Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista (UNESP), Via de Acesso Prof. Paulo Donato Castellane, s/n, Jaboticabal, São Paulo 14884-900, Brazil.
Embrapa Pecuária Sudeste, Rodovia Washington Luiz, Km 234 s/n, Fazenda Canchim, P.O. Box 339, São Carlos, São Paulo 13560-970, Brazil.
Vet Parasitol. 2024 Jun;328:110163. doi: 10.1016/j.vetpar.2024.110163. Epub 2024 Mar 7.
Gastrointestinal nematodes (GIN), especially Haemonchus contortus, represent a significant challenge for sheep production. Given the global concern about GIN anthelmintic resistance, alternative control methods able to reduce the dependence on these drugs are highly advisable. Since previous studies have shown that sheep carrying the Hb-A allele of β-globin are more resistant to H. contortus, this study aimed to investigate the relationship between the different haplotypes (Hb-AA, Hb-AB and Hb-BB) and phenotypes in Santa Inês (SI), Texel (TX) and White Dorper (DO) breeds infected with H. contortus. Blood samples were collected from 180 ewes and 123 lambs of the three breeds for DNA extraction followed by qPCR using a hydrolysis probe to identify the β-globin haplotypes. Phenotypic data, including fecal egg count (FEC), packed cell volume (PCV), FAMACHA score and body condition score for ewes and lambs, as well as weight gain for lambs, were collected. The genotypic frequencies of β-globin for ewes and lambs were, respectively: 21.7% and 21.4% Hb-AA, 50% and 50% Hb-AB and 28.3% and 28.6% Hb-BB in SI; 0% and 0% Hb-AA, 18.6% and 9.4% Hb-AB and 81.4% and 90.6% Hb-BB in TX; and 0% and 0% Hb-AA, 13.1% and 0% Hb-AB and 86.9% and 100% Hb-BB in DO. In ewes, mean PCV differed (p<0.05) between the three haplotypes, with higher PCV in Hb-AA animals, followed by Hb-AB and Hb-BB. When considering each breed separately, SI Hb-AA ewes presented higher PCV (p<0.05), highlighting that even in a breed already considered resistant, animals with Hb-AA haplotype showed superior performance. Lambs with the Hb-AA haplotype exhibited a higher (p<0.05) mean PCV compared to those with Hb-AB and Hb-BB. The same pattern was found in SI when analyzing each breed separately. No significant association was found between β-globin haplotypes and FEC, FAMACHA score, body condition score, or weight gain. Nevertheless, given that anemia is the major clinical sign of haemonchosis, our findings on PCV reinforce that sheep carrying the Hb-A allele of β-globin are more tolerant to haemonchosis. This study may support the development of a valuable tool, targeting genetic selection for GIN control, reducing the dependence on anthelmintics and boosting sheep production worldwide.
胃肠道线虫（GIN），特别是捻转血矛线虫，对绵羊生产构成了重大挑战。鉴于全球对 GIN 驱虫药耐药性的关注，能够减少对这些药物依赖的替代控制方法是非常可取的。由于先前的研究表明，携带β-珠蛋白 Hb-A 等位基因的绵羊对捻转血矛线虫更具抗性，因此本研究旨在调查不同哈普特（Hb-AA、Hb-AB 和 Hb-BB）与感染捻转血矛线虫的 Santa Inês（SI）、Texel（TX）和 White Dorper（DO）品种之间的关系。从三个品种的 180 只母羊和 123 只羔羊中采集血液样本进行 DNA 提取，然后使用水解探针进行 qPCR 以鉴定β-珠蛋白哈普特。收集了与母羊和羔羊有关的表型数据，包括粪便卵计数（FEC）、红细胞压积（PCV）、FAMACHA 评分和身体状况评分，以及羔羊体重增加。母羊和羔羊的β-珠蛋白基因型频率分别为：SI 中的 21.7%和 21.4% Hb-AA、50%和 50% Hb-AB 和 28.3%和 28.6% Hb-BB；TX 中的 0%和 0% Hb-AA、18.6%和 9.4% Hb-AB 和 81.4%和 90.6% Hb-BB；DO 中的 0%和 0% Hb-AA、13.1%和 0% Hb-AB 和 86.9%和 100% Hb-BB。在母羊中，三个哈普特之间的平均 PCV 存在差异（p<0.05），Hb-AA 动物的 PCV 较高，其次是 Hb-AB 和 Hb-BB。当分别考虑每个品种时，SI Hb-AA 母羊的 PCV 更高（p<0.05），这突出表明，即使在已经被认为具有抗性的品种中，携带 Hb-AA 哈普特的动物表现也更优。携带 Hb-AA 哈普特的羔羊的平均 PCV 更高（p<0.05），与携带 Hb-AB 和 Hb-BB 的羔羊相比。当分别分析每个品种时，在 SI 中也发现了相同的模式。β-珠蛋白哈普特与 FEC、FAMACHA 评分、身体状况评分或体重增加之间没有发现显著的相关性。然而，鉴于贫血是血矛线虫病的主要临床症状，我们关于 PCV 的发现证实了携带β-珠蛋白 Hb-A 等位基因的绵羊对血矛线虫病的耐受性更强。本研究可能为控制 GIN 的遗传选择提供有价值的工具，减少对驱虫药的依赖，并促进全球绵羊生产。
