Faculty of Veterinary Science, University of Nyala, P.O. Box 155, Nyala, Sudan.
Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag-Street 7-13, 14163, Berlin, Germany.
Parasit Vectors. 2021 Feb 8;14(1):101. doi: 10.1186/s13071-021-04593-w.
Benzimidazole (BZ) anthelmintics are widely used to control infections with parasitic nematodes, but BZ resistance is an emerging threat among several nematode species infecting humans and animals. In Sudan, BZ-resistant Haemonchus contortus populations were recently reported in goats in South Darfur State. The objective of this study was to collect data regarding the situation of BZ resistance in cattle parasitic nematodes in South Darfur using phenotypic and molecular approaches, besides providing some epidemiological data on nematodes in cattle.
The faecal egg count reduction test and the egg hatch test (EHT) were used to evaluate benzimidazole efficacy in cattle nematodes in five South Darfur study areas: Beleil, Kass, Nyala, Rehed Al-Birdi and Tulus. Genomic DNA was extracted from pools of third-stage larvae (L3) (n = 40) during trials, before and after treatment, and pools of adult male Haemonchus spp. (n = 18) from abattoirs. The polymorphisms F167Y, E198A and F200Y in isotype 1 β-tubulin genes of H. contortus and H. placei were analysed using Sanger and pyrosequencing.
Prevalence of gastro-intestinal helminths in cattle was 71% (313/443). Reduced albendazole faecal egg count reduction efficacy was detected in three study areas: Nyala (93.7%), Rehed Al-Birdi (89.7%) and Tulus (88.2%). In the EHT, EC values of these study areas ranged between 0.032 and 0.037 µg/ml thiabendazole. Genus-specific PCRs detected the genera Haemonchus, Trichostrongylus and Cooperia in L3 samples collected after albendazole treatment. Sanger sequencing followed by pyrosequencing assays did not detect elevated frequencies of known BZ resistance-associated alleles in codon F167Y, E198A and F200Y in isotype 1 β-tubulin gene of H. placei (≤ 11.38%). However, polymorphisms were detected in H. contortus and in samples with mixed infections with H. contortus and H. placei at codon 198, including E198L (16/58), E198V (2/58) and potentially E198Stop (1/58). All pooled L3 samples post-albendazole treatment (n = 13) were identified as H. contortus with an E198L substitution at codon 198.
To the knowledge of the authors, this is the first report of reduced albendazole efficacy in cattle in Sudan and is the first study describing an E198L substitution in phenotypically BZ-resistant nematodes collected from cattle.
苯并咪唑（BZ）驱虫药被广泛用于控制寄生线虫感染，但 BZ 耐药性是感染人和动物的几种线虫物种的新兴威胁。在苏丹，南达尔富尔州的山羊最近报告了 BZ 耐药性的旋毛虫种群。本研究的目的是使用表型和分子方法收集南达尔富尔州牛寄生虫线虫 BZ 耐药性的数据，同时提供有关牛线虫的一些流行病学数据。
在南达尔富尔的五个研究地区（贝莱尔、卡塞、尼亚拉、雷赫德阿尔比迪和图卢斯）进行了粪便卵计数减少试验（FECRT）和卵孵化试验（EHT），以评估牛线虫中苯并咪唑的疗效。在试验前和治疗后，从第三期幼虫（L3）（n=40）中提取基因组 DNA，从屠宰场的雄性 Haemonchus spp.（n=18）中提取 DNA。使用 Sanger 和焦磷酸测序分析旋毛虫和 placel 旋毛虫同工型 1β-微管蛋白基因中的 F167Y、E198A 和 F200Y 多态性。
牛胃肠道寄生虫的流行率为 71%（313/443）。在三个研究地区（尼亚拉、雷赫德阿尔比迪和图卢斯）检测到阿苯达唑粪便卵计数减少效果降低。这些研究地区的 EHT 的 EC 值在 0.032 至 0.037μg/ml 噻苯达唑之间。在阿苯达唑治疗后收集的 L3 样本中，种特异性 PCR 检测到 Haemonchus、 Trichostrongylus 和 Cooperia 属。未在同工型 1β-微管蛋白基因的 F167Y、E198A 和 F200Y 密码子中检测到已知 BZ 耐药相关等位基因的升高频率，包括 Haemonchus placei（≤11.38%）。然而，在 H. contortus 和 H. contortus 与 H. placei 混合感染的样本中检测到了 198 位密码子的多态性，包括 E198L（16/58）、E198V（2/58）和潜在的 E198Stop（1/58）。所有阿苯达唑治疗后（n=13）的 L3 混合样本均被鉴定为 H. contortus，在 198 位密码子处存在 E198L 取代。
据作者所知，这是苏丹首次报告牛阿苯达唑疗效降低，也是首次描述从牛中分离的表型 BZ 耐药线虫中存在 E198L 取代。
