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

Infestation of rabbits with just-molted adults of the cattle tick Rhipicephalus microplus: biological parameters and efficiency / Infestação de coelhos com adultos recém-mudados do carrapato-do-boi Rhipicephalus microplus

In this study, we report for the first time the successful infestation of rabbits with just-molted, unfed adults of Rhipicephalus microplus. Six New Zealand White rabbits were experimentally infested with 20 female and 20 male unfed adult ticks released into plastic chambers fixed on the shaved backs of each host. The attachment and feeding processes were successful. The biological characteristics of the ticks and the occurrence of adverse events in the tick-attachment area were studied. The average engorgement period was 10.7 days, and 33.3% of the engorged females completed the parasitic phase. The average weight of the recovered engorged females was 149.8 mg, with an average egg mass weight of 70.9 mg, a conversion efficiency index of 47.3%, and a hatching percentage of 88.31%. The adverse reactions found in the tick-attachment area were the usual inflammatory responses of the organism to infestation by these ectoparasites; however, it did not prevent the ticks from feeding and completing their life cycle. These data indicate that the infestation of rabbits with just-molted, unfed adult ticks could be a valuable, alternative animal model for rapid and economical evaluation of vaccine candidates and new molecules with acaricidal activity against Rhipicephalus microplus.(AU)

Neste estudo, relata-se, pela primeira vez, o sucesso da infestação de coelhos por carrapatos adultos recém-mudados e não alimentados. Seis coelhos brancos da Nova Zelândia foram infestados artificialmente com 20 carrapatos adultos fêmeas e 20 machos adultos não alimentados no interior de câmaras de plástico fixadas no dorso de cada hospedeiro. Os processos de fixação e alimentação dos carrapatos foram bem sucedidos. Foram estudadas as características biológicas dos carrapatos e a ocorrência de eventos adversos na área de fixação do ectoparasito. O período médio de ingurgitamento foi de 10,7 dias, e 33,3% das fêmeas ingurgitadas completaram a fase parasitária. O peso médio das fêmeas ingurgitadas recuperadas foi de 149,8 mg, com peso médio da massa de ovos de 70,9 mg, índice de produção de ovos de 47,3% e porcentagem de incubação de 88,31%. Uma resposta inflamatória usual do organismo à infestação por esses ectoparasitas foi a única reação adversa encontrada na área de fixação dos carrapatos, o que não impediu que eles se alimentassem e completassem seu ciclo de vida. Esses dados apontam que a infestação de coelhos com carrapatos adultos recém-mudados e não alimentados pode ser um modelo animal alternativo e útil para a avaliação rápida e econômica de candidatos a vacinas e novas moléculas com atividade acaricida contra Rhipicephalus microplus.(AU)

Epidemiological aspects of cattle tick fever in Brazil / Aspectos epidemiológicos da tristeza parasitária bovina no Brasil

The present work reviews the epidemiologic situation of Anaplasma marginale and Babesia spp. infections and the occurrence of cattle tick fever outbreaks in Brazil. In areas of tick fever enzootic instability, environmental conditions interfere with the development of Rhipicephalus (Boophilus) microplus: chilly winter in the southern region, floods in the Pantanal, and low humidity in the Caatinga. In contrast, the climatic conditions of stable zones (Cerrado, Amazon and Atlantic Forest biomes) favor tick development. In enzootic areas, tick fever is uncommon because the animals are in frequent contact with the parasite, acquiring immunity naturally during the period of innate resistance; however, outbreaks may occur when calves become infested by considerable numbers of infected ticks during this period or in adults raised in tick-free environments that become infested for the first time when transporting to stable areas. It is necessary to better understand the disease's risk factors under stable conditions and the implications of the mechanical and other vector transmission of A. marginale. To prevent tick fever outbreaks in Brazil, it is important to develop and use anaplasmosis and babesiosis vaccines in cattle from enzootic unstable regions, especially when animals are moved to stable areas.(AU)

O presente trabalho revisa a situação epidemiológica das infecções por Anaplasma marginale e Babesia spp. e a ocorrência de surtos de Tristeza parasitária bovina (TPB) no Brasil. Em áreas de instabilidade enzoótica, as condições ambientais interferem no desenvolvimento do Rhipicephalus (Boophilus) microplus: o frio do inverno na região Sul; as inundações no Pantanal; e a baixa umidade na Caatinga. Por outra parte, as condições climáticas das zonas de estabilidade (os biomas Cerrado, Amazônia e Mata Atlântica) favorecem o desenvolvimento do carrapato. A TPB não é comum nas áreas estáveis, porque os animais estão em contato frequente com os parasitas, adquirindo imunidade naturalmente. Podem, porém, ocorrer surtos quando um número considerável de carrapatos infectados infesta bezerros, durante o período de resistência inata, ou quando adultos que foram criados em ambientes livres de carrapatos infestam-se, pela primeira vez, ao serem transportados para áreas estáveis. É necessário entender melhor os fatores de risco da doença em condições de estabilidade e a implicação da transmissão de A. marginale de forma mecânica, ou por meio de vetores diferentes do carrapato. Para prevenir surtos de TPB, no Brasil, é necessário desenvolver e usar vacinas em bovinos de regiões de instabilidade, especialmente antes de transportá-los para áreas estáveis.(AU)

Association between chronic Anaplasma marginale and Babesia spp. infection and hematological parameters of taurine heifers / Associação entre infecção crônica por Anaplasma marginale e Babesia spp. e parâmetros hematológicos de novilhas taurinas

The aim of this study was to investigate the association between chronic Anaplasma marginale and Babesia spp. infection and hematological parameters of pregnant and non-pregnant taurine heifers. Blood samples from 94 females were collected on the first day (D-10) of timed artificial insemination (TAI) protocol and on pregnancy diagnosis (D+34). Hematological parameters were determined and compared between pregnant (PG) and non-pregnant (NPG) heifers, and within group at different sampling days. Real-time PCR (qPCR) was used to determine A. marginale and Babesia bovis infection, and for absolute quantification of Babesia spp. between PG and NPG groups. Correlation analysis was performed between the number of gDNA copies (CN) of Babesia spp. and hematological parameters. On D-10, mean hemoglobin concentration was higher for NPG, and hematocrit and total plasma protein were higher on D+34 for both groups. There was no difference in Babesia spp. CN between groups. In the first qPCR, all heifers were positive for A. marginale and B. bovis. Significant correlations were found between hemoglobin and erythrocyte and between hemoglobin and hematocrit (r = 0.8082 and r = 0.3009, respectively). Low levels of A. marginale and Babesia spp. did not affect hematological parameters of chronically infected pregnant and non-pregnant taurine heifers.(AU)

O objetivo deste estudo foi investigar a associação entre infecção crônica por Anaplasma marginale e Babesia spp. e parâmetros hematológicos de novilhas taurinas prenhes e não prenhes. Sangue de 94 fêmeas foi coletado no primeiro dia (D-10) do protocolo de inseminação artificial em tempo fixo (IATF) e no diagnóstico de gestação (D+34). Parâmetros hematológicos foram comparados entre novilhas prenhes (PG) e não prenhes (NPG) e dentro dos grupos entre dias de coleta. Usando-se PCR em tempo real (qPCR), determinou-se a infecção por A. marginale e Babesia bovis e quantificação absoluta de Babesia spp. Entre os grupos PG e NPG. A análise de correlação foi realizada entre o número de cópias (CN) de Babesia spp. e parâmetros hematológicos. No D-10, a concentração de hemoglobina foi maior para NPG e hematócrito, e proteína plasmática total foram maiores em D+34 para ambos os grupos. Não houve diferença para CN de Babesia spp. entre os grupos. Na primeira qPCR, todas as novilhas foram positivas para A. marginale e B. bovis. Correlações significativas foram encontradas entre hemoglobina/eritrócito e hemoglobina/hematócrito (r=0,8082 e r=0,3009, respectivamente). Baixos níveis de A. marginale e Babesia spp. não afetaram os parâmetros hematológicos de novilhas taurinas prenhes e não prenhes cronicamente infectadas.(AU)

Antibacterials and behaviors adopted by milk producers in Goiás, Brazil / Antibacterianos e condutas adotadas por produtores de leite em Goiás, Brasil

Milk and its derivatives are rich in nutrients and widely consumed by the population. However, the presence of chemical residues is frequent in these products. This study aimed to carry out a diagnosis of the use of antibacterials and evaluate the knowledge about these drugs and behaviors adopted by dairy producers in Goiás, Brazil. A total of 286 dairy farms in 36 municipalities in the State were visited and interviews were conducted with the owner or auxiliary workforce. The questions addressed the production parameters of the property and the use of antibacterials. The answers were presented in percentages and graphs. Statistical analysis was performed using Pearson's chi-square test at a 5% significance level. Only 26.2% of the producers used antibacterials indicated by veterinarians and all producers (100%) disposed of milk with residues inappropriately. Tetracycline and penicillin were the most used among the 21 cited active principles. Enteritis (22.1%), cattle tick fever (21.1%), and mastitis (19.4%) were the main diseases treated with antibacterials. A total of 37.4% of respondents were unable to distinguish antibacterials from other drugs. Moreover, the more specialized the farm, the greater the veterinary assistance and the greater the care for antibacterial treatments. Most respondents (51.7%) had incomplete elementary education. These results provide important information about how rural producers in the State of Goiás use antibacterials and serve as a basis for future interventions. The need for greater access by producers to veterinary services in Goiás is evident to reduce the unnecessary and inappropriate use of antibacterials.(AU)

O leite e seus derivados são ricos em nutrientes e largamente consumidos pela população. Contudo, a presença de resíduos de substâncias químicas é frequente nesses produtos. Esse estudo objetivou realizar um diagnóstico sobre o uso de antibacterianos, avaliar o conhecimento sobre esses fármacos e condutas adotadas por produtores de leite em Goiás, Brasil. Foram visitadas 286 propriedades leiteiras em 36 municípios do estado, onde foram realizadas entrevistas com o proprietário ou mão de obra auxiliar. As perguntas abordavam parâmetros produtivos da propriedade e uso de antibacterianos. As respostas foram apresentadas em porcentagem e gráficos. A análise estatística foi realizada pelo teste de qui-quadrado de Pearson ao nível de significância de 5%. Apenas 26,2% dos produtores utilizavam antibacterianos indicados por veterinários e todos (100%) descartavam o leite com resíduos de forma inadequada. Dentre os 21 princípios ativos citados, os mais utilizados foram as tetraciclinas e penicilinas. As principais doenças tratadas com antibacterianos foram enterite (22,1%), tristeza parasitária bovina (21,1%) e mastite (19,4%). Observou-se que 37,4% dos entrevistados não souberam distinguir antibacterianos de outros medicamentos. Verificou-se que quanto mais especializada é a fazenda, maior é a assistência veterinária e maiores os cuidados para tratamentos com antibacterianos. A maioria dos entrevistados (51,7%) apresentava ensino fundamental incompleto. Esses resultados fornecem informações importantes sobre como os produtores rurais do estado de Goiás utilizam antibacterianos e servem como base para intervenções futuras. É evidente a necessidade de maior acesso dos produtores a serviços veterinários em Goiás, a fim de reduzir o uso desnecessário e inadequado de antibacterianos.(AU)

Outbreak of bovine tick-borne disease on a riverside property in the Western Amazonia: Case report / Surto de tristeza parasitária bovina em propriedade ribeirinha na Amazônia Ocidental: Relato de caso

The objective was to report an outbreak of tick-borne disease (TBD) on riverside property in the Western Amazon. The death of 25 Nellore cattle was reported on a rural property on the banks of the Purus River, state of Acre. The producer observed animals with staggering walking, drop in productivity, weight loss and evolution to death in approximately 30 days. Fifteen animals from the same batch were selected for clinical evaluation and the ear tip was punctured for hemoparasite research, in addition to blood collection for hematological, biochemical and molecular evaluation. The main laboratory findings were leukocytosis, thrombocytopenia, hypoproteinemia, elevated creatine kinase and reduced urea, creatinine and albumin, as well as visualization of forms suggestive of Anaplasma spp. in 13.33% of the samples. Through PCR, 20% positivity was observed for Anaplasmamarginale and 53.33% for Babesia sp. Hematological and biochemical changes, although highly suggestive, may suffer changes from other factors not related to TBD. Therefore, the presumptive identification of the etiological agent in the blood or confirmatory by molecular methods is essential in the diagnosis. Depending on the stage of the disease, low parasitemia occurs, making it difficult to see hemoparasites in blood smears. The Babesia sp. was the main agent of the outbreak of TBD in the population evaluated, which, when associated with early clinical and laboratory diagnosis, results in adequate therapeutic direction and prophylactic measures, promoting a balance between host, agent and vector.

Objetivou-se relatar um surto de tristeza parasitária bovina (TPB) em propriedade ribeirinha na Amazônia Ocidental. Foi notificado o óbito de 25 bovinos da raça Nelore, em uma propriedade rural às margens do rio Purus, estado do Acre. O produtor observou animais com andar cambaleante, queda na produtividade, perda de peso e evolução ao óbito em aproximadamente 30 dias. Quinze animais do mesmo lote foram selecionados para avaliação clínica e foi procedida a punção a ponta de orelha para pesquisa de hemoparasitos, além da coleta de sangue para avaliação hematológica, bioquímica e molecular. Os principais achados laboratoriais foram anemia, leucocitose, trombocitopenia, hipoproteinemia, elevação da creatina quinase e redução de ureia, creatinina e albumina, além da visualização de formas sugestivas de Anaplasma spp. em 13,33% das amostras. Por meio da PCR, foi observado 20% de positividade para Anaplasma marginale e 53,33% para Babesia sp. As alterações hematológicas e bioquímicas, embora bastante sugestivas, podem sofrer alterações de outros fatores não relacionados à TPB. Por isso, a identificação presuntiva do agente etiológico no sangue ou confirmatória por métodos moleculares é essencial no diagnóstico. A depender da fase da doença, ocorre baixa parasitemia, dificultando a visualização de hemoparasitos em esfregaços sanguíneos. A Babesia sp. foi o principal agente do surto de TPB na população avaliada, que, quando associado ao diagnóstico clínico e laboratorial precoce, resulta no direcionamento terapêutico adequado e medidas profiláticas, promovendo uma relação de equilíbrio entre hospedeiro, agente e vetor.

Occurrence of ticks and tick-borne mixed parasitic microbiota in cross-bred cattle in District Lahore, Pakistan / Ocorrência de carrapatos e microbiota parasitária mista transmitida por carrapatos em bovinos mestiços no distrito de Lahore, Paquistão

The present study was focused on the incidence of ticks and tick-borne diseases (TTBD) in cross-bred cattle (Friesian x Sahiwal) of two farms (n = 2548) in district Lahore, Pakistan. We collected total of 572 ticks (adults and nymphs) and blood samples (10 ml) for microscopic i.e., blood smear test ­ Giemsa Stain (BST) and molecular analysis; Reverse Line Blot-General Primer-PCR (RLB-PCR) and Specie Specific Primer PCR (SP-PCR) from infested cattle (n = 100) from months of April to September. Results: The tick specie identified was Rhipicephalus microplus at both farms, with significant difference in infestations rate amongst both farms (p< 0.0001). The cross-bred cattle having higher ratio of Friesian blood and lower ratio of Sahiwal blood were mostly infested by ticks (p < 0.0458) and haemoparasites (p <0.474) and vice versa. The SP-PCR showed higher number of haemoparasites infection than BST, which revealed 16% T. annulata (p < 0.0001 and k value 0.485, 0.0001), 51% B. bigemina (p < 0.0001 and k value 0.485, 0.0001) and 15% A. marginale (p < 0.001 and k value 0.207, 0.001), respectively. The single infection with B. bigemina was 34% (n = 34/100) and A. marginale 6% (n = 6/100). The double infection with T. annulata/B. bigemina was 8% (n = 8/100) and B. bigemina/A. marginale 1% (n = 1/100). Whereas the triple infection with T. annulata/B. bigemina/A .marginale was 8% (n = 8/100). The phylogenetic study of isolated sequence of T. annulata revealed close homology to isolates from Iran (87%), B. bigemina to isolates from Cuba (94 to 100%) and A. marginale with isolates from Pakistan (99 to 98%).

O presente estudo foi enfocado na incidência de carrapatos e doenças transmitidas por carrapatos (TTBD) em bovinos mestiços (Friesian x Sahiwal) de duas fazendas (n = 2.548) no distrito de Lahore, Paquistão. Foram coletados 572 carrapatos (adultos e ninfas) e amostras de sangue (10 ml) para microscopia, ou seja, esfregaço sanguíneo ­ coloração de Giemsa (BST) e análise molecular; Reverse Line Blot-General Primer-PCR (RLB-PCR) e Specific Primer PCR (SP-PCR) ­, de bovinos infestados (n = 100) nos meses de abril a setembro. Resultados: A espécie de carrapato identificada em ambas as fazendas foi Rhipicephalus microplus, com diferença significativa na taxa de infestação nos dois locais (p < 0,0001). Os bovinos mestiços Friesian, com maior proporção de sangue, e Sahiwal, com menor proporção de sangue, foram principalmente infestados por carrapatos (p < 0,0458) e hemoparasitos (p < 0,474), e vice-versa. O SP-PCR mostrou maior número de infecção por hemoparasitos do que a BST, revelando 16% de Theileria annulata (p < 0,0001; k valor 0,485; 0,0001), 51% de Babesia bigemina (p < 0,0001; k valor 0,485; 0,0001) e 15% de Anaplasma marginale (p < 0,001; valor de k 0,207; 0,001). A infecção única com B. bigemina foi de 34% (n = 34/100), e com A. marginale, de 6% (n = 6/100). A dupla infecção com T. annulata/B. bigemina foi de 8% (n = 8/100), e com B. bigemina/A. marginale, de 1% (n = 1/100). Já a tripla infecção com T. annulata/B. bigemina/A. marginale foi de 8% (n = 8/100). O estudo filogenético da sequência isolada de T. annulata revelou estreita homologia com isolados do Irã (87%), de B. bigemina com isolados de Cuba (94 a 100%) e de A. marginale com isolados do Paquistão (98 a 99%).

ISOLATION AND AMPLIFICATION OF Anaplasma marginale IN CHICKEN EMBRYO FIBROBLAST CELL CULTURE / ISOLATION AND AMPLIFICATION OF Anaplasma marginale IN CHICKEN EMBRYO FIBROBLAST CELL CULTURE

Anaplasma marginale is an important agent for animal livestock, its presence in herds of cattle, sheep and goats leads to losses for Brazilian agribusiness. The present study aimed to describe an isolation technique for A. marginale, using chicken embryo fibroblast (CEF) cell culture. For this, blood and tick samples were collected from 5 calves, between 2 and 3 months of age, which due to anemia, jaundiced mucous membranes and prostration, were considered supposedly infected with A.marginale. For the diagnosis, DNA extraction and PCR was performed from the blood and tick samples collected. All the tick and blood samples were positive in the PCR test. Additionally, ticks were crushed with the aid of a blender for inoculation in CEF cell culture. After inoculation, the cultures were kept at 37ºC and 5% CO2 for 15 days. The cell supernatant of cell cultures were again analyzed by PCR and by the technique Wrighte stain to confirm A. marginale isolation. Cell cultures were positive in PCR and the presence of the agent was demonstrated by Wrighte stain. Therefore, using CEF cell culture was possible to isolate and amplify the A. marginale in a concentration of 1.3 x 107.2 bodies per ml. The CEF cells are undemanding, easy to maintain and they are an option for isolation and production of A. marginale in the laboratory condition.

Anaplasma marginale (A. marginale) is a worldwide pathogen that infects a variety ofruminants, but mostly cattle. The present study aimed to describe an isolation technique for A. marginale, using chicken embryo Þ broblast (CEF) cell culture. Blood and tick samples were collected from 5 calves from 2 to 3 months old, which were considered to be infected with A.marginale due to anemia, jaundiced mucous membranes, and prostration. DNA extractionand PCR were performed for diagnosis using blood and tick samples. All tick and blood samples tested positive in PCR. Additionally,ticks were crushed with the aid of a blender for inoculation in CEF cell culture. After inoculation, the cultures were kept at 37ºC and 5%CO2 for 15 days. The cell supernatant of cell cultures was again analyzed using PCR and Wright stain method to conÞ rm A. marginaleisolation. Cell cultures tested positive in PCR, and the presence of the agent was demonstrated by Wright stain. Therefore, by using CEFcell culture it was possible to isolate and amplify the A. marginale in a concentration of 1.3x 107.2 bodies per mL. The CEF cells are undemanding and easy to preserve; they are anoption for isolation and production of A. marginale under laboratory conditions.

Acaricidal effect of major compounds to control Rhipicephalus microplus (Canestrini, 1887) in dairy cows and possible alternatives for reversing multidrug resistance / Efeito acaricida dos principais compostos no controle de Rhipicephalus microplus (Canestrini, 1887) em vacas leiteiras e possíveis alternativas para reverter a resistência múltipla às drogas

Tick control represent a great challenge to animal health. The objective of this study was to evaluate the efficacy of acaricidal compounds against Rhipicephalus microplus from dairy cattle systems in Paraná State, Brazil. Six farms (PR1-PR6) were selected, where anti-tick products were applied at fixed intervals. Two other farms that adopted alternative protocols; target selective treatment (PRS), and individual-based agroecological protocol (PRA) were also included in the trial. Fully engorged R. microplus were collected for the in vitro adult immersion test (AIT), and the egg hatch test (EHT) in all eight populations. The larval packet test (LPT) was used on PR6 and PRA tick populations. The treatment groups were composed of G1: dichlorvos 45% plus cypermethrin 5%, G2: deltamethrin 2.5%, G3: cypermethrin 15%, chlorpyriphos 25%, plus citronellal 1%, and G4: amitraz 12.5%. The efficacy at PR1 to PR6 revealed that G3 and G4 achieved moderate to high efficacy, from 75.0 to 100.0% and 73 to 98%, respectively. In the LPT, the efficacy at PR6 was 76.0, 67.0, 93.0 and 30.6%, while PRA presented 100.0, 100.0, 100.0, and 54.0%, for G1, G2, G3 and G4, respectively. Sustainable parasite control strategies are discussed.(AU)

O controle do carrapato representa um grande desafio na saúde animal. O objetivo deste trabalho foi avaliar a eficácia de compostos acaricidas contra Rhipicephalus microplus em sistemas de pecuária leiteira no Paraná, Brasil. Foram selecionadas seis fazendas (PR1-PR6), onde são aplicados produtos carrapaticidas regularmente. Duas outras fazendas que adotaram protocolos alternativos, PRS (tratamento seletivo) e PRA (controle agroecológico individual), também foram incluídas nos testes. R. microplus ingurgitadas foram coletados para testes in vitro de imersão em adultos (TIA) e teste de eclosão de ovos (TEO) em todas as oito populações. O teste de envelope de larvas (TEL) foi utilizado nas populações PR6 e PRA. Os grupos de tratamento foram compostos por G1: diclorvos 45% mais cipermetrina 5%, G2: deltametrina 2,5%, G3: cipermetrina 15%, clorpirifos 25% e mais citronelal 1% e G4: amitraz 12,5%. A eficácia em PR1 a PR6 revelou que G3 e G4 obtiveram eficácia de moderada a alta, variando de 75,0% a 100,0% e 73% a 98%, respectivamente. No TEL, a eficácia em PR6 foi de 76,0%, 67,0%, 93,0% e 30,6%, enquanto em PRA apresentou 100,0%, 100,0%, 100,0% e 54,0%, para G1, G2, G3 e G4, respectivamente. Estratégias sustentáveis de controle são discutidas neste documento.(AU)

Selective control of Rhipicephalus microplus in a dairy cattle herd from different genetic groups / Controle seletivo de Rhipicephalus microplus em rebanho leiteiro de diferentes grupos genéticos

Alternatives for Rhipicephalus microplus control are needed in the light of its resistance to acaricides. One of the ways to decrease the use of acaricides in a herd is selective control (SC). In the present study, SC was evaluated in a dairy herd consisting of different genetic groups: Holstein, Jersey, crossbreed and Girolando. Ticks were counted in the right anterior third region on around 90 cows, totaling nine evaluations at intervals of 21 days. Commercial pour-on acaricide was applied only when the infestation was greater than or equal to eight ticks larger than 4 mm in the anterior third region. Tick counts were transformed into log10 and analyzed using mixed models. There was significant difference among groups: Holstein had the highest averages of tick numbers, as expected, although 34.3% did not receive tick treatment. In the other groups, SC reduced the use of acaricides by 79.1% for crossbreed, 81.5% for Jersey and 94.9% for Girolando. The criterion used for applying the acaricide successfully kept the tick population under control. The great advantage of SC was savings to the system, without harming the animals, in addition to generate fewer residues in the animals and in the environment.(AU)

A resistência de Rhipicephalus microplus a carrapaticidas gera a necessidade de alternativas de controle. Uma das formas de diminuir o uso de carrapaticida em um rebanho é o controle seletivo do carrapato (CS). O presente estudo avaliou o CS em rebanho leiteiro, constituído de diferentes grupos genéticos: Holandês, Jersey, mestiço e Girolando. Carrapatos foram contados na região do terço anterior direito, totalizando nove avaliações em cerca de 90 vacas, a intervalos ao redor de 21 dias. Carrapaticida comercial pour-on foi aplicado somente quando a infestação fosse igual ou superior a oito carrapatos maiores que 4 mm na região anterior. Dados de contagens foram transformados em log10 e analisados por meio de modelos mistos. Houve diferença significativa entre os grupos genéticos: vacas Holandesas apresentaram maiores médias no número de carrapatos, como esperado, embora 34,3% não tenha recebido tratamento carrapaticida; nas demais, o CS proporcionou diminuição do uso de carrapaticidas de 79,1% para as mestiças, 81,5% para as Jersey e 94,9% para as Girolando. O critério utilizado para aplicar o carrapaticida manteve a população de carrapatos sob controle. A grande vantagem do CS foi a economia ao sistema, sem prejudicar os animais, com menos resíduos para animais e meio ambiente.(AU)

Eficiência de acaricidas comerciais sobre o Rhipicephalus (Boophilus) microplus de uma propriedade rural do município de Vazante, MG, Brasil / Efficiency of commercial acaricides on Rhipicephalus (Boophilus) microplus from a rural property in the city of Vazante, MG

Os carrapatos são os ectoparasitos que causam maiores prejuízos para a produção de bovinos, e em particular o Rhipicephalus (Boophilus) microplus é responsável por graves prejuízos para os produtores de carne e leite, e seu controle vem sendo dificultado pela resistência desses ácaros de pequeno porte aos carrapaticidas comerciais. O objetivo do presente trabalho foi avaliar a eficiência in vitro de 08 (oito) bases químicas presentes nos principais acaricidas do mercado, sobre o Rhipicephalus (Boophilus) microplus. Para tanto, amostras de carrapatos foram coletadas de uma propriedade rural do município de Vazante, MG, para a realização do teste de imersão de teleóginas (biocarrapaticidograma). As associações das bases químicas Cipermetrina 20% + Clorpirifós 50%; Cirpemetrina 15% + Clorpirifós 30% + Fention 15%; Cipermetrina 15% + Clorpirifós 25% + Butóxido de Piperonila 15%+ Citronela 1% e Clorpirifós 50% + Cipermetrina 6%, apresentaram eficiência de 100% no teste in vitro. Entretanto, Diclorvós 50% + Clorpirifós 20%; Supona 50%; Amitraz 12,5% e a Deltametrina 25% apresentaram eficiência menor que 95%. Os resultados obtidos sugerem uma relação direta entre produtos presentes no mercado versus resistência do Rhipicephalus (Boophilus) microplus, enfatizando a necessidade do monitoramento dos mecanismos de resistência associado à implementação de um programa de controle estratégico de carrapatos, levando ao manejo adequado de acaricidas e uma política de fiscalização atuante por parte dos órgãos competentes com relação aos produtos químicos disponíveis no mercado para o controle do Rhipicephalus (Boophilus) microplus.(AU)

Ticks are the ectoparasites that cause greater damage to the production of cattle, and in particular Rhipicephalus (Boophilus) microplus is responsible for serious damage to meat and milk producers, and its control has been hampered by the resistance of these mites. small scale to commercial ticks. The objective of the present work was to evaluate the in vitro efficiency of 08 (eight) chemical bases present in the main acaricides in the market, on Rhipicephalus (Boophilus) microplus. For that, samples of ticks were collected from a rural property in the municipality of Vazante, MG., Brazil, to perform the teleogener immersion test (biocarrapaticidogram). The associations of the chemical bases Cypermethrin 20% + Chlorpyrifos 50%; Cirpemetrina 15% + Chlorpyrifos 30% + Fention 15%; Cypermethrin 15% + Chlorpyrifos 25% + Piperonyl Butoxide 15% + Citronella 1% and Chlorpyrifos 50% + Cypermethrin 6%, showed 100% efficiency in the in vitro test. However, Dichlorvós 50% + Chlorpyrifos 20%; Suppose 50%; Amitraz 12.5% and Deltamethrin 25% showed efficiency less than 95%. The results obtained suggest a direct relationship between products present in the market versus resistance of Rhipicephalus (Boophilus) microplus, emphasizing the need to monitor resistance mechanisms associated with the implementation of a strategic tick control program, leading to the appropriate management of mites and a active inspection policy by the competent bodies regarding the chemicals available on the market for the control of Rhipicephalus (Boophilus) microplus.(AU)

Isolation and amplification of Anaplasma marginale in chicken embryo fibroblast cell culture / Isolamento e amplificação de Anaplasma marginale em cultivos celulares de fibroblastos de embriões de galinhas

Anaplasma marginale (A. marginale) is a worldwide pathogen that infects a variety of ruminants, but mostly cattle. The present study aimed to describe an isolation technique for A. marginale, using chicken embryo Þ broblast (CEF) cell culture. Blood and tick samples were collected from 5 calves from 2 to 3 months old, which were considered to be infected with A.marginale due to anemia, jaundiced mucous membranes, and prostration. DNA extraction and PCR were performed for diagnosis using blood and tick samples. All tick and blood samples tested positive in PCR. Additionally, ticks were crushed with the aid of a blender for inoculation in CEF cell culture. After inoculation, the cultures were kept at 37ºC and 5% CO2 for 15 days. The cell supernatant of cell cultures was again analyzed using PCR and Wright stain method to conÞ rm A. marginale isolation. Cell cultures tested positive in PCR, and the presence of the agent was demonstrated by Wright stain. Therefore, by using CEF cell culture it was possible to isolate and amplify the A. marginale in a concentration of 1.3 x 107.2 bodies per mL. The CEF cells are undemanding and easy to preserve; they are an option for isolation and production of A. marginale under laboratory conditions.(AU)

Anaplasma marginale (A. marginale) é um patógeno mundial que infecta uma variedade de ruminantes, mas principalmente bovinos. O presente estudo teve como objetivo descrever uma técnica de isolamento para A. marginale, utilizando cultivo celular de Þ broblastos de embriões (CFE) de galinhas. Para isso, foram coletadas amostras de sangue e de carrapatos de 5 bezerros, entre 2 e 3 meses de idade, os quais, devido a anemia, icterícia de mucosas e prostração, foram considerados supostamente infectados com A. marginale. Ethics Approval This study was approved by Credenciamento Institucional para Atividades com Animais em Ensino ou Pesquisa (CIAEP: 02.0420.2021). Consent to participate Not applicable Consent to publish Not applicable Data availability Not applicable Para o diagnóstico, realizaram-se extração de DNA e posterior PCR a partir das amostras de sangue e de carrapatos coletados. Todos os carrapatos e amostras de sangue foram positivas para o teste de PCR. Além disso, os carrapatos foram triturados com o auxílio de um liquidiÞ cador para inoculação em CFE. Após a inoculação, as culturas foram mantidas a 37ºC e a 5% de CO2 durante 15 dias. O sobrenadante celular das culturas foi novamente analisado por PCR e pela técnica de coloração de Wright para conÞ rmar o isolamento de Anaplasma marginale. As culturas celulares foram po sitivas por PCR, e a presença do agente foi comprovada por meio da coloração de Wright. Portanto, utilizando CFE, foi possível isolar e ampliÞ car o A. marginale em uma concentração de 1,3x107,2 bactérias por ml. As células da CEF são pouco exigentes, de fácil manutenção e uma boa opção para isolamento e produção de A. marginale em condição laboratorial.(AU)

Hemoperitoneum in a cow with lumbar muscle hemangiosarcoma

Background: Hemangiosarcoma is a malignant neoplasm of endothelial cells with an infiltrative growth pattern. Hemangiosarcomas are frequently reported in canines and rare in felines, sheep, goats, swine, horses and cattle. Few cases of hemangiosarcoma were reported in cattle. In the present report, we describe the clinicopathological findings of a bovine muscle hemangiosarcoma. Case: A 6-year-old, Girolando cow from the Dairy Cattle Sector of the Federal Rural University of Rio de Janeiro (UFRRJ), Seropédica, presented sternal decubitus. Clinical signs were markedly pale mucous membranes, moderate dehydration, respiratory distress, and increased heart rate. The hematological examination revealed intense regenerative anemia. Due to the worsening of the clinical condition, the cow was submitted to euthanasia. The necropsy and collection of various fragments of organs were performed, which were sent to the "Setor de Anatomia Patológica" (SAP-UFRRJ). Tissues were fixed in 10 % buffered formalin, routinely processed for histology and stained with Hematoxylin and Eosin (HE). The external mucous membranes were markedly pale. Multifocal areas of 1.5 x 1.0 cm, irregular and dark red were observed dissecting the quadratus lumborum muscle (hemangiosarcoma) fibers. These neoplasms were associated with an extensive cruoric clot adhered to the muscle fibers. The extensive, red, friable mass measured approximately 76 x 55 x 20 cm on the serous surfaces of the organs of the peritoneal cavity (hemoperitoneum). The spleen was moderately reduced. The bone marrow was markedly pale. Histologically, it was observed that there was an extensive proliferation of endothelial cells in the quadratus lumbar muscle mass dissecting the epimysium and perimysium. Endothelial cells had moderate pleomorphism, organized in vascular channels and forming multifocally solid areas with a significant amount of eosinophilic fibrillar material (fibrin). Sections of muscle neoplasm were subjected to immunohistochemistry with anti-von Willebrand factor primary antibody, which showed a multifocal moderate cytoplasmic immunolabeling of neoplastic endothelial cells. Discussion: There are few reports of striated muscle hemangiosarcoma in cattle. Muscular hemangiosarcomas were reported in a 4-month-old calf in the left cervical trapezius muscle and a 6-year-old Holstein cow with left pelvic limb mass lateral and distal to the knee. Some reports presented hemangiosarcoma in the iliopsoas muscle, left cervical trapezius muscle, pelvic limb muscles and right cervical muscle of the bovine. In the presented report, hemoperitoneum occurred as a result of hemorrhages from muscle hemangiosarcoma. Other studies have demonstrated cavity hemorrhages in joint, pelvic, pleural and cranial cavities associated with hemangiosarcoma. Hemangiosarcoma with regenerative anemia must be distinguished from other diseases that cause anemia. The main differential diagnoses of bovine with anemia are vena cava syndrome, coumarin derivatives poisoning, acute poisoning by Pteridium spp., tick fever, anaplasmosis, babesiosis and trypanosomiasis. Hemangiosarcoma should be differentiated from other lesions as hemangioma, vascular tumor of lymphatic endothelium and perivascular wall tumors. Cases with poorly differentiated morphology should be submitted for immunohistochemistry. In the present hemangiosarcoma case, we have used the von Willebrand factor for immunohistochemistry diagnosis. Expression of angiogenic growth factors such as CD31, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and angiopoietin-1 (Ang-1) have also been used in the diagnosis of vascular proliferation lesions. Hemangiosarcoma in cattle should be included mainly in the differential diagnosis of diseases that cause acute anemia in cattle.

Babesia bovis in large ruminants in Pakistan - molecular detection and haemato-biochemical alterations

Background: Babesiosis is endemic in Pakistan and is one of the most important bovine diseases that causes huge economic losses and high mortality in young animals. A hematobiochemical study was conducted to unveil the difference between diseased and healthy animals in selected districts i.e., Faisalabad (31° 25' 7.3740'' N and 73° 4' 44.7924'' E), Toba Tek Singh (30° 58' 9.7392'' N and 72° 27' 40.7484'' E) and Jhang (31° 16' 40.9656'' N and 72° 18' 42.3360'' E) of Punjab, Pakistan. Materials, Methods & Results: A total of 518 (Cattle = 360, Buffalo = 158) blood samples were collected. The samples were analyzed by polymerase chain reaction (PCR) targeting apocytochrome b-gene (Babesia bovis-gene) (CYTb) followed by haemato-biochemical analysis. Chi-square test for univariate analysis was used to analyze the data. In summer the PCR-based prevalence was 29.4 (53/180) and 24.05% (19/79) in cows and buffaloes, respectively. On the other hand, in winter results showed that 12.7 (23/180), 13.92 % (11/79) samples positive for Babesia genus from cows and buffaloes, respectively. The positive samples were further investigated for hematological and biochemical analysis. The results revealed that, the mean value of hematological parameters like RBCs, Hb, PCV, MCV and MCHC was significantly (P < 0.05) decreased in infected animals (cows and buffaloes) as compared to the non-infected ones. While the biochemical parameters like Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), cholesterol and Lactate dehydrogenase were significantly (P < 0.05) increased in infected animals as compared to healthy animals. This study is the first molecular and hematobiochemical evidence of Babesia bovis in dairy herds of Punjab province, Pakistan. Discussion: Bovine babesiosis is one of the important tick-borne diseases (TBD) affecting dairy industry. In bovines, among 3 Babesia species that cause the disease B. bovis is more pathogenic with high mortality and morbidity. Pakistan is situated in tropical and sub-tropical region where the humidity is high in some part of countries. This high humidity mostly favors the reproduction of the ticks thus higher prevalence of TBDs in this region. Initially the babesiosis was diagnosed by light microscopy using thin blood smear stained with Giemsa stain. Many studies verified that PCR is a more specific and sensitive tool than conventional techniques for the detection of carrier / asymptomatic ruminants. The haemato-biochemical profile is another valuable footprint to track the disease. Keeping in view the above-mentioned fact the present project has been planned to evaluate the haemato-biochemical alteration between health and Babesia infected cattle along with the molecular detection of Babesia species involved in bovine babesiosis. The mean values of haematobiochemical parameters in clinically ill and healthy animals revealed that the mean values of hematological parameters like RBCs, Hb, PCV, and HCT were significantly decreased in diseased animals as compared to the healthy ones. All these might be due the fact that the parasite is intra-erythrocytic in nature and destruction of red blood cells results in significant (P < 0.05) decrease level of all the hematological parameters. The mean value of ALT in babesiosis infected cattle was significantly higher as compared to healthy cattle. The mean values of AST and LDH in babesiosis infected cows was significantly higher as compared to that in healthy cows. The elevation in liver enzymes in babesiosis may be due to the hepatic damage and lesions induced by the parasite during its multiplication in the blood followed by disturbed liver function. These enzymes are present in high concentrations in the muscles and liver. High level of these enzymes in the blood is indicator of organ necrosis or damage.

An atypical case of Babesia bigemina parasitising a dog from a rural area of eastern Mexico / Um caso atípico de Babesia bigemina parasitando um cão de uma área rural do leste do México

A dog that shared habitat with domestic animals in a cattle farm and that was exposed to wildlife was taken to a private practitioner for clinical examination. The analyses conducted on the patient revealed the presence of Babesia bigemina by a molecular test. Clinical signs such as lethargy, anorexia and hyperthermia > 39 °C, pale mucous membranes and blood urine were observed in the patient. The animal was treated with imidocarb dipropionate (two doses each 0.5 ml/10 kg b.w. at an interval of 14 days). On treatment day 7, the clinical signs were mostly reduced. On day 30, PCR was carried out to assess the efficacy of the treatment, with a negative result. This case represents the first report of babesiosis due to B. bigemina in a dog living on a cattle farm in Mexico. It indicates the lower host specify of these pathogens and that dogs can play a role as sentinels of vector-borne parasites in livestock animals.(AU)

Um cão que compartilhava hábitat com animais domésticos em uma fazenda de gado e que foi exposto à vida selvagem foi levado a um clínico particular para que fosse examinado. As análises realizadas no paciente revelaram a presença de Babesia bigemina por um teste molecular. Sinais clínicos, como letargia, anorexia e hipertermia > 39°C, mucosas pálidas e sangue na urina foram observados no paciente. O animal foi tratado com dipropionato de imidocarb (duas doses cada 0,5 ml/10 kg de peso corporal em um intervalo de 14 dias). No dia de tratamento 7, os sinais clínicos foram reduzidos. No dia 30, foi realizada PCR para avaliar a eficácia do tratamento, com resultado negativo. Esse caso representa o primeiro relato de babesiose por B. bigemina em um cão que vive em uma fazenda de gado no México. Isso indica que o hospedeiro inferior especifica esses patógenos, e que os cães podem desempenhar um papel como sentinelas de parasitas transmitidos por vetores em animais de criação.(AU)

Genetic and environmental factors that affect tick infestation in Nelore x Angus crossbreed cattle / Fatores genéticos e ambientais que afetam a infestação de carrapatos em bovinos cruzados Nelore x Angus

This study evaluated the effects of seasons and latitude on tick counting and determined the best model to estimate genetic parameters for tick count and hair coat. Records of animals naturally exposed to ticks on farms in several Brazilian states and in Paraguay were used. The ANOVA was used to verify the effects of seasons and latitude on the tick count trait. Spring was the season with the highest average, followed by summer and autumn, which showed no differences between them. The winter presented the lowest average values. Latitude -11° had the highest mean value followed by latitude -18°. The Bayesian approach was used to evaluate tick count and hair coat and to identify a suitable model for estimating genetic parameters for use in genetic evaluations. The data were analyzed using an animal model with four different specifications for “fixed” purposes. The inference was based on a Markov chain Monte Carlo (MCMC). The criteria for selection of the Bayesian model indicated that the M1 model, which considered the breed composition in the contemporary group, was superior to the other models, both for tick count and hair coat. Heritability estimates for tick count and hair coat obtained using the M1 model were 0.14 and 0.22, respectively. The rank correlations between the models for tick count and hair coat were estimated and reordering was verified for tick count. The estimated genetic correlation between tick count and hair coat traits was negative (-0.12). These findings suggest that different genes regulate tick count and hair coat.

Os objetivos foram avaliar os efeitos das estações e latitude na contagem de carrapatos e determinar o melhor modelo para estimar parâmetros genéticos para contagem de carrapatos e pelame. Foram utilizados registros de animais expostos naturalmente a carrapatos em fazendas em vários estados brasileiros e no Paraguai. A ANOVA foi utilizada para verificar os efeitos das estações e da latitude na característica de contagem de carrapatos. A primavera foi a estação com a maior média, seguida pelo verão e outono, que não mostraram diferenças entre eles. O inverno apresentou os menores valores médios. A latitude -11° teve o maior valor médio seguido pela latitude -18°. A abordagem bayesiana foi usada para avaliar a contagem de carrapatos e o pelame e identificar o modelo adequado para estimar parâmetros genéticos e para uso em avaliações genéticas. Os dados foram analisados usando um modelo animal com quatro especificações diferentes para efeitos “fixos”. A inferência foi baseada em uma cadeia de Markov Monte Carlo (MCMC). Os critérios de seleção do modelo bayesiano indicaram que o modelo M1, que considerou a composição racial no grupo contemporâneo, foi superior aos demais modelos, tanto na contagem de carrapatos e para pelame. As estimativas de herdabilidade para contagem de carrapatos e pelame obtidas usando o modelo M1 foram de 0,14 e 0,22, respectivamente. As correlações de ranking entre os modelos para a contagem de carrapatos e pelame foram estimadas e a reordenação foi verificada para a contagem de carrapatos. A correlação genética estimada entre a contagem de carrapatos e pelame foi negativa (-0,12). Esses achados sugerem que genes diferentes regulam a contagem de carrapatos e pelame.

Genetic and environmental factors that affect tick infestation in Nelore x Angus crossbreed cattle / Fatores genéticos e ambientais que afetam a infestação de carrapatos em bovinos cruzados Nelore x Angus

This study evaluated the effects of seasons and latitude on tick counting and determined the best model to estimate genetic parameters for tick count and hair coat. Records of animals naturally exposed to ticks on farms in several Brazilian states and in Paraguay were used. The ANOVA was used to verify the effects of seasons and latitude on the tick count trait. Spring was the season with the highest average, followed by summer and autumn, which showed no differences between them. The winter presented the lowest average values. Latitude -11° had the highest mean value followed by latitude -18°. The Bayesian approach was used to evaluate tick count and hair coat and to identify a suitable model for estimating genetic parameters for use in genetic evaluations. The data were analyzed using an animal model with four different specifications for “fixed” purposes. The inference was based on a Markov chain Monte Carlo (MCMC). The criteria for selection of the Bayesian model indicated that the M1 model, which considered the breed composition in the contemporary group, was superior to the other models, both for tick count and hair coat. Heritability estimates for tick count and hair coat obtained using the M1 model were 0.14 and 0.22, respectively. The rank correlations between the models for tick count and hair coat were estimated and reordering was verified for tick count. The estimated genetic correlation between tick count and hair coat traits was negative (-0.12). These findings suggest that different genes regulate tick count and hair coat.(AU)

Os objetivos foram avaliar os efeitos das estações e latitude na contagem de carrapatos e determinar o melhor modelo para estimar parâmetros genéticos para contagem de carrapatos e pelame. Foram utilizados registros de animais expostos naturalmente a carrapatos em fazendas em vários estados brasileiros e no Paraguai. A ANOVA foi utilizada para verificar os efeitos das estações e da latitude na característica de contagem de carrapatos. A primavera foi a estação com a maior média, seguida pelo verão e outono, que não mostraram diferenças entre eles. O inverno apresentou os menores valores médios. A latitude -11° teve o maior valor médio seguido pela latitude -18°. A abordagem bayesiana foi usada para avaliar a contagem de carrapatos e o pelame e identificar o modelo adequado para estimar parâmetros genéticos e para uso em avaliações genéticas. Os dados foram analisados usando um modelo animal com quatro especificações diferentes para efeitos “fixos”. A inferência foi baseada em uma cadeia de Markov Monte Carlo (MCMC). Os critérios de seleção do modelo bayesiano indicaram que o modelo M1, que considerou a composição racial no grupo contemporâneo, foi superior aos demais modelos, tanto na contagem de carrapatos e para pelame. As estimativas de herdabilidade para contagem de carrapatos e pelame obtidas usando o modelo M1 foram de 0,14 e 0,22, respectivamente. As correlações de ranking entre os modelos para a contagem de carrapatos e pelame foram estimadas e a reordenação foi verificada para a contagem de carrapatos. A correlação genética estimada entre a contagem de carrapatos e pelame foi negativa (-0,12). Esses achados sugerem que genes diferentes regulam a contagem de carrapatos e pelame.(AU)

Genetic evaluation models for resistance to ticks in a crossbred Angus-Nellore population / Modelos de avaliação genética para resistência a carrapatos em uma população mestiça de Angus-Nelore

This research identified the animal model that best describes the genetic and residual variations for tick counts in yearlings from a crossbred Angus-Nellore population of 6,951 animals that are progenies of 382 bulls and 6,198 cows. Genetic values were predicted by the Bayesian inference methodology. The models tested were: Traditional Animal, and Crossbred Animal with and without segregation, considering residual homoscedastic and heteroscedastic variances. The criteria of choice were the number of parameters, deviance information, and predictive order, which indicated the best fitfor the Traditional Animal model and Crossbred Animal model (with segregation), both with residual heteroscedastic Gaussian variance. The mean values of fixed genetic effects were positive and similar in the both models, indicating that animals with higher proportion of the Angus breed had greater infestation, and the Nellore breed was an important addition for resistance to ticks. The estimated genetic variation by the heteroscedastic Gaussian Animal model for the Nellore breed was 4.54-fold higher than that estimated for the Angus breed. The estimates of heritability of the different genetic groups ranged from 0.12 to 0.15 and from 0.01 to 0.35, respectively, for the Traditional Animal model and for the heteroscedastic Gaussian crossbred model. The Spearman’s rank-order correlation for the predicted genetic values was 0.94, considering all sires. However, when considering the top 10%, 20%, and 30% sires, differences in ranking were more evident (0.28 to 0.67). The Crossbred Animal model with segregation and heterogeneous residual variances was the most appropriate for genetic evaluation of tick counts on animals from Angus-Nellore crossings.

O objetivo neste trabalho foi identificar o modelo animal que melhor descreve a variação genética e residual para a característica contagem de carrapatos ao sobreano, em uma população multirracial Angus-Nelore constituída por 6.951 animais, filhos de 382 touros e 6.198 vacas. Os valores genéticos foram preditos a partir da metodologia de inferência Bayesiana utilizando os seguintes modelos: Animal Tradicional, Animal Multirracial sem e com segregação, considerando as variâncias residuais homo ou heterocedástica. Os critérios de escolha foram o Número de Parâmetros, a Informação de Deviance e a Ordenada Preditiva, os quais apontaram os Modelos Animal Tradicional e o Multirracial com Segregação, ambos com variância residual Gaussiana heterocedástica, como os de melhor ajuste. Os valores médios dos efeitos genéticos fixos foram positivos e similares nos dois modelos, sugerindo que os animais com maior proporção da raça Angus sofreram maior infestação e atribuindo-se, portanto, a raça Nelore importante papel na resistência ao carrapato. Verificou-se que a variância genética estimada pelo Modelo Animal Gaussiano heterocedástico para a raça Nelore foi 4,54 vezes maior do que a estimada para a raça Angus. As estimativas de herdabilidade nos diferentes grupos genéticos variaram de 0,12 a 0,15 e de 0,01 a 0,35, respectivamente, no Modelo Animal Tradicional e no Multirracial Gaussiano heterocedástico. A correlação de ordenamento de Spearman entre os valores genéticos preditos, considerando todos os reprodutores da população, foi 0,94. Contudo, ao considerar os melhores touros, TOP 10%, 20% e 30%, as diferenças com relação ao ordenamento foram mais evidentes (0,28 a 0,67). O modelo Animal Multirracial com Segregação com variâncias residuais heterogêneas foi o mais apropriado para avaliação genética da característica Contagem de Carrapatos de animais produtos do cruzamento Angus-Nelore.

Genetic evaluation models for resistance to ticks in a crossbred Angus-Nellore population / Modelos de avaliação genética para resistência a carrapatos em uma população mestiça de Angus-Nelore

This research identified the animal model that best describes the genetic and residual variations for tick counts in yearlings from a crossbred Angus-Nellore population of 6,951 animals that are progenies of 382 bulls and 6,198 cows. Genetic values were predicted by the Bayesian inference methodology. The models tested were: Traditional Animal, and Crossbred Animal with and without segregation, considering residual homoscedastic and heteroscedastic variances. The criteria of choice were the number of parameters, deviance information, and predictive order, which indicated the best fitfor the Traditional Animal model and Crossbred Animal model (with segregation), both with residual heteroscedastic Gaussian variance. The mean values of fixed genetic effects were positive and similar in the both models, indicating that animals with higher proportion of the Angus breed had greater infestation, and the Nellore breed was an important addition for resistance to ticks. The estimated genetic variation by the heteroscedastic Gaussian Animal model for the Nellore breed was 4.54-fold higher than that estimated for the Angus breed. The estimates of heritability of the different genetic groups ranged from 0.12 to 0.15 and from 0.01 to 0.35, respectively, for the Traditional Animal model and for the heteroscedastic Gaussian crossbred model. The Spearmans rank-order correlation for the predicted genetic values was 0.94, considering all sires. However, when considering the top 10%, 20%, and 30% sires, differences in ranking were more evident (0.28 to 0.67). The Crossbred Animal model with segregation and heterogeneous residual variances was the most appropriate for genetic evaluation of tick counts on animals from Angus-Nellore crossings.(AU)

O objetivo neste trabalho foi identificar o modelo animal que melhor descreve a variação genética e residual para a característica contagem de carrapatos ao sobreano, em uma população multirracial Angus-Nelore constituída por 6.951 animais, filhos de 382 touros e 6.198 vacas. Os valores genéticos foram preditos a partir da metodologia de inferência Bayesiana utilizando os seguintes modelos: Animal Tradicional, Animal Multirracial sem e com segregação, considerando as variâncias residuais homo ou heterocedástica. Os critérios de escolha foram o Número de Parâmetros, a Informação de Deviance e a Ordenada Preditiva, os quais apontaram os Modelos Animal Tradicional e o Multirracial com Segregação, ambos com variância residual Gaussiana heterocedástica, como os de melhor ajuste. Os valores médios dos efeitos genéticos fixos foram positivos e similares nos dois modelos, sugerindo que os animais com maior proporção da raça Angus sofreram maior infestação e atribuindo-se, portanto, a raça Nelore importante papel na resistência ao carrapato. Verificou-se que a variância genética estimada pelo Modelo Animal Gaussiano heterocedástico para a raça Nelore foi 4,54 vezes maior do que a estimada para a raça Angus. As estimativas de herdabilidade nos diferentes grupos genéticos variaram de 0,12 a 0,15 e de 0,01 a 0,35, respectivamente, no Modelo Animal Tradicional e no Multirracial Gaussiano heterocedástico. A correlação de ordenamento de Spearman entre os valores genéticos preditos, considerando todos os reprodutores da população, foi 0,94. Contudo, ao considerar os melhores touros, TOP 10%, 20% e 30%, as diferenças com relação ao ordenamento foram mais evidentes (0,28 a 0,67). O modelo Animal Multirracial com Segregação com variâncias residuais heterogêneas foi o mais apropriado para avaliação genética da característica Contagem de Carrapatos de animais produtos do cruzamento Angus-Nelore.(AU)

Use of anti-tick drugs in dairy farms in the microregion of Alfenas, Minas Gerais, Brazil / Uso de carrapaticidas em fazendas leiteiras na microrregião de Alfenas, Minas Gerais, Brasil

Abstract Ectoparasitic infestation in dairy cattle, the most common being Rhipicephalus (Boophilus) microplus, causes significant loss in production. The control of ectoparasites often occurs incorrectly, resulting in resistance to the active ingredients and residues in milk. To understand of acaricide use in the microregion of Alfenas, Minas Gerais (Brazil), questionnaires were applied to the owners of 100 dairy farms in the region and were selected randomly. Dairy farms were allocated according to production scale: up to 150 liters/day, 151-400 liters/day and more than 400 liters/day. The interviewees were asked about production characteristics, acaricide management and active ingredients. The interview answers were subjected to descriptive analysis. Results showed that all properties, independent of production-scale, used acaricides. The most cited was: Cypermethrin Chlorpyrifos Citronellal (31%), Fluazuron (18.6%) and Fipronil (17%). Among the interviewed, 41,1% use drugs that have restrictions that are not allowed in legislation for use in lactating dairy cows (fluazuron, fipronil, ivermectin). 15% affirmed they weren't aware of the "withdrawal period" of medication and 73% change in the active ingredient used. In order to revert this antiparasitic drug's resistance situation and contamination of milk with drug residues, it is necessary to focus on the awareness of milk producers and training of labor.

Resumo A infestação por ectoparasitas em bovinos leiteiros, sendo o mais comum o Rhipicephalus (Boophilus) microplus, causa prejuízos significativos na produção. No entanto, o controle dos ectoparasitas geralmente ocorre incorretamente, resultando em resistência aos princípios ativos e presença de resíduos no leite. Para entender os padrões de uso de acaricidas na microrregião de Alfenas, Minas Gerais, Brasil, foram aplicados questionários aos proprietários de 100 fazendas leiteiras que foram classificadas de acordo com uma escala de produção: até 150 litros/dia, de 151 a 400 litros/dia e mais de 400 litros/dia. Os entrevistados foram questionados sobre características da produção, manejo do acaricida de gado e conhecimento sobre os princípios ativos. Todas as propriedades, independentemente da escala de produção, usavam acaricidas. Foram citados com maior frequência: Cipermetrina + Clorpirifós + Citronelal (31%), Fluazuron (18.6%) e Fipronil (17%). Entre os produtores entrevistados, 41,1 % fazem uso de drogas com restrição que não são atualmente permitidas na legislação para uso em vacas em lactação (fluazuron, fipronil, ivermectina). 15% dos produtores de leite afirmaram não estar cientes do "período de carência" dos medicamentos; outros relatam trocas constantes do princípio ativo utilizado. Para reverter a situação do uso indiscriminado de antiparasitários, é necessário focar na conscientização dos produtores de leite e na formação do trabalho.