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

Abstract

Background Strongylus vulgaris has become a rare parasite in Germany during the past 50 years due to the practice of frequent prophylactic anthelmintic therapy. To date, the emerging development of resistance in Cyathostominae and Parascaris spp. to numerous equine anthelmintics has changed deworming management and the frequency of anthelmintic usage. In this regard, reliable detection of parasitic infections, especially of the highly pathogenic S. vulgaris is essential. In the current study, two diagnostic methods for the detection of infections with S. vulgaris were compared and information on the occurrence of this parasite in German horses was gained. For this purpose, faecal samples of 501 horses were screened for S. vulgaris with real-time PCR and an additional larval culture was performed in samples of 278 horses. A subset of 26 horses underwent multiple follow-up examinations with both methods in order to evaluate both the persistence of S. vulgaris infections and the reproducibility of each diagnostic method.ResultsThe real-time PCR revealed S. vulgaris-DNA in ten of 501 investigated equine samples (1.9%). The larval culture demonstrated larvae of S. vulgaris in three of the 278 samples (1.1%). A direct comparison of the two methods was possible in 321 samples including 43 follow-up examinations with the result of 11 S. vulgaris-positive samples by real-time PCR and 4 S. vulgaris-positive samples by larval culture. The McNemar’s test (p-value = 0.016) revealed a significant difference and the kappa values (0.525) showed a moderate agreement between real-time PCR and larval culture.ConclusionsThe real-time PCR detected a significantly higher proportion of positives of S. vulgaris compared to larval culture and should thus be considered as a routine diagnostic method for the detection of S. vulgaris in equine samples.

Comparative Analysis of Intestinal Helminth Infections in Colic and Non-Colic Control Equine Patients

“…In contrast to previous studies reporting a less than 2% S. vulgaris prevalence in Germany using larval culture or DNA-based copromicroscopic methods [ 10 , 16 ], the high S. vulgaris seroprevalence of 32.3% was unexpected and is also astonishing in view of the herein calculated overall fecal S. vulgaris DNA prevalence of 1.1%. However, this is actually less than the 62.2% reported in the only other European field investigation of S. vulgaris sero-prevalence published recently by Scandinavian colleagues [ 36 ], who, in a very similar approach, compared gastro-intestinal parasite infection with intestinal disease status in a total of 259 horses.…”

“…According to the most recent available copromicroscopic German and international study findings, the cyathostomins to date occur almost ubiquitously amongst the strongyles and certainly at much higher rates than large strongyles such as S. vulgaris . The latter apparently occur only in very few horses and farms [ 10 , 11 , 12 ]. This is, however, not necessarily always the case, as recent Scandinavian studies have documented S. vulgaris farm prevalence of sometimes even over 60% [ 13 , 14 ].…”

Investigating the Strongyle Populations, with Emphasis on Strongylus vulgaris (Nematoda: Strongylidae) in Romanian Horses, Based on Larval Cultures

“…Different surveys showed that the S. vulgaris species is more commonly found in working horses, as it was in the present study, or in horses from farms where anthelmintic treatments are iregularly administered or with a lower intensity (Kyvsgaard et al, 2011). Therefore, due to the intensive anthelmintic treatment regime in the last decades, S. vulgaris is reported now in lower prevalence in well managed farms (Kaplan, 2002) as it is in Switzerland, Germany (Kaspar et al, 2017). In Poland, in slaughtered horses was of S. vulgaris was the most dominant nematode (22.8%), followed by S. edentatus (18.3%) and S. equinus (1.7% ) (Studzińska et al, 2012).…”

Prevalence of Strongylus vulgaris in horses after ten years of prescription usage of anthelmintics in Sweden

“…Similarly, in Denmark a higher prevalence of S. vulgaris was observed on farms using selective treatment compared to farms deworming on a regular basis ( Nielsen et al, 2012 ). In contrast, low prevalences of S. vulgaris (0.2–1.3%) have been reported from Germany ( Schneider et al, 2014 , Kaspar et al, 2017 ). However, selective treatment is not implemented as strict in Germany compared to Sweden and Denmark and many horses are still routinely dewormed ( Schneider et al, 2014 ).…”

“…More importantly though, in this study were all samples analysed individually compared to pooled samples from four horses in 1999 ( Lind Osterman et al, 1999 ). In addition, was S. vulgaris diagnosed with a specific PCR, which is considered to be a more sensitive method than the traditional morphological identification of harvested larvae from cultures ( Kaspar et al, 2017 ). However, a relatively recent study from Denmark also found a high prevalence of S. vulgaris although the results were based on morphological identification of larvae ( Nielsen et al, 2012 ).…”