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

Abstract

All around the world, intestinal helminths constitute one of the most prevalent life-long occurring infections and re-infections affecting all horse age groups. A range of parasite species among strongyles, ascarids, and tapeworms is known to have the potential to cause colic in horses. However, there is a lack of current scientific evidence on the actual relevance of helminth infection levels in the context of colic in horses kept during prevailing epidemiological conditions. Thus, a prospective case-control study on the occurrence of intestinal helminths in a total of 620 mainly adult equine clinic patients was conducted to investigate the association between colic and helminth infection. For each horse, a range of copromicroscopic, serological, and clinical data was obtained, in addition to a questionnaire on relevant anamnestic data, including previous anthelmintic treatment and husbandry. Using a FLOTAC-based copromicroscopic diagnosis, the highest infection rates were seen for strongyles (41.8%), followed by Anoplocephala perfoliata and Parascaris spp. (both 0.8%), with no significant difference between the two study groups. Employing a real-time PCR a 1.1% S. vulgaris DNA prevalence was found. Considerably higher seroprevalences were observed using S. vulgaris and A. perfoliata ELISAs, with 32.3% and 10.7%, respectively. It was noteworthy that no association concerning either serologic status was encountered with colic status. The shedding of strongyle eggs was associated with a 1.8-times increased risk of S. vulgaris seropositivity. Recent anthelmintic treatment was associated with the onset of colic, as animals who had received an anthelmintic during the previous week had a 2.4-times higher risk of signs of colic compared to those who had been treated at least eight weeks prior. Another noteworthy observation was that ponies were significantly less often affected by colic than warmbloods. The high S. vulgaris and considerable A. perfoliata seroprevalences encountered in this investigation should prompt veterinarians, farm managers, and horse owners to maintain consequent and effective worm control measures.

Occurrence of Strongylid Nematode Parasites on Horse Farms in Berlin and Brandenburg, Germany, With High Seroprevalence of Strongylus vulgaris Infection

“…The cut-off values for the rSvSXP-ELISA applied in the present study were 25 and 30%, which is a more conservative approach decreasing the number of false positives but also increasing the number of false negatives. High S. vulgaris seroprevalences were also reported in other studies (91,101), but are unexpected in light of surveys employing direct pathogen detection methods (14,15). The high number of serologically positive horses compared to the four horses tested S. vulgaris positive by realtime PCR may partly be due to the fact that early stages in the prepatency of the infection can be detected only with the ELISA.…”

“…The DNA samples positive in the pan-nematode PCR were further analysed using an S. vulgaris specific real-time PCR targeting a partial ITS-2 region initially described by Nielsen et al (48) as modified by Gehlen et al (91). As positive control, plasmid DNA containing the ITS-2 amplicon from S. vulgaris in the vector pSC-B-amp/kan (Aglient Technologies, Waldbronn, Germany) was used.…”

BEVA primary care clinical guidelines: Equine parasite control

“…Studies performed in Sweden after the introduction of restrictions on prescribing, revealed 61% prevalence at the farm level and 9.2% and 28% prevalence in individual horses 261,281 . In Germany, prevalence was 1.1% by PCR 277 and a further study in Denmark reported a prevalence of 9.2% 262 . IgG(T) antibodies to recombinant S. vulgaris antigen have been identified in 75.9%, 62.1% and 59.4% of horses from Denmark, Sweden and Kentucky, respectively 253,279,281 …”

“…However, when specific types of colic were compared, horses diagnosed with peritonitis showed significantly higher ELISA scores than matched controls, possibly secondary to S. vulgaris associated non‐strangulating infarction 261 . A second prospective case–control study with 620 horses showed 1.1% of horses were positive by RT‐PCR and 32.3% by ELISA, however, there was no association between serological status and colic 262 . A retrospective case‐series performed in Denmark following mandatory implementation of diagnostic led de‐worming revealed similar S. vulgaris antibody concentrations between cases and controls; however, horses with non‐strangulating intestinal infarctions were more likely to be seropositive (OR 5.33, 95% confidence interval [CI]: 1.03–27.76) 263 .…”

Highlights of recent clinically relevant papers

“…In this prospective case‐control study Heidrun Gehlen and colleagues in Germany, USA, Italy and the UK investigated the association between colic and intestinal helminth infection.…”