Reduction of egg reappearance period of cyathostomins in naturally infected horses after increasing doses of ivermectin in Brazil: a grim picture for sustainable parasite control.
Abstract: Cyathostomins are the largest group of parasites in horses that can be controlled by ivermectin (IVM). This study aimed to run a four-dose titration trial of IVM in 28 naturally infected Thoroughbred yearlings. The local Strongyle population had been recorded to be resistant to IVM (200 µg/kg). The parasite fecal egg count (FEC) was performed to investigate the egg reappearance period (ERP) of two and five weeks (w2pt and w5pt) after IVM treatment. FEC was > 1000 on day zero for all groups. Although 100% FEC reduction was reported at w2pt for all concentrations, the FEC at w5pt revealed < 83% efficacy. This study reports the reduction of ERP using the label dose as well as 300, and 400 µg/kg (double dose) of IVM. The protocol allowed IVM to significantly suppress FEC w2pt although not eliminating adult worms, failing to guarantee an extension of its protection period over 8 weeks. Moreover, the FEC at w5pt possibly means the infection was not cleared, and worms reestablished egg laying. We raised the possibility of withdrawing IVM of control programs when the drug has less than 80% FEC reduction at w5pt. Ciatostomíneos são o maior grupo de parasitos de equinos, controlados com ivermectina (IVM). Este estudo teve o objetivo de realizar um teste com quatro doses de IVM, em 28 potros Puro-Sangue Inglês. Os estrôngilos eram resistentes a IVM (200 µg/kg). A contagem de ovos por grama de fezes (OPG) foi realizada após tratamento (pt), para determinar o período de reaparecimento de ovos (PRO) após duas e cinco semanas (s2pt e s5pt). A OPG foi >1000 para todos os grupos. Observou-se 100% de redução na OPG na s2pt para todas as concentrações de IVM. A OPG na s5pt revelou < 83% de redução. Este estudo relata uma redução considerável do PRO utilizando a dose de bula, e as doses de 300 e 400 μg/kg (dobro da dose) de IVM contra ciatostomíneos em equinos. O protocolo permitiu observar a redução da postura de ovos na s2pt com IVM, falhando na garantia da extensão de proteção da droga. O reaparecimento da OPG significa que a infecção não foi eliminada. Foi levantada a possibilidade de restringir o uso de IVM, quando o medicamento atingir menos de 80% de redução da OPG na s5pt.
Publication Date: 2024-08-12 PubMed ID: 39140496PubMed Central: PMC11340864DOI: 10.1590/S1984-29612024043Google Scholar: Lookup
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Cite This Article
APA
Molento MB, Dall'Anese J, Pontarolo DV, Brandão YO, Yoshitani UY.
(2024).
Reduction of egg reappearance period of cyathostomins in naturally infected horses after increasing doses of ivermectin in Brazil: a grim picture for sustainable parasite control.
Rev Bras Parasitol Vet, 33(3), e003324.
https://doi.org/10.1590/S1984-29612024043 Publication
Researcher Affiliations
- Laboratório de Parasitologia Clínica Veterinária, Departamento de Medicina Veterinária, Universidade Federal do Paraná - UFPR, Curitiba, PR, Brasil.
- Laboratório de Parasitologia Clínica Veterinária, Departamento de Medicina Veterinária, Universidade Federal do Paraná - UFPR, Curitiba, PR, Brasil.
- Laboratório de Parasitologia Clínica Veterinária, Departamento de Medicina Veterinária, Universidade Federal do Paraná - UFPR, Curitiba, PR, Brasil.
- Laboratório de Parasitologia Clínica Veterinária, Departamento de Medicina Veterinária, Universidade Federal do Paraná - UFPR, Curitiba, PR, Brasil.
- Laboratório de Parasitologia Clínica Veterinária, Departamento de Medicina Veterinária, Universidade Federal do Paraná - UFPR, Curitiba, PR, Brasil.
MeSH Terms
- Animals
- Ivermectin / therapeutic use
- Ivermectin / administration & dosage
- Horses / parasitology
- Brazil
- Parasite Egg Count
- Horse Diseases / parasitology
- Horse Diseases / drug therapy
- Horse Diseases / diagnosis
- Female
- Antiparasitic Agents / therapeutic use
- Antiparasitic Agents / administration & dosage
- Strongyle Infections, Equine / drug therapy
- Strongyle Infections, Equine / parasitology
- Strongyle Infections, Equine / diagnosis
- Feces / parasitology
Conflict of Interest Statement
The authors have no conflicts of interest to declare.
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Citations
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