Strongyle infections and parasitic control strategies in German horses ― a risk assessment

Abstract

BackgroundAs a consequence of the increasing levels of anthelmintic resistance in cyathostomes, new strategies for equine parasite control are being implemented. To assess the potential risks of these, the occurrence of strongyles was evaluated in a group of 1887 horses. The distribution of fecal egg counts (FECs), the frequency of anthelmintic drug use, and the deworming intervals were also analyzed. Between June 2012 and May 2013, 1887 fecal samples from either selectively or strategically dewormed horses were collected at 195 horse farms all over Germany and analyzed quantitatively with a modified McMaster technique. All samples with FEC ≥20 eggs per gram (EPG) were subjected to coproculture to generate third-stage larvae (LIII) for species differentiation.ResultsEgg counts were below the limit of detection (20 EPG) in 1046 (55.4%) samples and above it in 841 (44.6%) samples. Strongylus vulgaris larvae were identified in two of the 841 positive samples. Infections with cyathostomes were found on every farm. The most frequently applied anthelmintic was ivermectin (788/50.8%), followed by pyrantel (336/21.6%). The mean time since last treatment was 6.3 months. High-egg-shedding (>500 EPG) strategically dewormed horses (183/1357) were treated, on average, three times/year. The planned treatment date was already exceeded by 72.5% of the high egg-shedders and by 58.1% of the moderate (200–500 EPG) and low egg-shedders (20–199 EPG).ConclusionsS. vulgaris seems to be rare in Germany and no difference in its frequency has yet been found between selectively treated horses and horses receiving treatment in strategic intervals. However, inconsistent parasite control has been observed. Therefore, to minimize the risks for disease, consistent and efficient parasite control should be implemented.

Questionnaire study on parasite control practices on Thoroughbred and Standardbred breeding farms in New Zealand

“…Overall, regardless of age, the frequency of treatment reported in the current study was higher than reported for Thoroughbreds in Kentucky (Robert et al, 2014), in German riding horses (Schneider et al, 2014) and Danish horses (Nielsen et al, 2014b). In the Danish study, most foals and horses 1 to 3-years-old were treated twice a year, while less than 5% of horses in these age-groups were treated four or more times, and older horses were treated less often (Nielsen et al, 2014b).…”

Detection of Strongylus vulgaris in equine faecal samples by real-time PCR and larval culture – method comparison and occurrence assessment

“…Assuming a German horse population of 1.1 million [38] with a prevalence for an infection with S. vulgaris of 1% [3, 10, 19–21], a minimum of 459 horses had to be investigated since in this case the probability to detect at least one infected horse was above 99% [39]. Thus, samples of 501 of 1455 horses (horse level, 34.4%) were investigated by real-time PCR for an infection with S. vulgaris (Fig.…”

“…The intensive anthelmintic treatment regime of the last decades might be responsible for the current low occurrence of S. vulgaris (0.2–1.3%) recently determined by larval culture in German horses [10, 19–21]. However, a reliable diagnostic method for the differentiation of S. vulgaris from Cyathostominae is essential because of the significant pathology caused by the migration of S. vulgaris -larvae in the mesenteric arteries.…”

Management factors and their impact on helminthic fecal egg count in horses

“…In einer Studie von Dopfer schieden männliche Pferde deutlich weniger Eier aus als weibliche Tiere (Dopfer et al 2004) während in anderen Untersuchungen kein geschlechtsspezifischer Effekt beobachtet wurde (Fritzen et al 2010, Samson-Himmelsternja et al 2009 In der vorliegenden Studie erfolgte keine Unterscheidung zwischen kleinen und großen Strongyliden, da dafür eine Larvendifferenzierung notwendig wäre. Im Rahmen der selektiven Entwurmung wird nur die MDS-Eizahl pro Gramm Kot herangezogen und keine Larvendifferenzierung zur Identifikation der Strongyliden-Spezies durchgeführt (Nielsen et al 2006und 2014, Schneider et al 2014. Aus diesem Grund, wurde auch im Rahmen der eigenen Analysen auf eine Larvendifferenzierung verzichtet.…”