner-administered treatments.

METHODS

Thirty cats were randomized to three equal groups: (A) untreated controls; (B) to receive a single application of fluralaner plus moxidectin (Bravecto® Plus) at 40 mg/kg and 2 mg/kg body weight, respectively; and (C) three applications at one month intervals with a spot-on formulation of fipronil and (S)-methoprene (Frontline® Plus) at 0.5 ml manufacturer recommended dose. Flea challenges were completed on Days -6 (for randomization), -1, 7, 14, 28, 42, 56, 70, 77, 84 and 91. Flea counts were completed 48 hours after initial treatment and 48 hours following each subsequent challenge.

RESULTS

Fleas were found on all control and all fipronil and (S)-methoprene treated cats at every assessment. From Day 2 to Day 93, all cats in the fluralaner plus moxidectin group were flea-free, with one exception (Day 58; three fleas counted on one cat); control group flea counts ranged between 34-109, and fipronil and (S)-methoprene group counts ranged between 1-79. At each assessment after Day 0, compared to the control group, geometric mean flea counts were significantly lower in the fipronil and (S)-methoprene group (P ≤ 0.04) and in the fluralaner plus moxidectin group (P < 0.001), and mean flea counts in the fluralaner plus moxidectin group were significantly lower than those of the fipronil and (S)-methoprene group (P < 0.001). The efficacy of fluralaner plus moxidectin, based on geometric means, was 100% at each assessment post-Day 0 except on Day 58 when efficacy was 99.7%. In the fipronil and (S)-methoprene group efficacy ranged between 30.6-65.6%.

CONCLUSIONS

These findings demonstrate complete efficacy of fluralaner plus moxidectin against a flea isolate that was not controlled by fipronil and (S)-methoprene. This study provides confirmation of the consistent, sustained efficacy of topically applied fluralaner in the treatment and control of flea infestations in cats.

Benzoylphenyl ureas as veterinary antiparasitics. An overview and outlook with emphasis on efficacy, usage and resistance

Six benzoylphenyl ureas are currently used in formulations approved as veterinary medicines: diflubenzuron for fly control mainly on cattle, lice and blowfly strike control on sheep, and lice control on farmed salmonids; lufenuron for flea control on dogs and cats and for lice control on farmed salmonids; triflumuron for lice and blowfly strike control on sheep; fluazuron for tick control on cattle; teflubenzuron for lice control on farmed salmon; and novaluron for fly and tick control on cattle and for flea control on dogs. Resistance to diflubenzuron and triflumuron has already been reported for sheep body lice and blowflies, and to fluazuron in cattle ticks. These and other minor veterinary usages, as well as the current status of resistance, are reviewed and perspectives for future opportunities are discussed based on unexplored potentials and threats posed by future resistance development.

Acaricidal efficacy of deltamethrin-zinc oxide nanocomposite on Rhipicephalus (Boophilus) annulatus tick

In the veterinary field, there is a great concern about the issue of acaricides resistance in cattle ticks. A comparative study was designed to evaluate the in vitro acaricidal efficacy of imidacloprid nano-emulsion, zinc oxide nanoparticles (ZnO NPs), silver nanoparticles (Ag NPs), deltamethrin, deltamethrin-ZnO NPs, and deltamethrin-Ag NPs. In addition, the novel formulations of deltamethrin (deltamethrin-ZnO NPs and deltamethrin-Ag NPs) against Rhipicephalus (Boophilus) annulatus were also evaluated by in vivo animal efficacy trials. Nanoparticles and their loaded forms, deltamethrin-Ag NPs and deltamethrin-ZnO NPs, were characterized by Transmission Electron Microscope (TEM) and Fourier-Transform Infrared Spectrum (FTIR). The adulticidal activity of deltamethrin-ZnO NPs at different concentrations; 2 mL/L, 1 mL/L, 0.5 mL/L and 0.25 mL/L induced a significant (P ≤ 0.05) lethal effect on adult ticks compared to deltamethrin-Ag NPs at the same concentrations. The larvicidal efficacy of deltamethrin-ZnO NPs resulted in a complete larval mortality within 24 h of exposure, while deltamethrin and deltamethrin-Ag NPs exhibited 100% immobility of larvae 48 h post-exposure. Furthermore, the in vivo experiments showed a considerable reduction in the tick's survival after using deltamethrin-ZnO NPs. There was no significant effect of different treatments on liver or kidney function tests at pre- and post-treatment of animals. In conclusion, deltamethrin-ZnO nanocomposite was the most effective adulticide and larvicide against R. (B.) annulatus. To the best of our knowledge, this is the first report for using deltamethrin-ZnO NPs as an acaricide.

Virulence of Aerial Conidia of Beauveria bassiana Produced under LED Light to Ctenocephalides felis (Cat Flea)

Ctenocephalides felis is an ectoparasitic flea species commonly found on dogs and cats. The current study verified the in vitro virulence of conidia of the entomopathogenic fungus Beauveria bassiana produced under different color LED light (red, blue, purple, green, yellow, and white) to adults of C. felis. The fungal isolates were cultivated on malt extract agar (MEA). Bioassay treatments used aerial conidia in test tubes. Adult fleas were obtained from a house cat in Chiang Mai province, Thailand. The experiments were composed of one control and eleven treatment groups. All of the treatments with B. bassiana conidia caused adult mortality after an exposure of 12 h. Among the conditions used in this study, B. bassiana cultured under red LED and fluorescent light were the most effective in causing mortality (100 %) in adult fleas after 36 h. The experimental results indicate that these aerial conidia of B. bassiana have promising potential for use in control of C. felis adult stages.

Preferences of Pet Owners in Regard to the Use of Insecticides for Flea Control

A survey conducted from 2002 to 2012 of 759 customers from 84 veterinary practices allows us to examine the habits of dog and cat owners regarding the use of insecticides for flea control. The results indicate that the percentage of animals treated during the 12 mo prior to the survey was not very high (71% in dogs and 50% in cats), considering that 100% of animals included in the study were flea-infested. Statistical analysis shows that animals older than 4 mo are treated more frequently and that dogs are more likely to be treated than cats. Among cats, those living in houses with gardens or farms are treated at a higher rate than those that live in houses without gardens or in flats. The main variable associated with the degree of satisfaction and product loyalty is the active ingredient, and the choice of a commercial product is generally associated with high-efficacy products. The mode of application of a flea treatment does not seem to have a strong influence on pet owner satisfaction or loyalty. Likewise, we do not find a clear correlation between owners' satisfaction and loyalty, so pet owners may find the results of the selected product more or less satisfactory for reasons other than simple effectiveness. Finally, because of the complexity of the life cycle of these ectoparasites, the importance of the advice of a veterinarian when planning flea control is emphasized.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Field evaluation of a 0.005% fipronil bait, orally administered to Rhombomys opimus, for control of fleas (Siphonaptera: Pulicidae) and phlebotomine sand flies (Diptera: Psychodidae) in the Central Asian Republic of Kazakhstan

Plague (Yersinia pestis) and zoonotic cutaneous leishmaniasis (Leishmania major) are two rodent-associated diseases which are vectored by fleas and phlebotomine sand flies, respectively. In Central Asia, the great gerbil (Rhombomys opimus) serves as the primary reservoir for both diseases in most natural foci. The systemic insecticide fipronil has been previously shown to be highly effective in controlling fleas and sand flies. However, the impact of a fipronil-based rodent bait, on flea and sand fly abundance, has never been reported in Central Asia. A field trial was conducted in southeastern Kazakhstan to evaluate the efficacy of a 0.005% fipronil bait, applied to gerbil burrows for oral uptake, in reducing Xenopsylla spp. flea and Phlebotomus spp. sand fly abundance. All active gerbil burrows within the treated area were presented with ~120 g of 0.005% fipronil grain bait twice during late spring/early summer (June 16, June 21). In total, 120 occupied and 14 visited gerbil colonies were surveyed and treated, and the resulting application rate was minimal (~0.006 mg fipronil/m2). The bait resulted in 100% reduction in Xenopsylla spp. flea abundance at 80-days post-treatment. Gravid sand flies were reduced ~72% and 100% during treatment and at week-3 post-treatment, respectively. However, noticeable sand fly reduction did not occur after week-3 and results suggest environmental factors also influenced abundance significantly. In conclusion, fipronil bait, applied in southeastern Kazakhstan, has the potential to reduce or potentially eliminate Xenopsylla spp. fleas if applied at least every 80-days, but may need to be applied at higher frequency to significantly reduce the oviposition rate of Phlebotomus spp. sand flies. Fipronil-based bait may provide a means of controlling blood-feeding vectors, subsequently reducing disease risk, in Central Asia and other affected regions globally.

First report of target site insensitivity to pyrethroids in human flea, Pulex irritans (Siphonaptera: Pulicidae)

The human flea, Pulex irritans, is the most important ectoparasite of humans. Intensive use of pyrethroids for its control has led to insecticide resistance. Monitoring pyrethroid resistance and its underlying mechanisms is essential for flea control. The aims of this study were to identify the susceptibility status of human flea to permethrin and to detect the presence of knockdown resistance (kdr) mutation and its frequency in populations of P. irritans. Adults of P. irritans were collected from Zanjan Province, northwest of Iran, during 2013-2017. Different populations of this flea were exposed to permethrin 0.75% for one and 8 h and then the mortality rate, as well as KD₅₀ and KD₉₅ times were calculated. Total RNA and gDNA of samples were extracted, and the fragments of cDNA encoding the partial voltage-gated sodium channel (VGSC) peptides were amplified using degenerated primers. Specific PCR and TaqMan real-time assays were conducted to characterize the vgsc gene and to detect the presence of mutation and genotyping of the populations. Mortality rates were in the range from 32% to 67% for one-hour and 73% to 90% for eight-hour exposure to permethrin 0.75%. KD₅₀ and KD₉₅ times varied in a range from 46 to 241 and 177 to 899 min, respectively. Sequencing of 70 amplified fragments of gDNA resulted in a 578-bp product. These fragments contained two introns (92 and 63 bp) and three exons (141, 189, and 92 bp) encoding 138 amino acids that encompassed IIS4-IIS6 and the partial linker between domains II and III of VGSC. All the studied populations showed L1014F mutation, substitution of CTT for TTT at the 1014 allele. The result of TaqMan assay for 624 samples showed 96.6% homogenous and 3.36% heterozygous mutant. The development of permethrin resistance and the presence of the L1014F mutation at high frequency in flea populations indicate that pyrethroids are likely ineffective in controlling human flea. Therefore, novel alternative control methods are needed to combat this human ectoparasite.

Disruption of blood meal-responsive serpins prevents Ixodes scapularis from feeding to repletion

Serine protease inhibitors (serpins) are thought to mediate the tick's evasion of the host's serine protease-mediated defense pathways such as inflammation and blood clotting. This study describes characterization and target validation of 11 blood meal-responsive serpins that are associated with nymph and adult Ixodes scapularis tick feeding as revealed by quantitative (q)RT-PCR and RNAi silencing analyses. Given the high number of targets, we used combinatorial (co) RNAi silencing to disrupt candidate serpins in two groups (G): seven highly identical and four non-identical serpins based on amino acid identities, here after called GI and GII respectively. We show that injection of both GI and GII co-dsRNA into unfed nymph and adult I. scapularis ticks triggered suppression of cognate serpin mRNA. We show that disruption of GII, but not GI serpins significantly reduced feeding efficiency of both nymph and adult I. scapularis ticks. Knockdown of GII serpin transcripts caused significant respective mortalities of ≤40 and 71% of nymphal and adult ticks that occurred within 24-48 h of attachment. This is significant, as the observed lethality preceded the tick feeding period when transmission of tick borne pathogens is predominant. We suspect that some of the GII serpins (S9, S17, S19 and S32) play roles in the tick detachment process in that upon detachment, mouthparts of GII co-dsRNA injected were covered with a whitish gel-like tissue that could be the tick cement cone. Normally, ticks do not retain tissue on their mouthparts upon detachment. Furthermore, disruption of GII serpins reduced tick blood meal sizes and the adult tick's ability to convert the blood meal to eggs. We discuss our data with reference to tick feeding physiology and conclude that some of the GII serpins are potential targets for anti-tick vaccine development.

Repellence of essential oils and selected compounds against ticks-A systematic review

Ticks act as vectors of a wide range of infectious agents, far encompassing any other group of bloodsucking arthropods worldwide. The prevention of tick-borne diseases is strictly linked to the successful management of tick vector populations. The employ of repellents can represent a worth solution to avoid tick bites. It is widely adopted to protect travellers and pets exposed to ticks during limited periods of the year. The use of natural products as active ingredients in eco-friendly repellent formulations is currently a prominent research area, due to the wide diversity and high effectiveness of a number of plant-borne compounds, with special reference to essential oils (EOs) extracted from medicinal and aromatic species. Here, we reviewed current knowledge available on EOs tested as repellents against tick species of veterinary importance. Furthermore, we analysed the effectiveness of pure compounds isolated from EOs as tick repellents and their potential implications for practical use in the öreal world". A quantitative analysis of literature available is this research field was provided, along with its impact (i.e., in terms of citations over time) on the scientific community of researchers in tick control science and natural product chemistry. In the final sections, future outlooks are highlighted. We discussed major challenges to stabilize the most effective EOs and pure molecules, explore the synergistic and antagonistic effects in blends of EOs and/or pure constituents, standardize currently adopted testing methods, and evaluate non-target risks of herbal repellents.