Tânia Regina Bettin dos Santos

Análise da eficácia de acaricidas sobre o carrapato Boophilus microplus, durante a última década, na região sul do Rio Grande do Sul

A regiao sul do Rio Grande do Sul caracteriza-se por uma bovinocultura com predominio de racas europeias, tanto para producao de carne, quanto de leite. Essa regiao e considerada area marginal de ocorrencia do carrapato Boophilus microplus, cujo parasitismo ocorre entre final de setembro e meados de maio devido as baixas temperaturas do inverno. No entanto, as perdas causadas por esse parasito sao elevadas, o que tem sido agravadas pela selecao de populacoes de carrapatos resistentes aos acaricidas. O presente trabalho teve como objetivo estudar a situacao de sensibilidade/resistencia do carrapato bovino, assim como a dinâmica de uso dos diferentes grupos acaricidas disponiveis no mercado, na regiao sul do Rio Grande do Sul, na ultima decada. Durante o periodo foram avaliadas amostras de carrapatos provenientes de 124 propriedades, de 14 municipios da regiao. Em cada propriedade foram coletadas teleoginas e informacoes relativas ao manejo. No Laboratorio de Parasitologia do Instituto de Biologia da UFPel, foi realizado teste de imersao de teleoginas. Observou-se que durante o primeiro trienio os produtos mais utilizados eram a base de piretroide, determinando uma selecao de populacoes resistentes a esse principio ativo. No terceiro trienio os produtos a base de amitraz dominaram o mercado, ocorrendo tambem selecao de populacoes resistentes. No primeiro trienio, todas as populacoes de carrapato analisadas eram sensiveis ao amitraz (indice de eficacia = 95%), enquanto que, ao final do estudo, no terceiro trienio, esse indice de eficacia foi detectado em apenas 79% das populacoes estudadas. Foram detectadas falhas de manejo na regiao, como numero de aplicacao superior a seis por ano, aplicacao de acaricida somente quando visualizadas as formas adultas e uso exclusivo de acaricidas para o controle do carrapato, que predispoem a selecao de populacoes resistentes.

Abordagem sobre o controle do carrapato Rhipicephalus (Boophilus) microplus no sul do Rio Grande do Sul

In the southern region of Rio Grande do Sul, cattle become infested with Rhipicephalus (B.) microplus mainly between October and April due to the climatic conditions. In addition to knowing its life cycle, knowledge of parasites epidemiology is essential to establish management strategies. Epidemiological studies on resistance to acaricides in Rio Grande do Sul as well as in the rest of Brazil are scarce. Moreover, the large geographical area and the structural deficiency with respect to the use and access to databases make reliable data difficult to obtain. The present study surveyed the perception by cattle breeders in the southern region of Rio Grande do Sul in regards of identification of R. (B.) microplus populations that are difficult to manage using acaricides, as well as the risk factors for the selection of resistant tick populations. Tick management data on beef cattle in 85 properties of seven municipalities were collected. The results revealed that the difficulty in tick management correlated positively with levels of education of the farm owners (up to elementary school, OR = 3.67 and p = 0.01) and with the yearly number of acaricide applications (over four, with OR = 4.05 and p= 0.006). These results also suggest that properties with more than 100 beef cattle under extensive farming conditions in the southern region of Rio Grande do Sul show characteristics that may contribute to longer acaricide lifetimes as compared to other regions in the Country.

Comparison of three larval bioassays to evaluate susceptibility of Rhipicephalus (Boophilus) microplus to amitraz

Field samples of Rhipicephalus (Boophilus) microplus from the state of Rio Grande do Sul, Brazil, were assessed using the following methods: larval packet test (LPT), larval immersion test (LIT) and syringe immersion test (SIT). The following parameters were determined for each population and for the Mozo susceptible reference strain: lethal concentration for 50% (LC50) with its 95% confidence interval (95% CI), regression line slope and resistance ratio (RR). Using the LPT, only one population was susceptible to amitraz, presenting a RR of 1.9. Using the same technique, the other populations presented RRs of between 92.9 and 3445.8 and were considered resistant. The LC50 of the Mozo strain calculated using the LPT, LIT and SIT was 2.9, 27.3, and 52.7 µg/mL, respectively. In general, a good fit to the probit statistical model was only achieved using the LPT. The results obtained in this study impair recommendations for using the LIT and SIT to diagnose amitraz resistance in R. (B.) microplus populations. Additional studies are required to improve the sensitivity of these tests in relation to the LPT.

Parâmetros da fase de vida livre de Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae): adaptado ao clima subtropical

Rhipicephalus sanguineus e considerada a especie de ixodideo mais prevalente no mundo e foi introduzida no meio urbano pelo cao domestico, seu principal hospedeiro. O presente estudo teve por objetivo conhecer o desempenho biologico da fase de vida livre de R. sanguineus, adaptado a regiao Sul do Rio Grande do Sul, por meio da estimativa de parâmetros biologicos, sob condicoes controladas de temperatura (27 ± 1°C) e umidade relativa (> 70,0%). Foram coletadas teleoginas pre e pos-desprendimento dos caes hospedeiros, sendo cada grupo experimental constituido de 200 teleoginas. Verificou-se que a massa media de cada teleogina foi de 170 mg, o periodo de pre-postura de quatro dias, a massa total de ovos de 100 mg, a massa da quenogina de 30 mg e a longevidade larval de 31 dias, com indices de eficacia reprodutiva e nutricional de 61,0 e 74,0%, respectivamente. Quanto a dinâmica de postura, 98,5% foram ovipostos na primeira semana de incubacao e a eclodibilidade foi de 94,5%. A analise dos parâmetros biologicos de R. sanguineus revelou que nao houve diferenca estatistica (p > 0,05) entre as femeas coletadas diretamente do corpo do hospedeiro e aquelas provenientes do ambiente. Os dados biologicos observados em R. sanguineus adaptados as condicoes climaticas do Sul do Rio Grande do Sul sao similares aos de outras regioes do Brasil. Alem disso, as coletas de R. sanguineus para estudos epidemiologicos podem ser realizadas tanto do ambiente quanto do corpo do hospedeiro, devido a similaridade que ambos os grupos apresentam em seus parâmetros biologicos.

Avaliação da eficácia de produtos isoterápicos no controle de Rhipicephalus (Boophilus) microplus

The Rhipicephalus (Boophilus)microplus is responsible for considerable losses in Brazilian cattle. The control of such parasites has been done mainly with the use of acaricides, and the isopathy is an alternative. The objective of this work is to analyze the efficiency of the use of isopathy as an alternative tool to control the cattle tick. We used 18 cows of the European race, kept in extensive livestock system in the municipality of Cangucu, Rio Grande do Sul, Brazil. The animals were divided into control group (Lot A) and group treated with isopathy (Lot B). Mineral salt was used as a vehicle for the administration of isopathy, Lot A received mineral salt with placebo (sugar) and Lot B received mineral salt with isopathy. The animals were artificially infested with 10 thousan larvae of R. (B.)microplus , and in the days 20, 21 and 22 post-infestation engorged females were counted and collected. The ticks from each batch were randomly divided into nine groups of ten subjects each for analysis of biological parameters and subsequent calculation of the Nutritional Index and the Effectiveness Reproductive Index. For comparison of average engorged females from each group were employed ANOVA and LSD Test. The animals treated with isopathy showed a 53.4% reduction in the average number of ticks when compared with the untreated group (p = 0.001). As for biological standards, there was no statistical difference. It is concluded that the use of isopathy was able to reduce infestation of R. (B.)microplus , showing up as a promising alternative to control this ticks.