Time required by different anthelmintics to reach expected efficacy levels in horses infected by strongyles

•Cessation in egg shedding four days after treatment with ivermectin.•Cessation in egg shedding three days after treatment with moxidectin.•The presence of fenbendazole- and piperazine-resistant cyathostomins was recorded. The aim of this study was to determine the time required by different anthelm...

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Published in:	Veterinary parasitology Vol. 229; pp. 90 - 92
Main Authors:	Saes, Isabela de Lima, Vera, João H.S., Fachiolli, Daniele F., Yamada, Paulo H., Dellaqua, João V.T., Saes, Rafaela de Lima, Amarante, Alessandro F.T., Soutello, Ricardo V.G.
Format:	Journal Article
Language:	English
Published:	Netherlands Elsevier B.V 15-10-2016
Subjects:	Animals Anthelmintics - pharmacokinetics Anthelmintics - therapeutic use Egg shedding Equine Feces - parasitology Female Fenbendazole Horses Ivermectin Male Moxidectin Parasite Egg Count - veterinary Reduction in EPG Strongyle Infections, Equine - drug therapy Fenbendazole Equine Moxidectin Egg shedding Reduction in EPG Ivermectin
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Summary:	•Cessation in egg shedding four days after treatment with ivermectin.•Cessation in egg shedding three days after treatment with moxidectin.•The presence of fenbendazole- and piperazine-resistant cyathostomins was recorded. The aim of this study was to determine the time required by different anthelmintic agents to reduce strongyle egg shedding in horses. Fifty horses were divided into five homogenous groups based on faecal egg counts (FECs). Treatment groups received either ivermectin; moxidectin; fenbendazole; piperazine; or no treatment (control group). Faecal examinations were performed 4, 8, 12, 18, 24, 36 and 48h after the anthelmintic treatment. After this period, faecal samples were taken every 24h over the next 12days and finally on alternate days (48-h intervals) for another 14days until the end of the experiment (28days post-treatment). The faecal egg count reduction (FECR) was calculated based on the post-treatment mean FECs in the controls and treated animals. Eggs were absent from the faecal examinations beginning at 72h and 4days, respectively, following treatment with moxidectin or ivermectin. Piperazine showed an FECR greater than 95% from 48h up to 9days post-treatment, with the highest FECR value recorded at 7days post-treatment (98.1%). However, the FECR was lower than 90% in the last two samplings (26 and 28days post-treatment). The febendazole group presented the lowest efficacy with FECR below 90% in all samplings. The faecal cultures showed that at the beginning of the trial, all of the groups presented with mixed infections and were predominantly composed of cyathostomins (92.8%), followed by Strongylus vulgaris (5.6%) and Triodontophorus serratus (1.6%). Only cyathostomin larvae were identified following treatment with fenbendazole or piperazine. In conclusion, horses in the present study had a segment of the cyathostomin population with resistance to fenbendazole and piperazine. The strongyle population was susceptible to macrocyclic lactones, with cessation in egg shedding three and four days after treatment with moxidectin and ivermectin, respectively.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0304-4017 1873-2550
DOI:	10.1016/j.vetpar.2016.10.002