A Field Study on the Effect of Some Anthelmintics on Cyathostomins of Horses in Sweden

Abstract

The objective of the study was to investigate different aspects on the efficacy of three anthelmintics on cyathostomin nematodes of Swedish horses. A faecal egg count reduction (FECR) test was performed on 26 farms. Horses were treated orally with recommended doses of ivermectin, pyrantel pamoate or fenbendazole. Faecal samples were collected on the day of deworming and 7, 14 and 21 days later. No resistance was shown against ivermectin; the FECR was constantly >99%. The effect of pyrantel was assessed as equivocal in 6 farms 14 days after treatment; the mean FECR was 99%. As many as 72% of the fenbendazole-treated groups met the criteria for resistance; the mean FECR was 86%, ranging from 56% to 100%. A re-investigation of two farms where pyrantel resistance had been suspected clearly revealed unsatisfactory efficacy of pyrantel on one of these farms; the FECR varied from 72% to 89%. Twenty-six of the horses previously dosed with pyrantel or fenbendazole, and which still excreted >/=150 eggs per gram of faeces 14 days after treatment, were dewormed with ivermectin and fenbendazole or pyrantel in order to eliminate the remaining cyathostomins. A total of 13 cyathostomin species were identified from horses that initially received fenbendazole and seven species were identified from pyrantel-treated individuals. The egg reappearance period (ERP) following treatment with ivermectin and pyrantel was investigated on two farms. The shortest ERP after ivermectin treatment was 8 weeks and after pyrantel was 5 weeks. We conclude that no substantial reversion to benzimidazole susceptibility had taken place, although these drugs have scarcely been used (<5%) in horses for the last 10 years. Pyrantel-resistant populations of cyathostomins are present on Swedish horse farms, but the overall efficacy of pyrantel is still acceptable.

A questionnaire survey on helminth control on horse farms in Brandenburg, Germany and the assessment of risks caused by different kinds of management

“…This is less than in Britain, but more than in the other parts of Germany and also more than in Sweden (Fritzen 2005;Lind et al 2007a;Lloyd et al 2000). We do not doubt the beneficial effect of pasture hygiene on infectious pressure, rather we take our results to indicate that present pasture hygiene seems to be insufficiently performed-as was also proposed by Larsen et al (2002).…”

Field studies indicating reduced activity of ivermectin on small strongyles in horses on a farm in Central Kentucky

“…Eggs per gram of feces counts began returning at about twice as fast as when ivermectin initially was used. Strongyle EPG counts of horses treated with ivermectin typically have been negative until at least 8 weeks posttreatment (Boersema et al 1996;Lind et al 2007). In a study by Lyons et al (1992) over a 30-month study (1987 to 1990) in horses on the same farm as the present research, 1 group of horses was treated every 8 weeks (14 times) with ivermectin (Lyons et al 1992).…”

Pequeños estróngilos de los equinos. Eficacia clínica y periodo de reaparición de huevos luego del tratamiento con moxidectina y pirantel

“…De acuerdo al conocimiento de los autores del presente trabajo, no existe en nuestro país información publicada sobre la actividad de esta droga en el control de pequeños estróngilos equinos ni sobre el PRH de la misma. Los porcentajes de eficacia aquí informados y el PRH se encuentran en línea con trabajos previos publicados en otros países como por ejemplo Suecia, Francia, Inglaterra, Estados Unidos o Italia (Lind et al, 2007;Traversa et al, 2012;Lester et al, 2013;Nielsen et al, 2013;Gokubuluta et al, 2014). La administración oral de la combinación de moxidectina + oxfendazole resultó en eficacias que oscilaron entre el 99.5 y el 100% a los 14/15 días post tratamientos (Tabla 1).…”