Molecular biology of amitraz resistance in cattle ticks of the genus Rhipicephalus

Amitraz is an important product for the control of cattle ticks around the world. In comparison with other products for the control of ticks, it is quite affordable and it has a rapid knock-down effect. It binds with and activates adrenergic neuro-receptors of animals and it inhibits the action of monoamine oxidases (MAO). Resistance to amitraz has been documented in Rhipicephalus microplus, R. decoloratus and R. appendiculatus. Four mechanisms of resistance have been proposed, each of which is supported by evidence but none of which has been definitively confirmed as the cause of resistance in the field. The proposed mechanisms include genetic target site insensitivity in two G protein-coupled receptors, the beta-adrenergic octopamine receptor (BAOR) and the octopamine/tyramine receptor (OCT/Tyr), increased expression or activity of monoamine oxidases and increased expression or activity of the ATP binding cassette transporter

Strategies for the control of Rhipicephalus microplus ticks in a world of conventional acaricide and macrocyclic lactone resistance

Infestations with the cattle tick, Rhipicephalus microplus, constitute the most important ectoparasite problem for cattle production in tropical and subtropical regions worldwide, resulting in major economic losses. The control of R. microplus is mostly based on the use of conventional acaricides and macrocyclic lactones. However, the intensive use of such compounds has resulted in tick populations that exhibit resistance to all major acaricide chemical classes. Consequently, there is a need for the development of alternative approaches, possibly including the use of animal husbandry practices, synergized pesticides, rotation of acaricides, pesticide mixture formulations, manual removal of ticks, selection for host resistance, nutritional management, release of sterile male hybrids, environmental management, plant species that are unfavourable to ticks, pasture management, plant extracts, essential oils and vaccination. Integrated tick management consists of the systematic combination of at least two control technologies aiming to reduce selection pressure in favour of acaricide-resistant individuals, while maintaining adequate levels of animal production. The purpose of this paper is to present a current review on conventional acaricide and macrocyclic lactone resistance for better understanding and control of resistant ticks with particular emphasis on R. microplus on cattle

Identification of a novel ß-adrenergic octopamine receptor-like gene (ßAOR-like) and increased ATP-binding cassette B10 (ABCB10) expression in a Rhipicephalus microplus cell line derived from acaricide-resistant ticks

Background: The cattle tick Rhipicephalus (Boophilus) microplus is an economically important parasite of livestock. Effective control of ticks using acaricides is threatened by the emergence of resistance to many existing compounds. Several continuous R. microplus cell lines have been established and provide an under-utilised resource for studies into acaricide targets and potential genetic mutations associated with resistance. As a first step to genetic studies using these resources, this study aimed to determine the presence or absence of two genes and their transcripts that have been linked with acaricide function in cattle ticks: β-adrenergic octopamine receptor (βAOR, associated with amitraz resistance) and ATP-binding cassette B10 (ABCB10, associated with macrocyclic lactone resistance) in six R. microplus cell lines, five other Rhipicephalus spp. cell lines and three cell lines representing other tick genera (Amblyomma variegatum, Ixodes ricinus and Hyalomma anatolicum). Methods: End-point polymerase chain reaction (PCR) was used for detection of the βAOR gene and transcripts in DNA and RNA extracted from the tick cell lines, followed by capillary sequencing of amplicons. Quantitative real-time PCR (qPCR) was performed to determine the levels of expression of ABCB10. Results: βAOR gene expression was detected in all Rhipicephalus spp. cell lines. We observed a second amplicon of approximately 220 bp for the βAOR gene in the R. microplus cell line BME/CTVM6, derived from acaricide-resistant ticks. Sequencing of this transcript variant identified a 36 bp insertion in the βAOR gene, leading to a 12-amino acid insertion (LLKTLALVTIIS) in the first transmembrane domain of the protein. In addition, nine synonymous SNPs were also discovered in R. appendiculatus, R. evertsi and R. sanguineus cell lines. Some of these SNPs appear to be unique to each species, providing potential tools for differentiating the tick species. The BME/CTVM6 cell line had significantly higher ABCB10 (P = 0.002) expression than the other R. micropluscell lines. Conclusions: The present study has identified a new βAOR gene and demonstrated a higher ABCB10 expression level in the BME/CTVM6 cell line, indicating that tick cell lines provide a useful experimental tool for acaricide resistance studies and further elucidation of tick genetics

Evaluating health risks from occupational exposure to pesticides and the regulatory response.

In this study, we used measurements of occupational exposures to pesticides in agriculture to evaluate health risks and analyzed how the federal regulatory program is addressing these risks. Dose estimates developed by the State of California from measured occupational exposures to 41 pesticides were compared to standard indices of acute toxicity (LD50) and chronic effects (reference dose). Lifetime cancer risks were estimated using cancer potencies. Estimated absorbed daily doses for mixers, loaders, and applicators of pesticides ranged from less than 0.0001% to 48% of the estimated human LD50 values, and doses for 10 of 40 pesticides exceeded 1% of the estimated human LD50 values. Estimated lifetime absorbed daily doses ranged from 0.1% to 114,000% of the reference doses developed by the U.S. Environmental Protection Agency, and doses for 13 of 25 pesticides were above them. Lifetime cancer risks ranged from 1 per million to 1700 per million, and estimates for 12 of 13 pesticides were above 1 per million. Similar results were obtained for field workers and flaggers. For the pesticides examined, exposures pose greater risks of chronic effects than acute effects. Exposure reduction measures, including use of closed mixing systems and personal protective equipment, significantly reduced exposures. Proposed regulations rely primarily on requirements for personal protective equipment and use restrictions to protect workers. Chronic health risks are not considered in setting these requirements. Reviews of pesticides by the federal pesticide regulatory program have had little effect on occupational risks. Policy strategies that offer immediate protection for workers and that are not dependent on extensive review of individual pesticides should be pursued

Livestock and livestock buildings

Description based on: 1985

Manejo Integrado de Plagas para el control de Varroa destructor y sus implicaciones para las colonias de Apis mellifera

Integrated Pest Management (IPM) is a pest management system that, in the socioeconomic context of farming systems, the associated environment and the population dynamics of the pest species, utilizes all suitable techniques in a compatible manner as possible to maintain the pest population levels below those causing economic injury. This article covers the principal aspects of the interaction between Apis mellifera and Varroa destructor and it describes the classical control forms applied to reduce the mite negative impact on colonies. Some examples of IPM activities that have been done to control this parasite in the southeast of Buenos Aires province, Argentina have shown good results. Several products worldwide have shown good effectiveness as well. Nevertheless, there are certain risks and hazards inherent to their use, such as: their negative impact on human health, resistance phenomena, loss of beneficial insects and native fauna, environmental pollution and drug residues in the hive products harmful for human consumption. The development of acaricide resistance in V. destructor populations and the possibility of incorporating contaminants in colonies by means of this type of treatment have promoted the addition of new molecules to minimize these disadvantages. The application of organic acids, essential oils and their components have become a worthwhile alternative. It can be concluded that to achieve an integrated management of V. destructor entails a change of mind for beekeepers and the active participation of all actors involved in the beekeeping sector to promote scientific activities aimed to discovering and developing new tools to be incorporated in an IPM Program against V. destructor.El Manejo Integrado de Plagas (MIP) es un sistema de manejo que en el contexto socioeconómico de los sistemas agrícolas, asociado al ambiente y a la dinámica poblacional de las especies plaga, utiliza las técnicas apropiadas de una manera compatible para mantener, las poblaciones de la plaga por debajo de los niveles que causan daño económico. Este artículo cubre los principales aspectos de la interacción entre Apis mellifera y Varroa destructor y describe las formas clásicas de control aplicadas para reducir el impacto del ácaro en las colonias. Algunos ejemplos de las actividades de manejo integrado de plagas realizadas para controlar este parásito en el Sureste de la provincia de Buenos Aires, Argentina, mostraron buenos resultados. Existen algunos productos acaricidas de síntesis en el mundo, que presentaron buena efectividad. Sin embargo, el desarrollo de resistencia a los acaricidas en poblaciones de V. destructor y la posibilidad de incorporación de contaminantes en las colonias por este tipo de tratamientos, se han transformado en cuestiones de gravedad. Esto ha promovido la búsqueda de nuevas moléculas para minimizar estas desventajas. Ácidos orgánicos, aceites esenciales y sus componentes se han convertido en una valiosa alternativa. El éxito de la implementación de herramientas para el Manejo Integrado de Varroa involucra un cambio de mentalidad en los apicultores y la participación activa de todos los actores del sector apícola, para promover actividades científicas que ayuden a desarrollar nuevas alternativas para ser incorporadas en Programas Regionales de Manejo Integrado de esta parasitosis.Fil: Ruffinengo, Sergio Roberto. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias. Departamento de Producción Animal. Cátedra de Apicultura; ArgentinaFil: Maggi, Matías Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biología. Laboratorio de Artrópodos; ArgentinaFil: Marcangeli, Jorge Augusto. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biología. Laboratorio de Artrópodos; ArgentinaFil: Eguaras, Martin Javier. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biología. Laboratorio de Artrópodos; ArgentinaFil: Principal, Judith. Universidad Centroccidental “Lisandro Alvarado”. Lara; VenezuelaFil: Barrios, Carlos. Universidad Centroccidental “Lisandro Alvarado”. Lara; VenezuelaFil: de Piano, Fiorella Giselle. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Giullia, Mitton. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentin

Acaricides for eradication of the tick Amblyomma variegatum in the Caribbean

Le succés d'une campagne d'éradication de la tique Amblyomma variegatum dans les Caraïbes impose l'utilisation d'acaricides efficaces, si possible rémanents, faciles d'emploi, ne necessitant pas le recours à de l'eau pour la préparation de liquides dilués, ni à des équipements coûteux pour le transport et l'application. Des test de sensibilité in vitro conduits sur des souches de Porto Rico et de Guadeloupe ainsi que l'observation de l'impact des campagnes de détiquage conduites dans les Caraïbes semblent indiquer qu'il n'y a pas dans la région de problèmes de résistance aux acaricide

Results of international standardised beekeeper surveys of colony losses for winter 2012-2013 : analysis of winter loss rates and mixed effects modelling of risk factors for winter loss.

This article presents results of an analysis of winter losses of honey bee colonies from 19 mainly European countries, most of which implemented the standardised 2013 COLOSS questionnaire. Generalised linear mixed effects models (GLMMs) were used to investigate the effects of several factors on the risk of colony loss, including different treatments for Varroa destructor, allowing for random effects of beekeeper and region. Both winter and summer treatments were considered, and the most common combinations of treatment and timing were used to define treatment factor levels. Overall and within country colony loss rates are presented. Significant factors in the model were found to be: percentage of young queens in the colonies before winter, extent of queen problems in summer, treatment of the varroa mite, and access by foraging honey bees to oilseed rape and maize. Spatial variation at the beekeeper level is shown across geographical regions using random effects from the fitted models, both before and after allowing for the effect of the significant terms in the model. This spatial variation is considerable

Eficacia de la ivermectina oral en el tratamiento de la sarna demodécica canina resistente al almitraz

Se describen dos casos de sarna demodécica canina resistente al amitraz, tratados con ivermectina por vía oral a dosis de 600 mcg/kg durante 3 y 5 meses respectivamente.Two cases of amitraz-resistant generalized demodicosis treated with ivermectin 600 mcg/kg during 3 and 5 months respectiuely

Premedication with amitraz or xylazine for anesthetic induction of cattle with ketamine

Os agonistas alfa-2 são muito utilizados como medicação pré-anestésica na espécie bovina, promovendo sedação, analgesia e miorrelaxamento, enquanto a cetamina, em virtude de suas propriedades analgésicas e simpatomiméticas, tem ótimo uso na indução anestésica. Com isso, estudaram-se os efeitos clínicos e cardiovasculares da indução anestésica intravenosa por cetamina em 21 bovinos pré-tratados com xilazina ou amitraz pela via intravenosa. A cetamina aumentou a freqüência cardíaca nos grupos amitraz e controle, o que não ocorreu no grupo xilazina. Houve aumento da pressão arterial sistólica durante os primeiros cinco minutos após a administração dos agonistas alfa-2. A freqüência respiratória elevou-se após a administração de cetamina até os 25 minutos, independentemente do prétratamento. A motilidade rumenal diminuiu durante todo o período experimental nos grupos que receberam agonistas alfa-2. A anestesia dissociativa produziu fasciculações e contrações musculares nos grupos amitraz e controle. Concluiu-se que os efeitos do amitraz foram similares aos da xilazina, porém esta última promoveu maior sedação e relaxamento muscular, abolindo os efeitos catalépticos da cetamina. Ambos os protocolos anestésicos mostraram-se seguros para o uso em bovinos, porém a xilazina demonstrou melhor opção na medicação pré-anestésica. __________________________________________________________________________________________ ABSTRACTThe alpha-2 agonists have sedative, analgesic and muscle relaxation properties in cattle. The ketamine is useful in anesthetic protocols as an inductor agent and it produces analgesia and anesthesia. The combination of ketamine with other drugs is necessary considering that it causes deleterious effects like catalepsy and muscle spasticity if given alone. This study evaluated clinical and behavioral effects of xylazine-ketamine or amitraz-ketamine combinations in twenty–one calves. The ketamine increased heart rate in amitraz and control groups. The respiratory rate increased in all experimental groups, restoring the basal values after 25 minutes. The ruminal motility was kept inhibited along whole observation period. It was concluded that xylazine-ketamine combination produced better sedation and muscle relaxation than amitraz-ketamine combination, characterized by a larger incidence of recumbency and by the absence of catalepsy. Both anesthetic protocols were safe for use in cattle, however, xylazine showed a better option as a preanesthetic medication