Siriporn Bunnada, Juasook Amornrat, Neelapaijit Nattarika, Kaewta Piyatida, Wu Zhiliang
Veterinary Infectious Disease Research Unit, Faculty of Veterinary Sciences, Mahasarakham University, Maha Sarakham, Thailand.
Bioveterinary Research Unit, Faculty of Veterinary Sciences, Mahasarakham University, Maha Sarakham, Thailand.
Vet World. 2023 Aug;16(8):1661-1666. doi: 10.14202/vetworld.2023.1661-1666. Epub 2023 Aug 19.
Administration is the main strategy for controlling ectoparasites in dogs. Ivermectin and fipronil are most extensively used to prevent and treat sensu lato infestation in dogs in Thailand. Several researchers have reported resistance to acaricides in s.l. globally, but documentation of acaricide resistance in the tick population in Thailand is lacking. In this study, we investigated the status of resistance to commonly used acaricides in Thailand in s.l.
Engorged brown dog tick females (10 tick populations) were field-collected directly from parasitized dogs in Maha Sarakham, Thailand, for toxicological bioassays with ivermectin and fipronil. Bioassays were performed in three replicates at 25°C-27°C and 80%-85% relative humidity under a 12-h/12-h photoperiod. The 50% of lethal concentration and its confidence intervals and the slope were estimated for each tick population using probit analysis. Resistance ratios (RRs) of field ticks were characterized based on the relative susceptible population of each acaricide.
Six tick populations (P1-6) were tested for resistance to ivermectin, three of which (P2-4) exhibited low-level resistance to ivermectin (RR = 2.115-2.176). Of four tick populations (P7-10) treated with fipronil, two exhibited moderate-to-severe resistance (P7 and P9, RR = 21.684 and 4.387, respectively). All tick populations deemed resistant to acaricides had a history of exposure.
Based on RR values, four s.l. tick populations from Maha Sarakham province were resistant to ivermectin and fipronil. To the best of our knowledge, this represents the first documentation of acaricide-resistant populations of s.l. in Thailand, and recommendations on tick control programs must be formulated with veterinarians and pet owners to prevent the development of further resistance.
药浴是控制犬体外寄生虫的主要策略。伊维菌素和氟虫腈在泰国犬类中被最广泛地用于预防和治疗广义上的蜱虫感染。全球有几位研究人员报告了广义上对杀螨剂的抗性，但泰国蜱虫种群中杀螨剂抗性的文献资料却很缺乏。在本研究中，我们调查了泰国广义上对常用杀螨剂的抗性状况。
从泰国玛哈沙拉堪的寄生犬身上直接采集饱血的棕色犬蜱雌性（10个蜱虫种群），用于伊维菌素和氟虫腈的毒理学生物测定。生物测定在25°C - 27°C、相对湿度80% - 85%、12小时光照/12小时黑暗的光周期下进行三次重复。使用概率分析估计每个蜱虫种群的半数致死浓度及其置信区间和斜率。根据每种杀螨剂的相对敏感种群来表征野外蜱虫的抗性比率（RRs）。
对六个蜱虫种群（P1 - 6）进行了伊维菌素抗性测试，其中三个种群（P2 - 4）对伊维菌素有低水平抗性（RR = 2.115 - 2.176）。在用氟虫腈处理的四个蜱虫种群（P7 - 10）中，有两个表现出中度至重度抗性（P7和P9，RR分别为21.684和4.387）。所有被认为对杀螨剂有抗性的蜱虫种群都有接触史。
根据RR值，来自玛哈沙拉堪省的四个广义上的蜱虫种群对伊维菌素和氟虫腈有抗性。据我们所知，这是泰国广义上杀螨剂抗性蜱虫种群的首次记录，必须与兽医和宠物主人一起制定蜱虫控制计划的建议，以防止进一步抗性的发展。
