Association between large strongyle genera in larval cultures–using rare-event poisson regression.

This research investigates the statistical relationship between different large strongyle species in horses, notably S. vulgaris, S. edentatus, and Triodontophorus spp., using a modified Poisson regression approach. The findings suggest that the presence of S. vulgaris could indicate the presence of other large strongyle species.

Background

• Strongyle species are intestinal parasites found commonly in horses. They pose a significant health risk, particularly for S. vulgaris which can lead to serious vascular complications.
• Overuse of anthelmintic treatments (drugs used to expel parasitic worms) has led to the development of drug resistance in cyathostomins, a small strongyle species, while resulting in a significant reduction in the prevalence of large strongyles.
• The effectiveness of larval cultures, a technique used to detect the presence of S. vulgaris, is relatively low. Hence, research is needed to see whether the detection of other large strongyle species could indicate the presence of S. vulgaris.

Methodology

• The study utilized a modified Poisson regression, a statistical tool often used for the analysis of rare events. This was used to analyze associations between S. vulgaris infection and the simultaneous presence of S. edentatus and Triodontophorus spp.
• The data was gathered from 663 horses across 42 Danish farms. The individual prevalence rates of S. vulgaris, S. edentatus, and Triodontophorus spp. were found to be 12%, 3%, and 12% respectively.

Findings

• The study found significant statistical associations between S. vulgaris infection and the presence of both S. edentatus and Triodontophorus spp. in horses, with relative risks above 1 (indicating an increased risk).
• Specifically, S. edentatus was associated with the use of selective therapy on the farms. It was also negatively associated with anthelmintic treatment carried out within the six months leading to the study.
• These findings suggest that the detection of S. vulgaris in larval cultures could be interpreted as an indication of the presence of other large strongyles.

Implications

• The research suggests implications for diagnostics and intervention strategies used in anthelmintic treatment programs, potentially providing a more holistic understanding of strongyle prevalence in horses.
• Further studies can consider these findings to investigate the evolution of drug resistance in different strongyle species as well as the efficacy of different anthelmintic treatments.