Acaricidal efficacy of fluralaner against Rhipicephalus microplus ticks under laboratory and field conditions in Brazil.

IF 3 2区医学 Q1 PARASITOLOGY

Parasites & Vectors Pub Date : 2025-04-28 DOI:10.1186/s13071-025-06775-2

Daniel de Castro Rodrigues, Gabriel Webert Gomes, Francisca Leticia Vale, Ana Lúcia Coutinho Teixeira, Isabela Santos Silva, Haile Dean Figueiredo Chagas, Tom Strydom, Siddartha Torres, Rafael Paranhos de Mendonça, Fernando de Almeida Borges, Lívio Costa Junior, Lorena Lopes Ferreira, Welber Daniel Zanetti Lopes, Caio Monteiro

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引用次数: 0

Abstract

Background: The first isoxazoline-based acaricide (fluralaner) for the control of Rhipicephalus microplus was introduced onto the market in 2022, initially in Brazil, followed by other Latin American countries. Therefore, it is important to establish laboratory methods to monitor the susceptibility of populations of R. microplus to this molecule and to determine the relationship between the results of laboratory tests and those from field trials.

Methods: A larval immersion test (LIT) was performed on 18 populations of R. microplus. The lethal concentration 50 (concentration causing 50% mortality [LC50]) values were calculated to determine the resistance ratios (RRs) of the populations. The lethal concentration 99 (concentration causing 99% mortality [LC99]) values were calculated to determine the discriminating doses (DDs = 2 × LC99). The DDs were applied in tests with the POA (susceptible) and GYN (resistant) strains, as well as in tests with the population that presented the lowest LC50 value (population 14) and with the two populations that presented the highest LC50 value (populations 10 and 16). Finally, we performed field trials with the population that presented the lowest and two highest LC50 values.

Results: In the LIT with fluralaner, the LC50 values ranged from 0.144 to 0.481 µg/mL for the 18 R. microplus populations. The mortality rate was 100% in the tests of the DDs in the five populations tested. In the field trials, the efficacy of fluralaner was similar for the three populations of R. microplus tested (populations 14, 10 and 16), with therapeutic efficacy (until day 21) of 100% and persistent efficacy (between days 28 and 42) > 95%.

Conclusion: We observed natural variability in the susceptibility of larvae from the different populations of R. microplus that had never been treated with this compound. Despite the observed variability in the in vitro results (LC50), a comparable efficacy of > 90% lasting until day 42 was observed in the field trials. Also, based on the results of the laboratory testing (LC50 and DD) and field trials, we can conclude that there was no resistance to fluralaner in the 18 studied tick populations.

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氟拉烷对巴西小头蜱的室内和田间杀螨效果研究。

背景：第一种以异恶唑啉为基础的杀螨剂氟拉烷（fluralaner）于2022年投放市场，最初在巴西投放，随后在其他拉美国家投放。因此，有必要建立实验室方法来监测微孢子虫种群对该分子的敏感性，并确定实验室试验结果与田间试验结果之间的关系。方法：对18个小褐家鼠种群进行幼虫浸泡试验。计算致死浓度50（致死率50%的浓度[LC50]）值，确定各种群的抗性比。计算致死浓度99（致99%死亡率的浓度[LC99]）值，确定鉴别剂量（ddds = 2 × LC99）。将DDs应用于POA（易感）和GYN（耐药）菌株的试验，以及LC50值最低的群体（14群体）和LC50值最高的两个群体（10和16群体）的试验。最后，我们对LC50值最低和两个最高的种群进行了现场试验。结果：加氟拉烷后，18个小黄鼠种群的LC50值为0.144 ~ 0.481µg/mL。在对5个受测人群进行的dd测试中，死亡率为100%。在田间试验中，氟拉烷对3个种群（种群14、10和16）的治疗效果相似，治疗效果（至21天）为100%，持续效果（28 - 42天）为95%。结论：未施用该化合物的不同种群的小褐家鼠幼虫对该化合物的敏感性存在自然差异。尽管在体外结果（LC50）中观察到可变性，但在田间试验中观察到持续到第42天的> 90%的相当疗效。同时，根据实验室LC50和DD检测结果和现场试验结果，18个蜱类对氟拉烷无抗性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Parasites & Vectors 医学-寄生虫学

CiteScore

6.30

自引率

9.40%

发文量

433

审稿时长

1.4 months

期刊介绍： Parasites & Vectors is an open access, peer-reviewed online journal dealing with the biology of parasites, parasitic diseases, intermediate hosts, vectors and vector-borne pathogens. Manuscripts published in this journal will be available to all worldwide, with no barriers to access, immediately following acceptance. However, authors retain the copyright of their material and may use it, or distribute it, as they wish. Manuscripts on all aspects of the basic and applied biology of parasites, intermediate hosts, vectors and vector-borne pathogens will be considered. In addition to the traditional and well-established areas of science in these fields, we also aim to provide a vehicle for publication of the rapidly developing resources and technology in parasite, intermediate host and vector genomics and their impacts on biological research. We are able to publish large datasets and extensive results, frequently associated with genomic and post-genomic technologies, which are not readily accommodated in traditional journals. Manuscripts addressing broader issues, for example economics, social sciences and global climate change in relation to parasites, vectors and disease control, are also welcomed.