RESUMO

Parascaris spp. are the most dangerous parasites of foals, and their presence is related to poor growth, weight loss, colics and death after impaction or intestinal perforation.The reduction in the effectiveness of antiparasitics has become a serious threat to animal health and there is little prospect of the emergence of a new anthelmintic for horses. Therefore, the objective was to evaluate the effectiveness of active principles used in the control of ascarids in Creole foals, in a ownership located in the south of Rio Grande do Sul, Brazil. The Gordon and Whitlock technique was used on 12 samples of foal faeces that were collected on the date of administration of the antiparasitic and 14 days afterwards. The evaluation of the effectiveness of the active principles was carried out through the Faecal Egg Count Reduction Test (FECRT). All the anthelmintics used failed against Parascaris spp. and therefore should not be used to control infections caused by these helminths in the population studied. In addition, generalized resistance of ascarids to avermectins was observed. The results also show that other management practices should be implemented on the ownership, in an attempt to reduce infections by these helminths.

Parascaris spp. são os parasitas mais perigosos dos potros e estão relacionados ao baixo crescimento, perda de peso, cólicas e morte após impactação ou perfuração intestinal. A redução da eficácia dos antiparasitários tornou-se uma séria ameaça à saúde animal e há poucas perspectivas de surgimento de um novo anti-helmíntico para equinos. Portanto, objetivou-se avaliar a eficácia dos princípios ativos utilizados no controle de ascarídeos em potros crioulos, em uma propriedade localizada no sul do Rio Grande do Sul, Brasil. Foram utilizados os resultados da técnica de Gordon e Whitlock de 12 amostras de fezes de potros, que foram coletadas na data da administração do antiparasitário e 14 dias após. A avaliação da eficácia dos princípios ativos foi realizada por meio do Teste de Redução de Contagem de Ovos nas Fezes (TRCOF). Todos os anti-helmínticos utilizados falharam contra Parascaris spp. e não devem ser usados para controlar as infecções desses helmintos na população estudada, além disso, há uma resistência generalizada dos ascarídeos contra as avermectinas. Os resultados também mostram que outras práticas de manejo devem ser implementadas na propriedade, na tentativa de reduzir as infecções por esses helmintos.

Assuntos

RESUMO

Macrocyclic lactones are the most widely used drugs for the control of gastrointestinal nematodes of horses in Argentina. Ivermectin and moxidectin are used as broad spectrum anthelmintics and although there are several international reports on the resistance of Parascaris spp., the resistance status of the local nematode population is largely unknow. This report informs a case of suboptimal efficacy to both drugs to control Parascaris spp in foals in central Argentina. In February 2018, routine fecal parasite egg counts showed a moderate-high number of Parascaris spp eggs (mean = 680 eggs per gram of feces) in foals treated approximately one month before with moxidectin. Upon suspicion of resistance of this parasite to the macrocyclic lactones, 24 of these animals were selected for a fecal egg count reduction test (FECRT). Twelve foals were treated with ivermectin and the remaining 12 animals with moxidectin. Two weeks after treatment, the FECRT was 48.1% and 34.8% for moxidectin and ivermectin respectively (25% of the animals increased the number of eggs in feces after treatment). Five days later, the administration of fenbendazole resulted in a FECRT = 100%. The monitoring of the status of susceptibility or resistance in each establishment is critical for the design of control programs based on rational and sustainable use of anthelmintics.

Assuntos