Esteban-Ballesteros Myriam, Rojo-Vázquez Francisco A, Skuce Philip J, Melville Lynsey, González-Lanza Camino, Martínez-Valladares María
Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n, 24071, León, Spain.
Instituto de Ganadería de Montaña (CSIC-Universidad de León), Finca Marzanas, Grulleros, 24346, León, Spain.
BMC Vet Res. 2017 Mar 20;13(1):71. doi: 10.1186/s12917-017-0992-9.
Benzimidazole (BZ) resistance in gastrointestinal nematodes is associated with a single nucleotide polymorphism (SNP) at codons 167, 198 and 200 in the isotype 1 of beta-tubulin gene although in some species these SNPs have also been associated with resistance to macrocyclic lactones. In the present study we compared the levels of resistance in Teladorsagia circumcincta and Trichostrongylus colubriformis by means of the faecal egg reduction test (FECRT) and the percentage of resistant alleles obtained after pyrosequencing. The study was conducted in 10 naturally infected sheep flocks. Each flock was divided into three groups: i) group treated with albendazole (ABZ); ii) group treated with ivermectin (IVM); iii) untreated group. The number of eggs excreted per gram of faeces was estimated at day 0 and 14 post-treatment.
Resistance to ABZ was observed in 12.5% (1/8) of the flocks and to IVM in 44.4% (4/9) of them. One flock was resistant to both drugs according to FECRT. Coprocultures were performed at the same dates to collect L3 for DNA extraction from pooled larvae and to determine the resistant allele frequencies by pyrosequencing analysis. In T. circumcincta, SNPs were not found at any of the three codons before treatment; after the administration of ABZ, SNPs were present only in two different flocks, one of them with a frequency of 23.8% at SNP 167, and the other 13.2% % at SNP 198. In relation to T. colubriformis, we found the SNP200 before treatment in 33.3% (3/9) of the flocks with values between 48.5 and 87.8%. After treatment with ABZ and IVM, the prevalence of this SNP increased to 75 and 100% of the flocks, with a mean frequency of 95.1% and 82.6%, respectively.
The frequencies observed for SNP200 in T. colubriformis indicate that the presence of resistance is more common than revealed by the FECRT.
胃肠道线虫对苯并咪唑（BZ）的抗性与β-微管蛋白基因同种型1中第167、198和200位密码子处的单核苷酸多态性（SNP）相关，尽管在某些物种中，这些SNP也与对大环内酯类药物的抗性有关。在本研究中，我们通过粪便虫卵减少试验（FECRT）和焦磷酸测序后获得的抗性等位基因百分比，比较了环形泰勒虫和蛇形毛圆线虫的抗性水平。该研究在10个自然感染的绵羊群体中进行。每个群体分为三组：i）用阿苯达唑（ABZ）治疗的组；ii）用伊维菌素（IVM）治疗的组；iii）未治疗组。在治疗后第0天和第14天估计每克粪便中排出的虫卵数量。
在12.5%（1/8）的群体中观察到对ABZ的抗性，在44.4%（4/9）的群体中观察到对IVM的抗性。根据FECRT，有一个群体对两种药物均有抗性。在相同日期进行粪便培养，以收集L3用于从混合幼虫中提取DNA，并通过焦磷酸测序分析确定抗性等位基因频率。在环形泰勒虫中，治疗前在三个密码子中的任何一个都未发现SNP；施用ABZ后，仅在两个不同的群体中出现SNP，其中一个群体在SNP 167处的频率为23.8%，另一个群体在SNP 198处的频率为13.2%。关于蛇形毛圆线虫，在治疗前我们在33.3%（3/9）的群体中发现SNP200，其值在48.5%至87.8%之间。用ABZ和IVM治疗后，该SNP的流行率分别增加到群体的75%和100%，平均频率分别为95.1%和82.6%。
在蛇形毛圆线虫中观察到的SNP200频率表明，抗性的存在比FECRT所显示的更为常见。
