Resumen: En Uruguay la problemática de la resistencia de Rhipicephalus microplus a los acaricidas habilitados ha ido incrementando con los años, agravándose con la aparición de poblaciones multirresistentes en 2009. El objetivo del trabajo fue analizar la resistencia de 47 poblaciones de garrapatas entre los años 2017 y 2018 para cinco grupos químicos: piretroides (cipermetrina, flumetrina), organofosforados (ethion), amidinas (amitraz), fenilpirazoles (fipronil) y lactonas macrocíclicas (ivermectina), utilizando el Test de Paquete de Larvas (TLP) y una encuesta que se realizaba al responsable del establecimiento. De las 47 poblaciones analizadas 46 fueron resistentes a piretroides (46 cipermetrina, 45 flumetrina), presentando en su mayoría un alto nivel de resistencia. Todas las poblaciones muestreadas presentaron resistencia al menos a un grupo químico. El 68,1 % a tres o más grupos químicos de forma simultánea pero ninguna presentó resistencia ni susceptibilidad a los cinco analizados. Hubo poblaciones que presentaron resistencia a algunos grupos químicos que no habían sido utilizados en los establecimientos de los que fueron muestreadas. La mayoría de los predios realizaron un número mayor de tratamientos al año que el recomendado para un tratamiento generacional. Para todos los principios activos evaluados hubo poblaciones con sospechas de resistencia que no se confirmaron mediante TPL. Esto refleja las situaciones complejas que presentan hoy estos establecimientos en torno a la resistencia a los acaricidas por parte de R. microplus, que podría estar vinculada al modo, frecuencia y tiempo de uso de estos acaricidas. Así como también a su uso pero con otros fines y a los movimientos, ingresos principalmente, de animales a los predios.

Summary: Acaricide resistance of Rhipicephalus microplus tick in Uruguay means a serious problem that has been worsening through years hitting a high point with the detection of multiresistant populations on 2009. Therefore, the aim of this study was to analyze resistance for five chemical groups: pyrethroids (cypermethrin, flumethrin), organophosphates (ethion), amidines (amitraz), phenylpyrazoles (fipronil), macrocyclic lactones (ivermectin) on 47 populations between years 2017 and 2018 by using the Larval Packet Test (LPT) and a quiz made to the responsible for the farm. Results show that 46 from the 47 populations analyzed were resistant to pyrethroids (46 to cypermethrina, 45 to flumethryn). This chemical group also showed the largest number of resistant populations with a high grade of resistance. Every population showed to be resistant to at least one chemical group furthermore the 68.1 % of the populations were resistant to at least 3 chemical groups simultaneously but no population was diagnosed resistant to the 5 chemical groups analyzed neither to be susceptible to all 5 chemical groups. It stands out that there were populations resistant to some chemical groups that the farms of origin had never used. There were registered a higher number of treatments done per year to control R. microplus, than the one recommended for a generational treatment. For every active ingredient evaluated, there were suspicions of resistance that the Larval Packet Test could not confirm. This reflects the complex situation of these farms in what refers to acaricide resistance of R. microplus. This may be related to the way, frequency and time acaricides had been used on these farms, as well as using them for other purposes and also due to the impact of the income of animals infested with R. microplus from other origins.

RESUMO: O fipronil foi registrado no Uruguai em 1997 e, desde então, tem sido utilizado no controle de Haematobia irritans irritans e Rhipicephalus microplus. O objetivo do presente estudo foi avaliar a susceptibilidade de populações de campo de H. irritans ao fipronil. Além disso, foi realizada uma pesquisa para avaliar a utilização de fipronil e as práticas de controle de H. irritans nas fazendas de onde provinham as moscas. Para os bioensaios, 31 populações de campo de H. irritans foram expostas a 10 concentrações de fipronil (3,2-16,0μg.cm2), e seus valores de CL50 foram calculados usando análise probit. Um bioensaio foi realizado com H. irritans da colônia suscetível mantida no USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory para comparação e cálculo das razões de resistência (RRs). Todas as 31 populações de campo pesquisadas no estudo eram suscetíveis ao fipronil, com taxas de resistência variando de <0,5 à 2,2. Quatro populações com Rrs >1 não diferiram significativamente da cepa suscetível. Uma única população apresentou RR >2,2. No geral, o fipronil tinha sido usado principalmente para o controle de R. microplus, e em apenas três fazendas, que estavam livres de R. microplus, o fipronil era utilizado para o controle da H. irritans. Em 17 fazendas não tinha sido utilizado fipronil nos últimos três anos. Conclui-se que no Uruguai as populações de H. irritans no campo permanecem suscetíveis ao fipronil.

ABSTRACT: Fipronil was registered in Uruguay in 1997, and, since then, it has been used for the control of Haematobia irritans irritans and Rhipicephalus microplus. The susceptibility of H. irritants to this drug has not been evaluated. Therefore, the goal of the present study was to evaluate the resistance of H. irritans to fipronil. Additionally, a survey was carried out with the farmers to evaluate the use of fipronil for H. irritans control in the ranches where the flies came from. For the bioassays, 31 field populations of H. irritans were exposed to 10 concentrations of fipronil (3.2-16.0μg.cm2), and their LC50 values were calculated using probit analysis. A bioassay was performed with horn flies from the susceptible colony maintained at the USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory for comparison and calculation of resistance ratios (RRs). All 31 field populations surveyed in the study were susceptible to fipronil, with resistance ratios ranging from <0.5 to 2.2. Four populations with RRs >1 did not differ significantly from the susceptible strain. A single population showed an RR >2.2. Overall, the survey shows that fipronil was mostly used for R. microplus control, and in only three ranches, which were free of R. microplus, was fipronil used for horn fly control. Seventeen farmers did not use fipronil at all in the last three years. It is concluded that, in Uruguay, field populations of horn flies remain susceptible to fipronil.

Resumo Para identificar vacas susceptíveis e resistentes à Haematobia irritans, moscas-dos-chifres foram contadas quinzenalmente durante três anos em 25 vacas de um rebanho Sindhi. Modelos lineares de medidas repetidas foram criados, analisando os resultados de duas formas: 1) pela contagem das moscas, considerando susceptíveis as vacas nas quais a infestação aparecia no quartil superior mais de 50% das semanas e no quartil inferior menos de 20% das semanas. Vacas resistentes foram consideradas aquelas nas quais o número de moscas apareceu no quartil inferior mais de 50% das semanas e no quartil superior menos de 20% das semanas; 2) pela melhor predição linear não-viesada (BLUP), para avaliar o efeito das vacas na contagem de moscas. As vacas foram consideradas susceptíveis quando apareciam no percentil 90 dos BLUPs e resistentes quando apareciam no percentil 10. O método observacional identificou 8% a 20% de indivíduos resistentes e 8% a 12% de susceptíveis. O método dos BLUPs identificou igual taxa de 12% de indivíduos susceptíveis e resistentes. A forte concordância entre estes dois métodos sugere que as vacas susceptíveis podem ser identificadas pela contagem das moscas, o que permite estabelecer seleção dos animais resistentes ou tratamento ou eliminação dos mais susceptíveis.

Abstract To identify susceptible and resistant Haematobia irritans cows, horn flies were counted biweekly for 3 years in a herd of 25 Sindhi cows. Repeated measures linear mixed models were created including cow as a random factor. The results were analyzed by: 1) observing horn fly counts, considering fly-susceptible cows with infestations appearing in the upper quartile more than 50% of the weeks and in the lower quartile less than 20% of the weeks, and fly-resistant cows those that the number of flies was in the lower quartile more than 50% of the weeks and in the upper quartile less than 20%; 2) by the best linear unbiased predictions (BLUPs), to evaluate the cow effect on fly counts. Fly-susceptible cows were those in which the infestation appeared in the 90th percentile of the BLUPs, whereas fly-resistant cows appeared in the 10th percentile. For the observational method the individuals identified as resistant varied between 8% and 20% and 8% to 12% were susceptible. For the BLUP method, the rates of susceptible and resistant cows were 12%. The agreement among methods suggests that susceptible cows can be identified by observations of fly counts, allowing for selective breeding, culling or treatment.

Resumen La babesiosis y la anaplasmosis, son endémicas en Uruguay y producen pérdidas económicas de aproximadamente 14 millones de dólares anuales. Para prevenir estas enfermedades existen vacunas disponibles comercialmente en forma refrigerada o congelada. A pesar de la disponibilidad de vacunas, la cobertura de vacunación es muy baja. Las causas del bajo número de vacunas utilizadas pueden ser varias: falta de información por parte de los productores y veterinarios; dificultades en el manejo y conservación de las vacunas; y costos por dosis y aplicación. Con el objetivo de comparar la eficacia de la vacuna refrigerada con la congelada contra Babesia bovis, Babesia bigemina y Anaplasma marginale fue realizado un ensayo en un establecimiento comercial ubicado en el departamento de Tacuarembó, donde 57 terneras raza Brangus fueron vacunadas con la vacuna refrigerada y 58 con la vacuna congelada. Para determinar la eficacia de ambas vacunas se realizaron las pruebas de inmunofluorescencia indirecta para B. bovis y B. bigemina y aglutinación en tarjeta para Anaplasma spp. al día 62 postvacunación. No existieron diferencias significativas entre la protección ofrecida por ambas vacunas (p> 0,05), encontrándose entre el 93% y 98,3% de los animales positivos para cada uno de los tres agentes. Este trabajo demuestra que ambas vacunas son eficientes para la profilaxis de la enfermedad y deben ser utilizadas para la protección de bovinos en áreas de inestabilidad enzoótica. Es necesario continuar con las tareas de extensión para aumentar la cobertura de vacunación a nivel nacional e investigar posibles fallas en la vacunación.

Summary Babesiosis and anaplasmosis, are endemic in Uruguay and produce economic losses of approximately 14 million dollars per year. To prevent these diseases, refrigerated or frozen vaccines are commercially available. Despite the availability of vaccines, vaccination coverage is very low probably due to several causes: the lack of information of farmers and veterinarians; difficulties in the management and conservation of the vaccines; and costs per dose and application. In order to compare the efficacy of the refrigerated vaccine with a frozen vaccine against Babesia bovis, Babesia bigemina and Anaplasma marginale we conducted a trial in a commercial farm located in the department of Tacuarembó. Fifty-seven Brangus calves were vaccinated with the refrigerated vaccine and 58 with the frozen vaccine. The indirect immunofluorescence tests for Babesia bovis and Babesia bigemina and the card test for Anaplasma spp. were performed to determine the efficacy of both vaccines at day 62 post vaccination. There were no significant differences between the protection offered by both vaccines (p> 0.05), being between 93% and 98.3% of the animals positive for each of the three agents. These results show that both vaccines are efficient for the prophylaxis of the disease and should be used for the protection of bovines in areas of enzootic instability. It is necessary to continue with the extension tasks to increase the national coverage of vaccinated animals and to investigate possible vaccine failure.