Parasitological study and evaluation of anthelmintic resistance in Maremmano horses: Preliminary data

A study was carried out on nematode infections and anthelmintic resistance in Maremmano horse in Tuscany and Lazio (Central Italy). Eighty three horses from 13 breeding farms were randomly included in the study. Faecal examinations were performed to assess the prevalence and the intensity (egg per gram: epg) of infections. Forty horses with epg 150 and not treated with anthelmintics for at least 10 weeks, were selected to assess anthelmintic resistance. Horses were divided into 4 groups of 10 animals each; 3 groups were treated with a single dose of ivermectin, pyrantel pamoate and fenbendazole, respectively, at recomanded dose. The remaining fourth group was used as untreated control. Faecal samples were collected from each horse on the treatment day (T-0), and 14 (T-14) and 21 (T-21) days after treatment, Faecal egg counts (FEC) were carried out by McMaster technique (sensitivity 15 epg). Larval cultures were carried out on FEC positive samples. Resistance was assessed on the basis percent FEC reduction (FECR) < 90% on day 14 and 21 post treatment. Overall, the prevalences were 86.74% for intestinal strongyles (upg arithmetical mean 235) and 14.45% for cestode infections. No statistical correlations were found between prevalence, EPG counts and farm management or deworming program. On day 14, FEC showed 92.47%, 96% and 99.6% of reduction after treatment with fenbendazole, pyrantel pamoate and ivermectin, respectively. The percent of reduction was confirmed on day 21. Most larvae from faecal cultures at the different times of the study belonged to subfamily of Cythostominae (80-100%).