Worm replacement with susceptible Haemonchus contortus benefits weight gain, reduces anthelmintic treatments and impacts sheep breeds differently

Autor(es)

Bello, Hornblenda Joaquina Silva ; Kapritchkoff, Rafaela Tami Ikeda ; Santos, Juliana de Carvalho ; Melito, Glaucia Roberta ; Niciura, Simone Cristina Meo ; Esteves, Sergio Novita ; Bressani, Flavia Aline ; Chagas, Ana Carolina de Souza

• Tipo de documento: Artigo Científico
• Fonte: Veterinary Parasitology; v. 337, p. 11-pg., 2025-07-01.

Resumo

This study evaluated the effect of partial and total replacement of Haemonchus contortus in sheep breeds. Pregnant ewes of White Dorper (DO), Santa Ines (SI) and Texel (TX) breeds were allocated into three groups: Control (C), Partial Replacement (PR) and Total Replacement (TR). PR and TR ewes received anthelmintics (AH), were artificially infected with H. contortus-susceptible isolate and grazed on resistant-infested or worm-free paddocks, respectively. Control animals were untreated and naturally infected. 106 lambs were born and kept in the paddocks of their respective mothers. Their egg count per gram of feces (FEC) and packed cell volume (PCV) were recorded every 21 days, until 189 days old. Fecal Egg Count Reduction Test revealed AH efficacy of 85 %, 92 % and 97 % in the C, PR and TR groups, respectively, for ewes and 60 %, 74 % and 98 %, respectively, for lambs at day 147. SI animals (p < 0.001) received fewer AH treatments and presented a higher PCV than DO and TX, reaching similar weight gain to the other breeds. Male lambs (p <0.001) presented a higher FEC, lower PCV and lower frequency of Famacha score 1. Higher age at weaning resulted in a lower FEC (p = 0.0073), higher PCV (p = 0.002), and higher frequencies of Famacha 1 and body condition scores 3 and 4. AH treatment was more efficient after worm replacement, reducing FEC (p <0.001) and favoring weight gain in the PR and TR groups. Avoiding early weaning, adopting selective AH treatments and using more resistant sheep breeds may delay the reestablishment of resistance after worm replacement. (AU)

• Processo FAPESP: 22/00118-0 - Substituição parasitária como abordagem para a mitigação da resistência anti-helmíntica
• Beneficiário: Juliana de Carvalho Santos
• Modalidade de apoio: Bolsas no Brasil - Programa Capacitação - Treinamento Técnico
• Processo FAPESP: 22/00776-8 - Determinação da relação entre haplótipos da ²-globina ovina e resistência à infecção por Haemonchus contortus nas raças Santa Inês, Texel e White Dorper
• Beneficiário: Rafaela Tami Ikeda Kapritchkoff
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 22/07720-8 - Estudo do efeito da substituição parasitária sobre a resistência anti-helmíntica de Haemonchus contortus em raças ovinas
• Beneficiário: Hornblenda Joaquina Silva Bello
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 21/02535-5 - Abordagem parasita-hospedeiro-ambiente para controle da resistência anti-helmíntica em rebanhos ovinos
• Beneficiário: Ana Carolina de Souza Chagas
• Modalidade de apoio: Auxílio à Pesquisa - Temático