Anthelminthic resistance of gastrointestinal nematodes in sheep to monepantel treatment in central region of Rio Grande do Sul, Brazil

Abstract

Given the numerous reports of anthelminthic resistance of sheep nematodes to different anthelmintic compounds, this study aimed to evaluate the resistance status of gastrointestinal nematodes from naturally infected sheep to monepantel in the state of Rio Grande do Sul. Four farms that present extensive raising system and absence of anthelmintic treatment for 60 days were selected for the study. Lambs that present counts of eggs per gram of feces (EPG) ≥200 (sensitivity of 50 EPG) one day (D-1) before the treatment were select for the study and randomly separated into two groups, a control group and an experimental group treated with monepantel. Feces were collected 9 days after the treatment (D+9) for EPG counts and fecal culture. The monepantel was 100% effective only on 2. The efficacy found on farm 1, 3, and 4 were 2.82%, 25.8%, and 78.4%, respectably. There were no viable larvae post-treatment at farm 2, but the genera Haemonchus, Trichostrongylus, Cooperia, and Strongyloides were resistant to it at the other farms. This study shows the presence of parasites resistant to the treatment with monepantel, pointing to the importance of monitoring its efficacy in sheep flocks of Rio Grande do Sul, Brazil.

Genotypic characterisation of monepantel resistance in historical and newly derived field strains of Teladorsagia circumcincta

“…The first cases of resistance were highlighted in field isolates of T. circumcincta and Trichostrongylus colubriformis in New Zealand flocks of sheep and goats (Leathwick et al, 2013; Scott et al, 2013). Resistance to MPTL has since also been reported in Haemonchus contortus from sheep in Uruguay (Mederos et al, 2014), the Netherlands (Van den Brom et al, 2015), Australia (Sales and Love, 2016) and Brazil (Martins et al, 2017; Ramos et al, 2018), in T. colubriformis in Brazilian sheep and goat flocks (Cintra et al, 2016, 2018) and in Trichostrongylus vitrinus , T. circumcincta and Oesophagostomum venulosum from a UK flock (Hamer et al, 2018; Bartley et al, 2019).…”

Suppressive treatment with monepantel and the fast selection for phenotypically resistant trichostrongylids of sheep

“…Other reports followed from Uruguay (Mederos et al ., 2014), the Netherlands (van den Brom et al ., 2015) and Sweden (Höglund et al ., 2020). In Brazil, cases of MNT resistance of Haemonchus contortus have been described in São Paulo (Albuquerque et al ., 2017; Martins et al ., 2017) and Rio Grande do Sul (Ramos et al ., 2018). Resistance to MNT was also reported in Paraná against T. colubriformis and Oesophagostomum columbianum (Cintra et al ., 2016) but it was not observed in H. contortus or T. axei .…”

Biocontrole de carrapato bovino rhipicephalus (boophilus) microplus “in vitro” com alho desidratado

“…Estes, em sua maioria, demandam períodos de carência distintos após seu uso, impossibilitando a comercialização dos animais pela presença de resíduos medicamentosos na carne e leite, acarretando em danos à saúde pública. Além do mais, o uso inadequado destes produtos pode causar resistência parasitária (Cezar et al, 2010; Research, Society and Development, v. 10, n. 8, e44910816681, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i8.16681 Silva et al, 2012;Ramos et al, 2018;Vieira, 2020). Para Torres (2010), o tratamento com acaricidas químicos podem causar uma alta toxicidade ao meio ambiente, gerando problemas como o desequilíbrio ecológico nas populações tanto de carrapatos como de predadores.…”