Meiring Christina, Labuschagne Michel
Clinglobal, Tamarin, Mauritius.
Clinomics, Bloemfontein, South Africa.
PLoS One. 2024 Dec 5;19(12):e0312074. doi: 10.1371/journal.pone.0312074. eCollection 2024.
Globally, the prevalence of Rhipicephalus microplus resistance to various acaricides has increased, and there is a need for the identification of molecular markers that can predict phenotypic resistance. These markers could serve as alternatives to the larval packet test (LPT), enabling rapid and accurate monitoring of resistance in these ticks against multiple acaricides. However, many of the historically identified markers are present in isolates from specific countries and their role in acaricide resistance remains unclear. This study aimed to assess these mutations by sequencing genomic regions encoding proteins historically associated with acaricide target site insensitivity and increased acaricide detoxification and comparing resistant and susceptible isolates from eight different countries. Employing a novel multiplex PCR setup developed during the study, the coding regions of 11 acaricide-resistant targets were amplified and sequenced across 37 R. microplus isolates from different locations. The identified mutations, both previously reported and novel, were compared between acaricide-susceptible and acaricide-resistant isolates, phenotypically characterized using the larval packet test or larval immersion test across five acaricide classes. Genotypes were then correlated with available phenotypes, and protein modelling of novel nonsynonymous mutations was conducted to assess their potential impact on acaricide resistance. Previously reported resistance-associated mutations were detected, some of which were present in both resistant and susceptible isolates. Novel mutations emerged from the 11 targets, but distinctions between susceptible and resistant isolates were not evident, except for the prevalent kdr mutation in synthetic pyrethroid-resistant isolates. The quest for predictive molecular markers for monitoring acaricide resistance remains challenging. Nevertheless, by utilizing a representative group of isolates, we determined that several historical mutations were present in both resistant and susceptible isolates. Additionally, the study provides valuable genetic data on acaricide-resistant and susceptible isolates from different geographical regions, focusing on genomic regions implicated in resistance. This baseline data offers a critical foundation for further research and the identification of more reliable molecular markers.
在全球范围内，微小牛蜱对各种杀螨剂的抗性流行率有所上升，因此需要鉴定能够预测表型抗性的分子标记。这些标记可作为幼虫分组试验（LPT）的替代方法，从而能够快速、准确地监测这些蜱对多种杀螨剂的抗性。然而，许多历史上鉴定出的标记存在于特定国家的分离株中，它们在杀螨剂抗性中的作用仍不明确。本研究旨在通过对编码与杀螨剂靶标位点不敏感和杀螨剂解毒增加相关的蛋白质的基因组区域进行测序，并比较来自八个不同国家的抗性和敏感分离株，来评估这些突变。利用研究期间开发的一种新型多重PCR设置，对11个抗杀螨剂靶标的编码区域进行了扩增，并对来自不同地点的37株微小牛蜱分离株进行了测序。在杀螨剂敏感和抗性分离株之间比较了已报道的和新发现的突变，这些分离株通过幼虫分组试验或幼虫浸液试验对五种杀螨剂类别进行了表型鉴定。然后将基因型与可用表型进行关联，并对新的非同义突变进行蛋白质建模，以评估它们对杀螨剂抗性的潜在影响。检测到了先前报道的与抗性相关的突变，其中一些在抗性和敏感分离株中均有出现。从11个靶标中出现了新的突变，但除了合成拟除虫菊酯抗性分离株中普遍存在的kdr突变外，敏感和抗性分离株之间的差异并不明显。寻找用于监测杀螨剂抗性的预测性分子标记仍然具有挑战性。然而，通过使用一组具有代表性的分离株，我们确定抗性和敏感分离株中都存在一些历史突变。此外，该研究提供了来自不同地理区域的抗杀螨剂和敏感分离株的有价值的遗传数据，重点关注与抗性相关的基因组区域。这些基线数据为进一步研究和鉴定更可靠的分子标记提供了关键基础。
