Association of β-globin polymorphisms and tolerance to haemonchosis in ewes and lambs of different sheep breeds

Author(s)

Kapritchkoff, Rafaela Tami Ikeda ; Okino, Cintia Hiromi ; Niciura, Simone Cristina Meo ; Bello, Hornblenda Joaquina Silva ; Matos, Renata Silva ; Melito, Glaucia Roberta ; Bressani, Flavia Aline ; Esteves, Sergio Novita ; Chagas, Ana Carolina de Souza

• Document type: Journal article
• Source: Veterinary Parasitology; v. 328, p. 8-pg., 2024-03-21.

Abstract

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 beta-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 Ines (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 beta-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 beta-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 HbBB. The same pattern was found in SI when analyzing each breed separately. No significant association was found between beta-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 beta-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. (AU)

• FAPESP's process: 22/00776-8 - Determination of the relationship between ovine ²-globin haplotypes and resistance to infection by Haemonchus contortus in Santa Inês, Texel and White Dorper breeds
• Grantee: Rafaela Tami Ikeda Kapritchkoff
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 21/02535-5 - Parasite-host-environment approach to control anthelmintic resistance in sheep flocks
• Grantee: Ana Carolina de Souza Chagas
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 22/07720-8 - Study of the effect of parasite replacement on the anthelmintic resistance of Haemonchus contortus in sheep breeds
• Grantee: Hornblenda Joaquina Silva Bello
• Support Opportunities: Scholarships in Brazil - Post-Doctoral