Acaricide effect of plants from the Brazilian savanna on a population of Rhipicephalus microplus with phenotypic resistance to cypermethrin and trichlorfon.

Rhipicephalus microplus is among the most important ectoparasites for livestock. The use of synthetic acaricides has raised some concerns due to the selection of tick populations that are resistant to acaricides and environmental contamination. Therefore, plant extracts have been used as alternatives for the treatment of animals infested with ticks. In this study, R. microplus populations from seven different dairy farms were collected and assessed for their resistance to the acaricides cypermethrin or trichlorfon. Larvae of the most resistant population were used in assays to evaluate the acaricide effect of leaf extracts from plants of the Brazilian savanna. The most active extracts were also tested against fully engorged females. Among seven tick populations, five and three showed resistance level ≥ III for cypermethrin or trichlorfon, respectively. The most resistant tick population was evaluated in mortality assays with the plants Piptadenia viridiflora, Annona crassiflora, Caryocar brasiliense, Ximenia americana, and Schinopsis brasilienses. The ethanolic extracts of C. brasiliense, X. americana and S. brasilienses showed higher larvicidal effects in comparison to the other extracts and cypermethrin. The ethanolic extract of X. americana showed 60.79 % efficacy against fully engorged females of the acaricide resistant tick strain. The ethanolic extracts of C. brasiliense, X. americana, and S. brasilienses showed peaks in HPLC-DAD, indicating the presence of tannins and flavonoids. Three of the plants showed promising results and should be explored in further studies to develop novel tools to control R. microplus in cattle.

Varroa destructor mite population dynamics in africanized honeybee (Apis mellifera) colonies in a semi-arid region.

Most published data on mite infestation rates in semi-arid regions have been collected over only 3 or 4 months during a specific period of the year. Therefore, the aim of this study was to observe parasite-host dynamics of hygienic and non-hygienic Africanized bee colonies considering environmental factors that may influence Varroa destructor mite infestation rates in a semi-arid region. To this end, the brood puncture method was applied to 37 colonies, forming two groups, namely G1, encompassing 16 hygienic colonies, and G2, comprising 21 non-hygienic colonies. After forming the groups, 300 worker bees from each colony were examined monthly for mite infestations and the data were correlated with climatological records. The monthly infestation average was considered low, below 10%, except in November, when it reached 12.19% ± 6.45. No statistically significant difference was observed for inter-group infestation rates (P > 0.05). When mite infestation rates were associated with climatic variables, they were linked to colony losses (32%) due to swarming. No significant correlations between hygienic behaviour and parasite infestation rates were noted. Nonetheless, these results support the idea that there is no need to apply acaricides for V. destructor control in Brazil.

Detrimental effects of amitraz exposure in honey bees (Apis mellifera) infected with Nosema ceranae.

In recent years, there has been growing concern on the potential weakening of honey bees and their increased susceptibility to pathogens due to chronic exposure to xenobiotics. The present work aimed to study the effects on bees undergoing an infection by Nosema ceranae and being exposed to a frequently used in-hive acaricide, amitraz. To achieve this, newly emerged bees were individually infected with N. ceranae spores and/or received a sublethal concentration of amitraz in their diets under laboratory conditions. Mortality, food intake, total volume excrement, body appearance, and parasite development were registered. Bees exposed to both stressors jointly had higher mortality rates compared to bees exposed separately, with no difference in the parasite development. An increase in sugar syrup consumption was observed for all treated bees while infected bees fed with amitraz also showed a diminishment in pollen intake. These results coupled with an increase in the total number of excretion events, alterations in behavior and body surface on individuals that received amitraz could evidence the detrimental action of this molecule. To corroborate these findings under semi-field conditions, worker bees were artificially infected, marked, and released into colonies. Then, they were exposed to a commercial amitraz-based product by contact. The recovered bees showed no differences in the parasite development due to amitraz exposure. This study provides evidence to which extent a honey bee infected with N. ceranae could potentially be weakened by chronic exposure to amitraz treatment.

Exploring the effects of the acaricide cyflumetofen on the vital organs of the honey bee Apis mellifera (Hymenoptera: Apidae) workers.

Bees are important for maintaining ecosystems, pollinating crops and producing marketable products. In recent years, a decline in bee populations has been reported, with multifactorial causes, including the intensification of pesticide use in agriculture. Among pesticides, cyflumetofen is an insecticide and acaricide used in apple, coffee and citrus crops, whose main pollinator is the honey bee Apis mellifera. Therefore, this bee is a potential target of cyflumetofen during foraging. This study evaluated the histopathological and cytological damage in the midgut, hypopharyngeal glands and fat body of A. mellifera workers exposed to LC50 of cyflumetofen. The midgut epithelium of exposed bees presented cytoplasmic vacuolization, release of vesicles and cell fragments, which indicate autophagy, increased production of digestive enzymes and cell death, respectively. The cytological analysis of the midgut revealed the dilation of the basal labyrinth and the presence of spherocrystals in the digestive cells. The hypopharyngeal glands produced greater amounts of secretion in treated bees, whereas no changes were observed in the fat body. The results indicate that acute exposure to cyflumetofen negatively affect A. mellifera, causing damage to the midgut and changes in the hypopharyngeal glands, which may compromise the survival and foraging of this pollinator.

Alpha- and beta-pinene isomers act differently to control Rhipicephalus microplus (Acari: Ixodidae).

The cattle tick Rhipicephalus microplus is an ectoparasite of high importance in veterinary medicine and public health. Since synthetic chemicals used to control these ticks can select resistant strains and cause toxic effects in their hosts, there is a need to identify effective substances with fewer adverse effects. For this reason, we investigated the effects of alpha- and beta-pinene, known for their various biological effects, on the mortality and reproductive performance of R. microplus engorged female ticks. The products were diluted in a 2% Tween 80 aqueous solution. The ticks were first weighed and then immersed in the test solutions for five minutes. Then, they were dried with paper towels and fixed dorsoventrally in Petri dishes, totalling five treatment groups for each pinene and a control group treated with the solvent alone. The ticks were monitored daily for mortality, and their eggs were collected and weighed. The larval hatching rate was estimated, and the pre-oviposition and incubation periods were determined. From these data, the following parameters were calculated: egg production index, fertility rate, estimated reproduction rate, percentages of reduction in oviposition and hatching, and product efficacy. Alpha-pinene showed better results at higher concentrations, unlike beta-pinene, which was more effective at lower concentrations. The effectiveness of alpha-pinene was 74% at a concentration of 14.0 µL/mL, while beta-pinene showed 78% efficacy at 2.0 µL/mL. The results indicated for the first time different effects of two isomers in ticks, suggesting that these compounds act on R. microplus females in different ways.

Phenotypic and genotypic characterization of acaricide resistance in Rhipicephalus microplus field isolates from South Africa and Brazil.

Rhipicephalus (Boophilus) microplus is one of the most successful ticks infesting cattle around the world. This highly-invasive species transmits cattle parasites that cause cattle fever leading to a high socio-economic burden. Tick eradication programs have often failed, due to the development of acaricide resistance. Here we characterize acaricide resistance in a large number of tick isolates from regions in South Africa (KwaZulu Natal, Mpumalanga, Western & Eastern Cape provinces) and two Brazilian regions. By means of Larval Packet Tests (LPT's) acaricide resistance was evaluated against five commonly used acaricides (chlorfenvinphos, fipronil, deltamethrin, amitraz, and ivermectin). Furthermore, the coding region containing the knock down resistance (kdr) mutation, known to result in pyrethroid resistance, was sequenced. Resistance to at least one acaricide class was reported in each of the five regions, and a high proportion of tick isolates exhibited multi-resistance to at least two acaricide classes (range: 22.2-80.0%). Furthermore, resistance ratios (RR) showed high spatial variation (intercontinental, as well as regional) but low regional spatial autocorrelation. Previous and current acaricide use correlated with current RR, and several combinations of acaricide RR were positively correlated. Moreover, fipronil resistance tended to be higher in farms with more intense acaricide use. The kdr-mutations provided the ticks a fitness advantage under the selection pressure of synthetic pyrethroids based on population (kdr-allele frequency) and individual level data (genotypes). The data show the threat of acaricide (multi-)resistance is high in Brazil and South Africa, but acaricide specific levels need to be assessed locally. For this purpose, gathering complementary molecular information on mutations that underlie resistance can reduce costs and expedite necessary actions. In an era of human-caused habitat alterations, implementing molecular data-driven programs becomes essential in overcoming tick-induced socio-economic losses.

Brazil's battle against Rhipicephalus (Boophilus) microplus ticks: current strategies and future directions / A luta brasileira contra carrapatos Rhipicephalus (Boophilus) microplus: estratégias atuais e futuros caminhos

Abstract Ticks are parasitic arthropods that cause significant economic losses to livestock production worldwide. Although Rhipicephalus (Boophilus) microplus, the cattle tick, occurs throughout the Brazilian territory, there is no official program to control this tick, which is the vector of tick fever pathogens. We address the situation of R. (B.) microplus resistance to synthetic acaricides in Brazil, including cattle tick management; the status of tick resistance per Brazilian state; the history of resistance occurrence of different acaricides; multiple resistance occurrence; and the main strategies for integrated tick management. Tick control in Brazil is characterized by management errors. Local laboratories affiliated with federal and state research institutions and universities employ the Adult Immersion Test as a primary diagnostic method to assess acaricide resistance to topically applied drugs. Only three states (Acre, Amapá, and Amazonas) have no reports on resistant populations. Misinformation on tick control strategies, misuse of available products for tick control, no adoption of Integrated Parasite Management (IPM) practices, low technical support to producers, and the high-speed emergence of acaricide-resistant tick populations are the main problems. We also propose a list of needs and priorities for cattle tick control regarding communication, research, and policies.

Resumo Carrapatos são artrópodes parasitos que causam perdas econômicas significativas na produção de bovinos em todo o mundo. Embora o carrapato bovino - Rhipicephalus (Boophilus) microplus - esteja distribuído em todo o território brasileiro, não há um programa oficial de controle do parasito. Nesta revisão, foi abordada a situação da resistência de R. (B.) microplus aos carrapaticidas sintéticos no Brasil, incluindo: controle do carrapato; estado da resistência por estado; histórico da ocorrência de resistência a diferentes carrapaticidas; resistência múltipla; e as principais estratégias para o manejo integrado de carrapatos. No Brasil, laboratórios locais empregam empregam, inicialmente, o teste de imersão de adultos como método diagnóstico de resistência aos carrapaticidas. Apenas três estados (Acre, Amapá e Amazonas) não têm relatos de populações resistentes. O controle de carrapatos, no Brasil, é caracterizado por erros de manejo, há desinformação sobre estratégias de controle de carrapatos, uso inadequado dos produtos disponíveis, falta de adoção de práticas de manejo integrado de parasitos (MIP), baixo suporte técnico aos produtores e a rápida emergência de populações de carrapatos multirresistentes a carrapaticidas. Ao final, propõe-se uma lista de necessidades e prioridades para o controle de carrapatos em bovinos com relação à comunicação, pesquisa e políticas públicas.

Efficacy of either orally administered fluralaner or topically administered imidacloprid/flumethrin for controlling Rhipicephalus sanguineus sensu lato premises infestations.

BACKGROUND: Adult, nymph, and larval Rhipicephalus sanguineus sensu lato infest dogs and thrive in premises including homes and kennels. Ticks emerge from hiding to seek and attach to dogs, engorge, then leave their hosts to hide then molt or oviposit. This study evaluated the effect of either external or systemic canine treatment on R. sanguineus s.l. populations in premises. METHODS: Thirty-two dogs in eight kennels were divided into three groups; one group (eight dogs in two kennels) served as untreated controls; one group (12 dogs in three kennels) received oral fluralaner (25-56 mg/kg); and one group (12 dogs in three kennels) received topical flumethrin/imidacloprid impregnated collars. Treatments were administered once on day 0. Prior to treatment, R. sanguineus s.l. infestations were established in kennels holding dogs, by placing ticks every 2 weeks from day -84 through day -14. Kennel surfaces (walls and floors) were smooth except for uniform "hideouts" to permit precise off-host tick counting. RESULTS: Control dog kennel mean tick counts (all life stages) increased from 737 ticks/kennel at day -7 to 2213 at day 63 when all control kennel dogs were acaricide-treated as a humane endpoint. Kennels housing dogs subsequently treated with systemic fluralaner had a mean of 637 counted ticks/kennel on study day -7 (7 days before treatment). One fluralaner treatment eliminated all premises ticks (100% reduction) by day 70, and these kennels remained tick-free through study completion (day 84). Kennels housing dogs subsequently treated with an external imidacloprid/flumethrin collar had a mean of 614 counted ticks/kennel at study day -7. Collar treatment reduced counts by 90% on day 63, with kennel tick counts climbing after this and ending the study with a 75% reduction. Systemic fluralaner treatment was significantly (P = 0.003) more effective at reducing engorged adult female tick counts than external imidacloprid/flumethrin treatment. CONCLUSIONS: Fluralaner treatment eliminated off-host R. sanguineus life stages in infested kennels by day 70 following treatment and was significantly more effective than imidacloprid/flumethrin collar treatment in reducing the premises population of engorged female ticks. Imidacloprid/flumethrin treatment did not eliminate premises tick populations, with populations increasing before the study end.

Acaricidal and insecticidal activity of essential oils obtained from the aerial parts of three Mexican Bursera species.

In search of new sustainable biopesticides, we determined the phytochemical profiles, acaricidal and insecticidal properties of EOs distilled from the aerial parts of three Mexican Bursera species. Results were obtained by GC-MS analysis and three different bioassays, indicating that the EO of Bursera glabrifolia exhibited high relative abundancies of α-pinene, ß-myrcene, and α-phellandrene, as well as promising pesticidal activity against Spodoptera littoralis larvae (LD50,90 = 32.4, 107.2 µg/larva), and Musca domestica (LD50,90 = 23.2, 103.2, and 13.5, 77.4 µg/female or male adult, respectively) and Tetranychus urticae adults (LD50,90 = 7.4, 30.3 µg/cm2). The Bursera lancifolia and Bursera linanoe samples contained mainly D-limonene or linalyl acetate and linalool, respectively, and showed generally less potent pesticidal properties (S. littoralis larva, LD50,90 = 45.4, 154.4 and 52.2, 158.7 µg/larva, respectively; female M. domestica adult, LD50,90 = 69.2, 210.9 and 45.1, 243.8 µg/female adult, respectively; T. urticae adults, LD50,90 = 20.7, 90.5 and 17.5, 71.4 µg/cm2, respectively). However, the EO of B. linanoe exhibited an especially pronounced activity against male M. domestica adults (LD50,90 = 10.6, 77.2 µg/male adult). Our findings prove the pesticidal potential of Mexican Bursera species in the context of integrated pest management (IPM) and highlight the importance of conducting further research to elucidate both the active principles and possibly existing synergistic effects.

Effect of Tagetes minuta essential oil on the central nervous system of unfed Rhipicephalus sanguineus sensu lato 'tropical lineage' ticks.

Rhipicephalus sanguineus sensu lato 'tropical lineage' (Acari: Ixodidae) is considered a sanitary concern due to its role as a disease vector. Tick strains resistant to synthetic acaricides have caused difficulties in their control, besides synthetic acaricides are harmful to the environment and to the health of non-target animals. The research of plants with acaricidal and repellent properties has proved to be an efficient alternative in tick control. The genus Tagetes spp. excels for its use as traditional pest control in households and plantations and also for its potential as an acaricide against R. sanguineus under laboratory conditions. The first aim of the present study was to evaluate the effect of different doses of Tagetes minuta essential oil (TMEO) on the central nervous system (synganglion) in unfed R. sanguineus adults. The histological analysis of synganglion exposed to the different concentrations of TMEO and amitraz 12.5% (50% of the recommended dose in the package insert) showed a significant effect with signs of cell damage including volume increase, loss of shape, and vacuolization, in addition to chromatin alterations such as condensation, margination, and fragmentation. TMEO were analyzed by gas chromatography coupled with mass spectrometry showing the presence of 21 compounds that according to their chemical structure are classified as terpenoids. Among them (Z)-ß-ocimene, ocimene, (Z)-tagetone, and verbenone were found in major quantities.

Influence of the acaricide emulsion pH on the effectiveness of spray products to control the cattle tick: laboratory and field investigations.

The current work evaluated the efficacy of 10 commercial acaricides in different pHs (4.5, 5.5, and 6.5) in laboratory (adult immersion tests (AIT), pH evaluation over time) and field assays (tick counts and efficacy). In the AIT (n=70), higher efficacies were obtained when the acaricide emulsion had a more acidic pH (4.5), mainly for two combinations of pyrethroids + organophosphate (acaricide 3 and acaricide 9). For amidine, a higher pH (6.5) showed a higher efficacy. Over time, there was a trend in the pH of these emulsions increasing. When the efficacy of chlorpyrifos + cypermethrin + piperonyl butoxide (acaricide 3) at different pHs was evaluated over time (0, 6, 12, and 24h) by AIT, the less acidic pH (6.5) showed a strongly variation in the acaricide efficacy range. The mean pH of the water samples from different regions of Brazil was 6.5. In the field, the association of pyrethroid + organophosphates (acaricide 9) with pH of 4.5 and 5.5 were more effective in tick control than the emulsion prepared with this same spray formulation at pH 6.5. The pH of the acaricide emulsions is an important point of attention and is recommended that the veterinary industry start to develop/share information regarding how the pH can affect the acaricide efficacy.

Toxic effect of Callistemon viminalis essential oil on the ovary of engorged Rhipicephalus microplus female ticks (Acari: Ixodidae).

Rhipicephalus microplus is the main ectoparasite of cattle and its parasitism can reduce weight gain of hosts, in addition to causing anemia, increasing the risk of myiasis, and resulting in the transmission of Babesia bovis and Anaplasma marginale, among other pathogens. The use of synthetic chemicals plays an important role in controlling these ticks. However, its frequent and indiscriminate use has contributed to the selection of resistant strains, resulting in greater interest in the search for natural-origin products. The shrub Callistemon viminalis (Myrtaceae), also known as weeping bottlebrush, is known for its antibacterial, acaricidal, repellent, and antifungal activities, but there are no reports in the literature about its effects on the internal morphology of ticks. This study aimed to extract and characterize the essential oil obtained from the leaves of C. viminalis. Additionally, its effects on the ovary morphology of engorged R. microplus were assessed through histological, histochemical, and morphometric techniques. Exposure to C. viminalis caused dose-dependent morphological changes, such as cellular alterations in the epithelial layer lining the ovary lumen and the pedicel, irregularity of the chorion and oocyte shape, changes in protein and carbohydrate content, decrease in oocyte size, reduction in the size of the nucleus as well as cytoplasmic and nucleolar vacuolation. Thus, C. viminalis essential oil exhibited a toxic effect on the reproductive system of R. microplus, which may result in the reproductive impairment of this tick species.

Essential oil Ageratum conyzoides chemotypes and anti-tick activities.

Rhipicephalus (Boophilus) microplus represents a significant obstacle to animal productivity in tropical and subtropical areas, leading to considerable economic losses for the dairy and meat production industries. Essential oils (EO) extracted from Ageratum conyzoides are known to cause death and induce morphogenetic abnormalities in several insect species. This plant, however, presents morphological flower variations, which range from white to purple, associated to different chemotypes. In this context, this study aimed to conduct a novel assessment on the effects of EO extracted from two A. conyzoides chemotypes in the control of the bovine tick R. microplus. The primary constituents of the oil obtained from white flower samples (WFs) were precocene I (80.4 %) and (E)-caryophyllene (14.8 %), while purple flower oil samples (PFs) contained predominantly ß-acoradiene (12.9 %), γ-amorphene (12.3 %), α-pinene (9.9 %), bicyclogermacrene (8.9 %), α-santalene (8.7 %), and andro encecalinol (5.6 %). Interestingly, only the EO chemotype from A. conyzoides PFs displayed acaricidal activity towards R. microplus larvae, with an LC50 of 1.49 mg/mL.

Evaluation of the interaction of citral, geraniol and thymol on the poultry red mite Dermanyssus gallinae (DE GEER, 1778) under in vitro conditions / Avaliação da interação de citral, geraniol e timol no ácaro-vermelho-das-aves Dermanyssus gallinae(DE GEER, 1778) em condições in vitro

The control of Dermanyssus gallinaein small productions of laying hens is carried out by using chemical methods. However, its indiscriminate use has generated resistance and environmental pollution problems. This problem has encouraged the use of natural substances to control mites. Thus, the objective of this work was to evaluate the acaricidal activity of the bioactivecitral (Ci), geraniol (Ge) and thymol (Thy) on D. gallinae under in vitro conditions using six concentrations (0.05, 1, 2, 3, 4 and 5g/mL). In addition, the interactions of the mixtures of the three bioactive were evaluated through binary (1:1) and tertiary (1:1:1) combinations. The interaction between of the combination of bioactive was performed by using CompuSyn software and calculating the combination index (CI). LC50, LC90, and LC99with 95% confidence limits were estimated by Probit analysis. The bioactive Ci, Ge and Thy showacaricidal activity on the poultry red mite. The combination of Ge:Thy and Ci:Ge showed very strong synergism with CI of 0.084 and 0.052, whereas Ci:Thy showed strong synergism with CI of 0.122 at a concentration of 0.05g/mL. Thetertiary combination in 1:1:1 showed a higher toxic effect and strong synergistic effects at low concentrations with 100% mortality at 1g/mL concentration with a CI of 0.147. The combination of natural bioactive could be an additional way to control D. gallinae without putting thewelfare of the birds at risk and would be an environmentally friendly measure.(AU)

O controle de Dermanyssus gallinaeem pequenas produções de poedeiras é realizado por métodos químicos.No entanto, seu uso indiscriminado tem gerado problemas de resistência e poluição ambiental. Este problema tem incentivado o uso de substâncias naturais para o controle de ácaros. Assim, o objetivo deste trabalho foi avaliar a atividade acaricida dos bioativos citral (Ci), geraniol (Ge) e timol (Thy) sobre D. gallinaeem condições in vitro utilizando seis concentrações (0,05, 1, 2, 3, 4 e 5g/mL). Além disso, as interações das misturas dos três bioativos foram avaliadas por meio decombinações binárias (1:1) e terciárias (1:1:1). O sinergismo da combinação dos bioativos foi realizado utilizando o software CompuSyn e calculando o índice de combinação (CI). LC50, LC90e LC99com limites de confiança de 95% foram estimados por análise Probit. Os bioativos Ci, Ge e Thy apresentam atividade acaricida sobre o ácaro-vermelho-da-aves. A combinação de Ge:Thy e Ci:Ge apresentou sinergismo muito forte com CI de 0,084 e 0,052, enquanto Ci:Thy apresentou forte sinergismo com CI de 0,122 na concentração de 0,05g/mL. A combinação terciária em 1:1:1 apresentou maior efeito tóxico e fortes efeitos sinérgicos em baixas concentrações com 100% de mortalidade em concentração de 1g/mL com CI de 0,147. A combinação de bioativos naturais poderia ser uma forma adicional de controle deD. gallinaesem colocar em risco o bem-estar das aves e seria uma medida ecologicamente correta.(AU)

Acaricides containing zein nanoparticles: A tool for a lower impact control of the cattle tick Rhipicephalus microplus.

Nanoformulations containing zein nanoparticles (ZN) can promote the stability and protection of molecules with acaricidal activity. The present study sought to develop nanoformulations with ZN associated with cypermethrin (CYPE) + chlorpyrifos (CHLO) + a plant compound (citral, menthol or limonene), characterize them, and verify their efficacy against Rhipicephalus microplus ticks. Additionally, we aimed to assess its safety in nontarget nematodes found in soil at a site subjected to contamination by acaricides. The nanoformulations were characterized by dynamic light scattering and nanoparticle tracking analysis. Nanoformulations 1 (ZN+CYPE+CHLO+citral), 2 (ZN+CYPE+CHLO+menthol), and 3 (ZN+CYPE+CHLO+limonene) were measured for diameter, polydispersion, zeta potential, concentration, and encapsulation efficiency. Nanoformulations 1, 2, and 3 were evaluated in a range from 0.004 to 0.466 mg/mL on R. microplus larvae and caused mortality > 80% at concentrations above 0.029 mg/mL. The commercial acaricide Colosso® (CYPE 15 g + CHLO 25 g + citronellal 1 g) was evaluated also from 0.004 to 0.512 mg/mL and resulted in 71.9% larval mortality at 0.064 mg/mL. Formulations 1, 2, and 3 at 0.466 mg/mL showed acaricidal efficacy of 50.2%, 40.5%, and 60.1% on engorged females, respectively, while Colosso® at 0.512 mg/mL obtained only 39.4%. The nanoformulations exhibited long residual period of activity and lower toxicity to nontarget nematodes. ZN was able to protect the active compounds against degradation during the storage period. Thus, ZN can be an alternative for the development of new acaricidal formulations using lower concentrations of active compounds.

Complete genome sequence dataset of enthomopathogenic Aspergillus flavus isolated from a natural infection of the cattle-tick Rhipicephalus microplus.

As the most important bovine ectoparasite, the southern cattle tick Rhipicephalus microplus transmits lethal cattle diseases such as babesiosis and anaplasmosis, costing the global livestock industry billions of dollars annually. To control cattle ticks, preventive treatment of cattle with pesticides is a common practice; however, after decades of chemical treatment, pesticide resistance has arisen in cattle ticks, rendering most formulations ineffective over time. Facing the perspective of running out of effective chemical treatments against R. microplus, research on biocontrol alternatives is necessary. Acaro-pathogenic microorganisms isolated from different developmental stages of R. microplus offer potential as biocontrol agents. Aspergillus flavus strain INIFAP-2021, isolated from naturally infected cattle ticks, produced high levels of mobility and mortality in the tick population during experimental infections. The whole genome of the fungi was sequenced using the DNBSEQ platform by BGI. The genome was assembled using SOAPaligner, and A. flavus NRRL3357 was used as the reference genome; the complete genome contained eight pairs of chromosomes and 36.9 Mb with a GC content of 48.03%, exhibiting 11482 protein-coding genes. The final genome assembly was deposited at GenBank as a bio project under accession number PRJNA758689, and supplementary material is accessible through Mendeley DOI: 10.17632/mt8yxch6mz.1.

Field efficacy of Metarhizium anisopliae oil formulations against Rhipicephalus microplus ticks using a cattle spray race.

Rhipicephalus microplus tick is the main ectoparasite of cattle in Brazil. The exhaustive use of chemical acaricides to control this tick has favored the selection of resistant tick populations. Entomopathogenic fungi, as Metarhizium anisopliae, has been described as a potential biocontroller of ticks. Therefore, the aim of this study was to evaluate the in vivo efficacy of two oil based formulations of M. anisopliae for the control of the cattle tick R. microplus under field conditions using a cattle spray race as a method of treatment. Initially, in vitro assays were carried out with an aqueous suspension of M. anisopliae, using mineral oil and/or silicon oil. A potential synergism between oils and fungus conidia for tick control was demonstrated. Additionally, the usefulness of silicon oil in order to reduce mineral oil concentration, while improving formulation efficacy was illustrated. Based on the in vitro results, two formulations were selected for use in the field trial: MaO1 (107 conidia/mL plus 5% mineral oil) and MaO2 (107 conidia/mL plus 2.5% mineral oil and 0.01% silicon oil). The adjuvants concentrations (mineral and silicon oils) were chosen since preliminary data indicate that higher concentrations caused significant mortality in adult ticks. For this, 30 naturally infested heifers were divided into three groups based on previous tick counts. The control group did not receive treatment. The selected formulations were applied on animals using a cattle spray race. Subsequently, tick load was evaluated weekly by counting. The MaO1 treatment significantly reduced the tick count only on day +21, reaching approximately 55% efficacy. On the other hand, MaO2 showed significantly lower tick counts on days +7, +14, and +21 after treatment, with weekly efficacy achieving 66%. The results showed a substantial reduction of tick infestation, up to day +28, using a novel formulation of M. anisopliae based in the mixture of two oils. Moreover, we have shown, for the first time, the feasibility of employing formulations of M. anisopliae for large-scale treatment methods, such as a cattle spray race, which in turn, may increase the use and adhesion to biological control tools among farmers.

Putative target sites in synganglion for novel ixodid tick control strategies.

Acaricide resistance is a global problem that has impacts worldwide. Tick populations with broad resistance to all commercially available acaricides have been reported. Since resistance selection in ticks and their role in pathogen transmission to animals and humans result in important economic and public health burden, it is essential to develop new strategies for their control (i.e., novel chemical compounds, vaccines, biological control). The synganglion is the tick central nervous system and it is responsible for synthesizing and releasing signaling molecules with different physiological functions. Synganglion proteins are the targets of the majority of available acaricides. In this review we provide an overview of the mode-of-action and resistance mechanisms against neurotoxic acaricides in ticks, as well as putative target sites in synganglion, as a supporting tool to identify new target proteins and to develop new strategies for tick control.

Efficacy of essential oils of Egletes viscosa and Lippia schaueriana on the reproductive biology of Rhipicephalus sanguineus sensu lato engorged females.

The study analyzed the chemical composition and the acaricide effect of Egletes viscosa Less (macela-da-terra) and Lippia schaueriana Mart. (lipia-da-serra) essential oils (EOs) on Rhipicephalus sanguineus s. l. (Acari: Ixodidae) engorged females. The chemical analysis (GC-MS and GC-FID) identified 27 components in E. viscosa EO and 18 in L. schaueriana EO, which comprise more than 98% of its constituents. The effects of the oils on the reproductive biology of R. sanguineus ticks were assessed by adult immersion test. Both EOs significantly reduced (p < 0.05) the egg production index when the females were exposed to 25 and 50 mg/mL, also affecting the egg viability. During the laying process, the eggs produced by the females exposed to the EO showed several morphological alterations such as dehydrated, darkened, and disaggregated, and these alterations were more severe as the concentrations increased. The mortality percentages were 58.9%, 70.8% and 92.7% when the ticks were exposed to 12.5, 25 and 50 mg/mL of E. viscosa oil, respectively. In the same concentrations, the efficacy of L. schaueriana was 39.3%, 53.4%, and 84.6%. Therefore, it can be concluded that the essential oils of E. viscosa and L. schaueriana have acaricidal effect in females of R. sanguineus s.l ticks.

Mechanisms of acaricide resistance in ticks

Background: In several countries, including Brazil, the livestock industry plays a key role in the country's economy. Brazil has the second largest bovine herd in the world and the biggest commercial herd. Ticks are an ongoing problem for both large operation cattle producers and small family farmers. Rhipicephalus microplus causes expressive losses in cattle breeding, since it occurs in important beef production zones like South America, Africa, and Oceania. Some of the negative consequences of tick infestation to cattle breeding are anemia, loss in milk and beef production, and transmission of Babesia bovis and B. bigemina. Significant losses are caused by the cattle tick (R. microplus) in several regions of the world, costing around US$ 3.3 billion per year to the Brazilian livestock industry alone. The tick control methods are mainly based on synthetic acaricides. However, the improvement of current tick control requires the identification of new molecular targets in tick physiology and development of molecule compounds to target important physiology pathways. The strategies proposed to address this issue are expand the knowledge about the molecules involved in the detoxification of chemicals to enhance the efficacy of the acaricides as well as to develop new compounds for chemical control. Review: Tick control is currently based on chemical acaricides; however, effective control and prevention of tick infestation remain distant goals. In recent decades, a progressive decrease in the efficiency of acaricides due to drug resistance has been observed. Acaricide resistance is an evolutionary adaptation, which implies the existence of behavioral and physiological mechanisms that allow the survival of resistant individuals. Four resistance mechanisms are described: behavioral resistance, reduced drug penetration, target site insensitivity and increased drug detoxification. Augmented drug detoxification may be due to increased activity of enzymes or transporters due to increased gene expression or mutations in some genes. Research focus on mechanisms of acaricide resistance in ticks characterized detoxification pathways based on (1) increased activity of enzymes (cytochrome p450, esterase and GST) which play a role in biochemically altering acaricides towards decreased toxicity and, (2) enhanced excretion of the modified less toxic compounds. To bypass the current problems, a better understanding of the biology, physiology, and molecular biology of the mechanisms of resistance to acaricides is fundamental to prolong their efficiency in controlling ticks. Moreover, identifying the genes and proteins associated with resistance can support in the development of more sensitive diagnostic methods to identify acaricide resistance, as well as improving control strategies. Discussion: In the last years, many researchers have been studying resistance mechanisms and important advances have been made which showed that, in several tick species, ABC transporters, esterases, P-450 cytochromes and glutathione-S-transferases participate in acaricide resistance. The characterization of the alterations in the targets in tick physiology and identification of new drugs with potential to tick control are crucial goals to increase tick control