Development of Haemonchus contortus resistance in sheep under suppressive or targeted selective treatment with monepantel

Abstract

This study examined the development of resistance to anthelmintics in Haemonchus contortus in lambs under suppressive or selective treatment regimens that included monepantel. Twenty Ile de France and 20 Santa Ines lambs were allocated to two anthelmintic treatment regimens, based on body weight and nematode faecal egg counts (FEC): targeted selective treatment (TST) or suppressive treatment, both with monepantel. Lambs of the TST group were treated individually when they presented with a packed cell volume (PCV) ≤20%. On 7 October 2016, the lambs were allocated to clean pastures, where they grazed in separated paddocks by group until late February 2017. The experimental area was contaminated with nematodes that were introduced with the experimental Ile de France and Santa Ines lambs, naturally infected with gastrointestinal nematodes. To maintain the grazing lambs in the suppressive treatment group and their pasture as free of worms as possible, these lambs were treated with anthelmintics before being allocated to their paddock and then were periodically treated with monepantel. However, the use of a suppressive treatment regimen that included monepantel over a period of 3 months resulted in the emergence of a population of resistant H. contortus. In the TST group, there was a rapid and progressive reduction in the efficacy of monepantel, which at the end of the experiment was only 76%. The Ile de France lambs were all treated one or more times during the experiment, whereas only two Santa Ines lambs in the TST required treatment. In conclusion, a population of H. contortus resistant to monepantel emerged quickly during the rainy season, even when sheep were submitted to selective treatment.

Losses caused by gastrointestinal nematode infections in Dorper lambs under two nutritional status

“…It is a blood-sucking parasite that causes, in acute infections, mortality, which is considered the most important economic effect attributable to this parasite (BARGER & COX, 1984). In addition, it presents high prolificacy and great capacity of developing anthelmintic resistance (ALBUQUERQUE et al, 2017;MARTINS et al, 2017;OLIVEIRA et al, 2017). Other trichostrongylid parasites produce significant reductions in weight gain, which is the case of Trichostrongylus colubriformis, considered the second most important nematode in sheep in Brazil (WILMSEN et al, 2014;ALMEIDA et al, 2018).…”

Resistance to monepantel in multiresistant gastrointestinal nematodes in sheep flocks in Rio Grande do Sul

“…Resistance to monepantel in sheep and goats was reported for the first time in New Zealand (SCOTT et al, 2013). Since then, resistance to this product has been detected in Uruguay (MEDEROS et al, 2014) and the Netherlands (VAN DEN BROM et al, 2015), and sheep helminths, particularly Haemonchus contortus, are resistant to monepantel in Brazilian breeds (CINTRA et al, 2016;ALBUQUERQUE et al, 2017;MARTINS et al, 2017).…”

“…Monepantel is the first molecule of an entirely new chemical group to appear on the market after more than 25 years (KAMINSKY et al, 2008). Despite the recent development of monepantel, cases of resistance to this drug were observed in sheep and goats in New Zealand (SCOTT et al, 2013), Uruguay (MEDEROS et al, 2014, and Brazil in the state of São Paulo (ALBUQUERQUE et al, 2017;MARTINS et al, 2017) and Paraná (CINTRA et al, 2016).…”

Advances in the Development of Technologies Using Essential Oils for Control of Parasites of Small Ruminants

“…Durante muito tempo o controle dos parasitos foi realizado quase que exclusivamente por meio de compostos químicos sintéticos. Diversos estudos descrevem a resistência do principal parasito de pequenos ruminantes, o nematoide Haemonchus contortus aos compostos sintéticos disponíveis no mercado (ALBUQUERQUE et al, 2017;BERTON et al, 2017;KNUBBEN-SCHWEIZER e PFISTER, 2017;ONZIMA et al, 2017), entretanto, o uso indevido desses produtos vem selecionando populações resistentes a diversas bases químicas.…”