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Becher, Anne Monika (2010): Untersuchungen zur Einführung der Selektiven Anthelminthischen Therapie beim Pferd im Raum Salzburg. Dissertation, LMU München: Tierärztliche Fakultät



From March until November 2008 faecal samples of 281 horses and 5 donkeys in an area of 40 km around Salzburg were analysed with a modified McMaster method for Strongyle eggs. Each time a faecal egg count (FEC) exceeded 250 eggs per gram faeces (EPG) the horse was treated with either pyrantel, ivermectin or moxidectin and FEC reduction test was done on day 14 and 21. Additionally 259 horse owners participated in an online questionnaire survey about worm control. In 52 (40.3 %) horses no strongyle eggs were detected in any of nine samples. In 39 horses (30.2 %), eggs were detected in at least one sample, but the egg count did not exceed 250 EPG at any of the nine sampling occasions. The remainder of the horses (29.5 %) had to be treated at least once due to the FEC exceeding 250 EPG. The number of treatments was reduced to 46 % of the number of treatments in the year before. The maximal and mean FEC both dropped significantly after the start of the study. There was a slight statistically significant negative correlation between the age of the horses and the maximal and mean FEC of each horse. The first FEC had a positive statistically significant correlation with the maximal FECs in the following eight months. Furthermore horses with more treatments had a higher first FEC than horses with less or no treatments. The efficacy of ivermectin and moxidectin was 100 %. On one farm resistance to pyrantel was detected. 80,2 % of the participants of the questionnaire survey knew selective anthelmintic treatment and 85,7 % chose the correct definition of resistance. The avoidance of the development of anthelmintic resistance was very important for 82,6 % of the participants. These results suggest that selective anthelmintic treatment can reduce the pasture contamination with strongyle eggs as well as the number of anthelmintic treatments. While using pyrantel the efficacy of this drug should be monitored. Furthermore these data can be helpful to design selective anthelmintic treatment programs, which can be applied by equine practitioners. The participating horse owners prefer this method of worm control, as it is the only one that avoids the development of resistance.