Ali Qasim, Rashid Imran, Shabbir Muhammad Zubair, Shahzad Kashif, Ashraf Kamran, Sargison Neil D, Chaudhry Umer
Department of Parasitology, University of Veterinary and Animal Sciences Lahore, Pakistan.
Quality Operations Labsoratory, University of Veterinary and Animal Sciences, Lahore, Pakistan.
Vet Parasitol. 2019 Jan;265:48-54. doi: 10.1016/j.vetpar.2018.12.001. Epub 2018 Dec 11.
Benzimidazoles have been intensively (for over 40 years) used in the livestock sector, particularly in small ruminants. This has been led to the widespread emergence of resistance in a number of small ruminant parasite species, especially Haemonchus contortus. In many countries benzimidazole resistance has severely compromised the control of H. contortus in small ruminants; but there is a little information on benzimidazole resistance in H. contortus infecting buffalo and cattle. Resistance to benzimidazoles have also been reported in the large ruminant parasite, Haemonchus placei, but again there is relatively little information on its prevalence. Hence it is very important to understand how resistance-conferring mutations emerge and spread in both parasites in buffalo and cattle hosts in order to develop approaches for the recognition of the problem at an early stage of its development. The present study suggests that the F200Y (TAC) mutation is common in H. contortus, being detected in 5/7 populations at frequencies between 7 and 57%. Furthermore, 6/10 H. placei populations contained the F200Y (TAC) mutation, albeit at low frequencies of between 0.4 and 5%. The phylogenetic analysis suggests that the F200Y (TAC) mutation in H. contortus has emerged on multiple occasions in the region, with at least three independent emergences across the populations. In contrast, the F200Y (TAC) resistance-conferring mutation in H. placei is only seen on a single haplotype. A high level frequency of the resistance haplotypes in the region, suggests that the unique resistance conferring-mutation has spread from a single emergence; likely by anthropogenic animal movement. Overall, these results provide the first clear genetic evidence for the spread of benzimidazole resistance-conferring mutations to multiple different locations from a single emergence in H. placei; while being consistent with previous small ruminant-based observations of multiple emergence of resistance mutations in H. contortus.
苯并咪唑已在畜牧业中广泛使用（超过40年），尤其是在小型反刍动物中。这导致了许多小型反刍动物寄生虫物种中耐药性的广泛出现，特别是捻转血矛线虫。在许多国家，苯并咪唑耐药性严重影响了小型反刍动物中捻转血矛线虫的控制；但关于感染水牛和牛的捻转血矛线虫对苯并咪唑的耐药性信息很少。大型反刍动物寄生虫——长刺血矛线虫对苯并咪唑的耐药性也有报道，但同样关于其流行情况的信息相对较少。因此，了解赋予耐药性的突变如何在水牛和牛宿主中的这两种寄生虫中出现和传播，对于制定在问题发展早期阶段识别该问题的方法非常重要。本研究表明，F200Y（TAC）突变在捻转血矛线虫中很常见，在7个种群中的5个中被检测到，频率在7%至57%之间。此外，10个长刺血矛线虫种群中有6个含有F200Y（TAC）突变，尽管频率较低，在0.4%至5%之间。系统发育分析表明，捻转血矛线虫中的F200Y（TAC）突变在该地区多次出现，至少在不同种群中有三次独立出现。相比之下，长刺血矛线虫中赋予耐药性的F200Y（TAC）突变仅出现在一个单倍型上。该地区耐药单倍型的高频率表明，独特的耐药性赋予突变是从单次出现传播而来的；可能是通过人为的动物移动。总体而言，这些结果首次提供了明确的遗传证据，证明赋予苯并咪唑耐药性的突变从长刺血矛线虫的单次出现传播到多个不同地点；同时与之前基于小型反刍动物的观察结果一致，即捻转血矛线虫中耐药性突变多次出现。
