Strategic control of the cattle tick Rhipicephlaus microplus applied to rotational and silvopastoral grazing systems in subtropical areas.

This work evaluated if strategic control based on no more than three or four annual treatments is useful to control Rhipicephalus microplus infestations on cattle when it is applied to intensive rotational grazing and silvopastoral systems with high stocking rates in subtropical areas. In the intensive rotational grazing system, three annual treatments with chemical acaricides were applied on cattle in two different schemes: between spring and early summer and from late winter and late spring. Strategic control based on three treatments with chemical acaricides from late winter to late spring plus an additional fourth treatment in summer was tested in the silvopastoral system. In the intensive rotational grazing systems, the control schemes allow to reach a significant reduction in the tick load on cattle considering a time interval from spring to autumn. However, the efficacy levels were not high enough in some specific moments, namely, the tick counts of summer and autumn (there were not significant differences between treated and control groups). The scheme evaluated in the silvopastoral grazing system yielded better results than those tested for the intensive rotational system, because significant differences in tick load between treated and control groups were observed in all post-treatment counts and when the analysis was performed for the whole study period. However, values of efficacy in the count-by-count comparison were disparate, ranging from 64.1 to 99.7. Although the efficacy values obtained in the silvopastoral system were better than those of the rotational grazing systems, the total tick load on treated cattle in autumn was not low enough (mean abundance values 25.14 and 38.14). Ticks were more evenly distributed among hosts in late summer and autumn than in spring or early summer, where few hosts carry most of the ticks. Some management strategies as intensive rotational systems or silvopastoral structures can lead to a more efficient forage use, but they imply greater tick challenge than in extensive grazing systems. In these situations, the schemes of strategic control bases on three or four annual treatments should be complemented with additional tactical treatments in late summer or autumn.

Repellent activity of the non-host semiochemical (E)-2-octenal against Amblyomma sculptum and Amblyomma dubitatum ticks under field conditions.

Amblyomma ticks pose a significant public health threat due to their potential to transmit pathogens associated with rickettsial diseases. (E)-2-octenal, a compound found in donkeys (Equus asinus), exhibits strong repellent properties against Amblyomma sculptum nymphs under laboratory conditions. This study assessed the effectiveness of the (E)-2-octenal in wearable slow-release devices for personal human protection against Amblyomma ticks under natural conditions. Slow-release devices treated with (E)-2-octenal and untreated controls were prepared and tested on two volunteers walking through a tick-infested area in Goiania, Brazil. The experiment was conducted twice daily for three series of 10 days, with each volunteer wearing two devices attached to each leg, one on the ankle and one just above the thigh. Volunteers with control and treated devices exchanged them between rounds. Also, the daily release rate of (E)-2-octenal from the slow-release devices was determined in the laboratory, increasing significantly from 0.77 ± 0.14 µg/day on the first day to 9.93 ± 1.92 µg/day on the 4th day and remaining constant until the 16th day. A total of 5409 ticks were collected from both volunteers. Treated devices resulted in recovering fewer ticks (n = 1,666; 31%) compared to untreated devices (control: n = 3,743; 69%). (E)-2-octenal effectively repelled Amblyomma spp. larvae, A. sculptum adults, and exhibited pronounced repellency against A. dubitatum nymphs and adults. These findings suggest the potential of (E)-2-octenal delivered by wearable slow-release devices as a green-based repellent. Further improvements, however, are necessary to provide better protection for humans against A. sculptum and A. dubitatum in field conditions.

What is the optimal timing to initiate strategic control of Rhipicephalus microplus in taurine cattle in a tropical region?

Cattle tick control poses a significant challenge for livestock in tropical and subtropical regions. The objective of this study was to determine the most suitable timing to initiate a strategic tick control program and to identify the ideal number of acaricide treatments for adult taurine cattle (Bos taurus taurus) in a tropical region throughout the year. Three groups with 10 bovines each were performed: T01 (strategic treatment in late autumn/winter/late spring, every 28 days), T02 (strategic treatment to act in the "first tick generation" - early spring/summer/early autumn, every 28 days) and T03 (control). Tick counts (females 4-8 mm) were conducted every 14 days. If the tick burden in any group reached 30 or more during these counts, we applied an additional treatment. Over the course of a year, T02 required significantly fewer (p < 0.05) acaricide treatments than T01, with nine treatments for T02 and eleven for T01. Furthermore, during the tick counts, animals in T02 showed a lower tick burden compared to those in T01. Initiating the strategic tick control program in early spring, corresponding to the first tick generation, proved more effective than starting in autumn. This approach not only required fewer acaricide treatments but also resulted in a reduced tick burden. These benefits are particularly valuable in terms of animal welfare and managing acaricide resistance issues.

Stochastic modelling to predict a priori the potential outcomes of different control schemes against the cattle tick Rhipicephalus microplus.

Stochastic models are valuable tools to describe and analyze tick population dynamic in a given area, and to evaluate different control schemes. The objective of this study was to provide a tool to predict a priori how a control scheme could affect the abundance of Rhipicephalus microplus in an area highly favourable for its development, through the building of a stochastic model of the population dynamic of this tick. The dynamic was stochastically modelled using field data of the parasitic and non-parasitic phases of R. microplus. The host susceptibility to tick infestations was also considered by including representative values of natural resistance of three different breeds (Bos indicus, B. taurus and B. indicus x B. taurus). Two different control schemes (strategic and threshold methods) using three annual applications of synthetic acaricides in different moments were evaluated. Furthermore, we have evaluated the impact of different moments of pasture spelling as a tool for tick control on the dynamic of the non-parasitic phases of R. microplus. The results showed that the model appropriately fits to field data and can simulate the annual variability in female ticks count in animals from different ecological characteristics. The model has also captured the variability that host susceptibility has on tick abundance. This fact was expressed in the different levels of tick abundance obtained for the three breeds of bovines. According to the model, strategic control applications of chemical acaricides have more efficacy than the threshold control method. The model indicates that a pasture spelling started in early or mid-summer generates a higher reduction in the number of available eggs in pastures. Analysis of the results allows to conclude that the model developed in this study was useful to predict a priori the performance of different control methods based on the strategic application of chemical acaricides or by applying pasture spelling.

Essential oils and isolated compounds for tick control: advances beyond the laboratory.

BACKGROUND: Tick control is a worldwide challenge due to its resistance to acaricides. Essential oils (EOs) and isolated compounds (EOCs) are potential alternatives for tick control technologies. METHODS: A review with EOs and EOCs, under field and semi-field conditions, was performed based on Scopus, Web of Science and PubMed databases. Thirty-one studies published between 1991 and 2022 were selected. The search was performed using the following keywords: "essential oil" combined with "tick," "Ixodes," "Argas," "Rhipicephalus," "Amblyomma," "Hyalomma," "Dermacentor," "Haemaphysalis" and "Ornithodoros." The words "essential oil" and "tick" were searched in the singular and plural. RESULTS: The number of studies increased over the years. Brazil stands out with the largest number (51.6%) of publications. The most studied tick species were Rhipicephalus microplus (48.4%), Ixodes scapularis (19.4%), Amblyomma americanum and R. sanguineus sensu lato (9.7% each). Cattle (70%) and dogs (13%) were the main target animal species. Regarding the application of EOs/EOCs formulations, 74% of the studies were conducted with topical application (spray, pour-on, foam, drop) and 26% with environmental treatment (spray). Efficacy results are difficult to evaluate because of the lack of information on the methodology and standardization. The nanotechnology and combination with synthetic acaricides were reported as an alternative to enhance the efficacy of EOs/EOCs. No adverse reactions were observed in 86.6% of the studies evaluating EOs/EOCs clinical safety. Studies regarding toxicity in non-target species and residues are scarce. CONCLUSIONS: This article provides a comprehensive review on the use of EOs and EOCs to reduce tick infestations, in both the hosts and the environment. As future directions, we recommend the chemical characterization of EOs, methodology standardization, combination of EOs/EOCs with potential synergists, nanotechnology for new formulations and safety studies for target and non-target organisms, also considering the environmental friendliness.

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.

Usos de la levadura Pichia pastoris en la producción de proteínas recombinantes / Uses of Pichia pastoris yeast in the production of recombinant proteins

La levadura metilotrófica Pichia pastoris (clasificada actualmente como Komagataella phaffii) es una de las más importantes para la producción de proteínas heterólogas. En el trabajo se presenta un análisis de las principales características que se ponen de manifiesto en la expresión de proteínas recombinantes expresadas en este microorganismo. Se describen las cepas disponibles para la transformación y producción de proteínas recombinantes expresadas en Pichia pastoris, los principales vectores comerciales para la expresión, los promotores más eficientes, los marcadores seleccionables, la señal de secreción, los métodos usados en las transformaciones genéticas y los patrones de glicosilación que se presentan. Se brindan recomendaciones generales acerca de los parámetros de bioprocesos como la composición del medio, el pH, la temperatura, la velocidad de aireación, la inducción y las estrategias de alimentación para alcanzar altos valores de productividad. Se presentan los resultados de las aplicaciones de Pichia pastoris en la producción de dos vacunas en Cuba, la vacuna contra la hepatitis B y la vacuna para el control de la garrapata(AU)

Pichia pastoris metylotrofic yeast (currently classified as Komagataella phaffii) is one of the most important yeast for the production of heterologous proteins. The work presents an analysis of the main characteristics that are marked in the production of recombinant proteins expressed in Pichia pastoris. It describes the strains available for the transformation and production of recombinant proteins expressed in P. pastoris, the main commercial vectors for expression, the most efficient promoters, selectable markers, the secretion signal, the methods used in genetic transformations and glycosylation patterns that occur. General recommendations are provided on bioprocess parameters such as media composition, pH, temperature, aeration velocity, induction, and feeding strategies to achieve high productivity values. The results of Pichia pastoris applications for the production of two vaccines in Cuba, the hepatitis B vaccine and the tick control vaccine are shown(AU)

Assessment of weight gain and control of parasitism by Rhipicephalus microplus in dairy cattle in the field using organosynthetic parasiticide, phytotherapics and homeopathy / Avaliação do ganho de peso e controle do parasitismo por Rhipicephalus microplus em bovinos leiteiros a campo usando parasiticida organosintético, fitoterápicos e homeopatia

The goal of this research was to compare the effect of the following products on dairy cattle, parasitized by Rhipicephalus microplus: organosynthetics - Clorfenvinfós and Ivermectina (OG); phytotherapics - Eucalyptus oil (EG) and Neem cake (NG); Homeopathy (HG); The control group (CG) received no treatment. Infestation was by R. microplus (MIC) and weight gain (GP) were evaluated. The study included 60 animals (5 groups) from ­ Dutch / Zebu, aged between 25-44 months and initial weight between 211-477kg. EG and NG showed MIC 84.9% and 14.0% greater than CG, respectively (P <0.05; P = 0). HG and OG had MIC less than CG 24.4% and 16.9%, respectively (P<0.05; P <0.05). EG, NG and OG obtained GP lower than CG in 7.9%, 8.9% and 8.06% (P <0.05) respectively. The HG GP was 4.9% higher (P <0.05) than CG. This was the first research to prove parasitism control by R. microplus in a field test, using homeopathy. The methodology for choosing Homeopathy for the control of enzooties, developed and tested for the first time in this study, proved to be adequate and efficient, opening the possibility for establishing a new methodology for strategic control of parasitism by R. microplus.(AU)

O objetivo desta pesquisa foi comparar o efeito dos seguintes produtos sobre bovinos leiteiros, parasitados por Rhipicephalus microplus: organossintéticos - clorfenvinfós e ivermectina (OG); fitoterápicos - óleo de eucalipto (EG) e torta de Neem (NG) e homeopatia (HG). O grupo controle (CG) não recebeu tratamento. Foram avaliados infestação por R. microplus (MIC) e ganho de peso/grupo (GP) em 60 animais (5 grupos), a partir de ­ holandês/zebu, com idade entre 25 e 44 meses e peso inicial entre 211 e 477kg. EG e NG apresentaram MIC 84,9% e 14,0% maior que CG, respectivamente (P<0,05; P=0). HG e OG apresentaram MIC menor que CG 24,4% e 16,9%, respectivamente (P<0,05; P<0,05). EG, NG e OG obtiveram GP menor que CG em 7,9%, 8,9% e 8,06% (P<0,05), respectivamente. O GP do HG foi 4,9% maior (P<0,05) que o CG. Esta foi a primeira pesquisa a comprovar controle do parasitismo por R. microplus em teste a campo, usando homeopatia. A metodologia para escolha de medicamentos homeopáticos para controle de enzootias, desenvolvida e testada pela primeira vez neste estudo, mostrou-se adequada e eficiente, abrindo a possibilidade para estabelecimento de nova metodologia para controle estratégico do parasitismo por R. microplus.(AU)

Interfering with cholesterol metabolism impairs tick embryo development and turns eggs susceptible to bacterial colonization.

Cholesterol is a known precursor of arthropod molecules such as the hormone 20-hydroxyecdysone and the antimicrobial boophiline, a component of tick egg wax coat. Because the cholesterol biosynthetic pathway is absent in ticks, it is necessarily obtained from the blood meal, in a still poorly understood process. In contrast, dietary cholesterol absorption is better studied in insects, and many proteins are involved in its metabolism, including Niemann-Pick C (NPC) transporter and acyl-CoA:cholesterol acyltransferase (ACAT), as well as enzymes to convert between free cholesterol and esterified cholesterol. The present work addresses the hypothesis that tick viability can be impaired by interfering with cholesterol metabolism, proposing this route as a target for novel tick control methods. Two drugs, ezetimibe (NPC inhibitor) and avasimibe (ACAT inhibitor) were added to calf blood and used to artificially feed Rhipicephalus microplus females. Results show that, after ingesting avasimibe, tick reproductive ability and egg development are impaired. Also, eggs laid by females fed with avasimibe did not hatch and were susceptible to Pseudomonas aeruginosa adhesion and biofilm formation in their surfaces. The immunoprotective potential of ACAT against ticks was also accessed using two selected ACAT peptides. Antibodies against these peptides were used to artificially feed female ticks, but no deleterious effects were observed. Taken together, data presented here support the hypothesis that enzymes and other proteins involved in cholesterol metabolism are suitable as targets for tick control methods.

Repellent activity of acetylcarvacrol and its effects on salivary gland morphology in unfed Rhipicephalus sanguineus sensu lato ticks (Acari: Ixodidae).

Rhipicephalus sanguineus sensu lato (s.l.), commonly known as brown dog tick, is a widely distributed tick species that is substantially important for human and veterinary medicine. Therefore, it is the target of different control methods. Carvacrol and its semisynthetic derivative, acetylcarvacrol, are promising chemical compounds for alternative tick control. Thus, this study aimed to compare the repellent activities of carvacrol and acetylcarvacrol at different concentrations and drying times. Additionally, morphological alterations found in salivary glands were evaluated through histological techniques after exposure to acetylcarvacrol. The impact of the morphological changes on the development and survival of acini/cells in salivary glands was measured by a semiquantitative analysis. The repellent action of both compounds did not differ when evaluated at different concentrations, although acetylcarvacrol increased its effects as the concentration raised. Regarding the different drying times, acetylcarvacrol maintained its effects after 3 hours of exposure, while the efficacy of carvacrol decreased during this time period. Salivary glands of unfed R. sanguineus s.l. females showed dose-dependent alterations in the size and shape of acini as well as cytoplasmic vacuolization. Loss of the acinar cell limit, rupture of secretory granules and nuclear changes in the cells were also observed in the treated groups. Thus, our results demonstrated the potential of acetylcarvacrol to act as repellent against R. sanguineus s.l. Additionally, the morphological alterations found in salivary glands may interfere with the feeding process of ticks, which contributes to mitigate infestation by this species.

Evaluation of different strategic control protocols for Rhipicephalus microplus on cattle according to tick burden.

The development of a strategic protocol is fundamental to the control of Rhipicephalus microplus. The efficacy of different strategic tick control protocols (Day 1 to Day 119) using commercial acaricides according to R. microplus burden on bovines was evaluated. Female ticks (4.5-8 mm in length) were initially counted on cattle to form four groups of bovines with low and high tick burdens (treated and control), with 10 animals each. The animals were then (Day 0) kept in different paddocks, and the bovines from the two treated groups received their first treatment. The main difference in the protocols was the use of a spray formulation on animals with high tick burden. Additionally, the criterion for animal re-treatment (treatment interval) during the proposed strategic protocol was evaluated according to tick length by visual inspection - if 30% of the bovines of a group presented ticks < 4 mm between their legs and dewlap, the treatment was applied, which could change the originally proposed intervals. The number of days for which animals from the treated groups remained without acaricide administration (palliative control, ≥30 tick females < 4 mm) after the end of the strategic tick control protocol was recorded. Tick counts and visual inspection were done weekly until days 203 and 119, respectively. The results showed that the adopted protocol was successful based on calculated efficacy. Mean efficacies from Day 7 to Day 119 were 86.1% and 96.1% for treated groups with low and high tick burdens, respectively, and mean tick count did not differ between them (P > 0.05) but did differ from their respectively controls (P = <0.0001). The use of spray formulation at the beginning of the protocol for animals with a high tick burden helped to avoid harmful tick infestations. Visual analysis of tick length anticipated the proposed treatment intervals. Treated groups remained without palliative treatment for 70 days, while control groups needed treatment every 28 days. It was concluded that strategic control protocols must be developed according to tick burden, and tick length can be used to indicate when treatment needs to be applied.

Simulated dynamics of southern cattle fever ticks (Rhipicephalus (Boophilus) microplus) in south Texas, USA: investigating potential wildlife-mediated impacts on eradication efforts.

BACKGROUND: Cattle fever ticks (CFT), Rhipicephalus (Boophilus) annulatus and R. (B.) microplus, are vectors of microbes causing bovine babesiosis and pose a threat to the economic viability of the US livestock industry. Efforts by the Cattle Fever Tick Eradication Program (CFTEP) along the US-Mexico border in south Texas are complicated by the involvement of alternate hosts, including white-tailed deer (Odocoileus virginianus) and nilgai (Boselaphus tragocamelus). METHODS: In the present study, we use a spatially explicit, individual-based model to explore the potential effects of host species composition and host habitat use patterns on southern cattle fever ticks (SCFT, R. (B.) microplus) infestation dynamics and efficacy of eradication schemes. RESULTS: In simulations without eradication efforts, mean off-host larval densities were much higher when cattle were present than when only white-tailed deer and nilgai were present. Densities in mesquite and meadows were slightly higher, and densities in mixed brush were much lower, than landscape-level densities in each of these scenarios. In eradication simulations, reductions in mean off-host larval densities at the landscape level were much smaller when acaricide was applied to cattle only, or to cattle and white-tailed deer, than when applied to cattle and nilgai. Relative density reductions in mesquite, mixed brush, and meadows depended on host habitat use preferences. Shifting nilgai habitat use preferences increasingly toward mixed brush and away from mesquite did not change mean off-host larval tick densities noticeably at the landscape level. However, mean densities were increased markedly in mesquite and decreased markedly in mixed brush, while no noticeable change in density was observed in meadows. CONCLUSIONS: Our results suggest that continued integration of field data into spatially explicit, individual-based models will facilitate the development of novel eradication strategies and will allow near-real-time infestation forecasts as an aid in anticipating and preventing wildlife-mediated impacts on SCFT eradication efforts.

Barriers to Effective Tick Management and Tick-Bite Prevention in the United States (Acari: Ixodidae).

Lyme and other tick-borne diseases are increasing in the United States. Development of tick control tools have focused primarily on the blacklegged tick, Ixodes scapularis Say. Application of acaricides or entomopathogenic fungal agents to kill host-seeking ticks or ticks on rodents can suppress I. scapularis abundance in residential landscapes, but evidence is lacking for impact on human tick bites or tick-borne disease. Similar studies remain limited for the lone star tick, Amblyomma americanum (L.). Other knowledge gaps include how well homeowners and pest control companies perform in the broadcast application of tick-killing products, relative to high efficacy reported in research studies, and the tick-killing potential of natural product formulations exempt from Environmental Protection Agency registration. Area-wide control based on preventing ticks from feeding on their main reproductive host, the white-tailed deer, can suppress populations of both I. scapularis and A. americanum. Some studies also suggest an impact on Lyme disease cases, but this needs to be further validated in larger-scale intervention studies. The effectiveness, scale, cost, and implementation of various tick management strategies are important considerations in efforts to reduce human tick encounters and tick-borne disease. Additional barriers include weak incentives for industry and academia to develop, test, and register new tick and pathogen control technologies, including vaccines targeting humans, tick reproductive hosts, or wildlife pathogen reservoirs. Solutions will need to be 'two-pronged': improving the tick and pathogen control toolbox and strengthening the public health workforce engaging in tick control at local and state levels.

Morphophysiological analysis of the salivary glands of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) exposed to ozonated water: A control strategy.

The tick Rhipicephalus sanguineus sensu lato has great medical and veterinary importance, mainly because the ability to transmit many diseases, causing harm to pets but also risks to public health. The blood spoliation and transmission of pathogens occur because of the immunosuppressive action of these ticks' saliva, a potent mixture of bioactive substances that is secreted by the salivary glands, one of the organs responsible for their biological success, and hence the target of studies for their control. Ozone has promise for use as an alternative acaricide, due to its proven efficiency in controlling agricultural and food pests, besides posing no risk of environmental contamination or to animal and human health. Therefore, this study evaluated the acaricidal potential of exposure of females of R. sanguineus s.l. to ozonated water at many concentrations and analysed the morphophysiological alterations of the salivary glands, employing histological and light microscopic techniques. The results demonstrated that the ozonated water at the concentrations investigated caused severe alterations in the salivary glands, bringing a new perspective for control of R. sanguineus s.l., through an ecologically correct method due to the absence of harm to non-target organisms and the environment.

In vitro efficacy of two commercial products of Metarhizium anisopliae s.l. for controlling the cattle tick Rhipicephalus microplus.

The effects of two different products - Metarril® SP Organic (dry conidia) and Metarril® SC Organic (emulsifiable concentrated conidia in vegetable oil) - on eggs, larvae and Rhipicephalus microplus engorged females were here explored. Three concentrations (108, 107, and 106 conidia mL-1) for both products were prepared in water + 0.1% Tween® 80 (v/v); afterward, bioassays were carried out for all R. microplus stages by immersion in suspensions (Metarril® SP) or formulations (Metarril® SC). Metarril® SP suspensions showed low efficacy and did not affect biological parameters of treated engorged females; for eggs and larvae, only slight decreases in hatchability and larvae population were observed. Despite a delay in germination, Metarril® SC presented better results; for females, reductions in Egg Mass Weight (EMW) and Egg Production Index (EPI) were reported. On eggs, 108 conidia mL-1 increased Incubation Period (IP), shortened Hatching Period (HP) and decreased hatchability by up to 61%; for larvae, 107 and 108 conidia mL-1 reached 99.6 and 100% larval mortality respectively, 10 days after fungal exposure. Thus, further studies involving the use of oil-based formulations for ticks such as Metarril® SC need to be performed, especially to control the most susceptible stages (eggs and larvae).

Repellency effect of Pilocarpus spicatus A. St.-Hil essential oil and nanoemulsion against Rhipicephalus microplus larvae.

Rhipicephalus microplus, the cattle tick, is a major cause of economic losses in bovine production. Due to the widespread acaricidal resistance to commercially available products, as well as their toxicity and environmental impact, alternative control methods are required. Nanoformulations produced from plant extracts as bioactive substances are very promising as innovative acaricidal agents. Thus, the aim of this study was to evaluate the in vitro repellent activity of Pilocarpus spicatus essential oil and its nanoemulsion against R. microplus, using larval repellent test (RT). The essential oil was extracted by hydrodistillation, using a Clevenger-type apparatus. The nanoemulsion was prepared with 5% essential oil, 5% tween 80, and 90% water, using the phase inversion method (50 mg/mL). Limonene was the major component (46.8%) of the essential oil, as determined by gas chromatography-mass spectrometry (GC/MS) and confirmed by flame ionization detection (GC/FID). According to the RT results, the essential oil had a repellent activity greater than 69%, from concentrations of 3.12 mg/mL (69.81 ± 10%) to 50 mg/mL (98.10 ± 0.6%), whereas the nanoemulsion at 50 mg/mL presented repellent activities of 97.14 ± 1.37% and 97.89 ± 0.52% 6 and 10 h after treatment, respectively. These values regarding to total repellency were very close to those calculated for mortality corrected by Abbott's formula. The phase inversion method preserved the chemical and physical characteristics of the essential oil since both reached an equal repellent effect at the same concentration. Therefore, P. spicatus essential oil and nanoemulsion had excellent repellent activities against R. microplus larvae, demonstrating its potential for future use as an alternative for tick control.

Metarhizium anisopliae sensu lato (s.l.) oil-in-water emulsions drastically reduced Rhipicephalus microplus larvae outbreak population on artificially infested grass.

Rhipicephalus microplus Canestrini, 1887 (Arachnida: Ixodidae) is a mandatory bloodsucking ectoparasite, and it is considered one of the main sanitary problems in livestock. In the development of new technologies for controlling ticks, Metarhizium anisopliae complex (M. anisopliae s. l.) Sorokin, 1883 (Ascomycota: Clavicipitaceae) have been shown to be an effective and safe alternative. However, when applied in the field, abiotic factors may directly influence their microbial activity, and different oily adjuvants enhance fungal efficacy, stability and viability under environmental conditions. Here, the efficacy of two Metarhizium anisopliae s.l. isolates (CG 148 and CG 347) were compared in mineral oil (MO) or vegetable oil (VO) emulsions to control cattle ticks under semi-natural conditions, as well as their persistence in the soil over time. Engorged female ticks were placed on the soil of grass pots previously treated or not with conidial oil-in-water emulsions. Both M. anisopliae s.l. oil-in-water emulsions tested were able to control R. microplus, achieving up to 100% daily efficacy, and remained viable in the soil for up to 60 days after treatment. These results show the prospective applicability of Metarhizium spp. to control the cattle tick and a real possibility for its control in the environment.

Evaluation of rotational grazing as a control strategy for Rhipicephalus microplus in a tropical region.

Rhipicephalus microplus is the most significant tick of livestock and its control is particularly challenging due to its resistance to commercial acaricides. Pasture rotation is considered a management strategy that could help control R. microplus, however, the literature only contemplates mathematical models and little is known about the effects of this practice in the field. The objective of this work was to determine whether pasture rotation is an efficient method for controlling R. microplus. Two different experiments were performed that involved groups of continuous and rotational grazing bovines. Female ticks measuring 4.5-8.0 mm were counted on animals while larvae in pasture were counted using the flannel drag technique. Treatment for infested bovines was applied when the average group tick count was ≥30 females. The results showed that rotational grazing (with 20-day periods of rest) had a higher tick count on-host than continuous grazing (P < 0.05) and additional bovine treatment was needed. Sixty and 105 days were needed to re-infest and disinfest pasture of R. microplus larvae, respectively. The first treatment of bovines occurred 91 days after the animals were placed in a closed area. The results indicate that rotational grazing is not an efficient way to control R. microplus.

Management strategies to minimize the use of synthetic chemical acaricides in the control of the cattle tick Rhipicephalus (Boophilus) microplus (Canestrini, 1888) in an area highly favourable for its development in Argentina.

The aim of this work was to test the efficacy of winter-spring control strategies against Rhipicephalus (Boophilus) microplus (Canestrini, 1888) (Ixodida: Ixodidae) in an area highly favourable for its development in Argentina. Control schemes using three or four annual applications of synthetic acaricides were evaluated. Furthermore, the dynamics of the non-parasitic phases of R. microplus were analysed to provide a framework for the application of pasture spelling as a tool for tick control. The treatment schemes provided appropriate levels of efficacy against R. microplus and also prevented the occurrence of the major peak in abundance of this tick in autumn. A significant overall effect against R. microplus can be achieved when the control strategies tested in this study are applied within the area most ecologically favourable for this tick in Argentina. Analysis of the dynamics of the non-parasitic phase of R. microplus indicates that the spelling period required to achieve a significant reduction of larvae in pastures fluctuates between 12 and 17 weeks if spelling is initiated in spring or early summer, but between 20 and 28 weeks if spelling is started in late summer, autumn or winter.