Untersuchungen zur Einführung der Selektiven Anthelminthischen Therapie beim Pferd im Raum Salzburg

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.