Helminth egg excretion with regard to age, gender and management practices on UK Thoroughbred studs.

This study explores the combined impact of factors like age, gender and management strategies on the prevalence of worm infection and egg shedding in grazing horses. The research was conducted on Thoroughbred horses living in the UK and revealed strong relationships between these variables and the level of worm egg excretion. Additionally, the findings support the idea that targeted treatments could form an effective part of controlling worm infections in horse populations.

Research Method and Sample

• The research was carried out using fecal samples from 1221 Thoroughbred horses living at 22 horse-breeding farms (studs) in the UK.
• The prevalence of worm eggs in the feces — referred to as the fecal worm egg count (FWEC) — was examined using a modified salt flotation method. This process quantified the number of worm eggs present per gram of feces.

Results and Findings

• FWEC prevalence was determined for four different species of worm — strongyles, Parascaris equorum, tapeworm species and Strongyloides westeri. The respective mean prevalence rates for these species were 56%, 9%, 4% and 8%.
• All tested studs saw at least some infections of strongyles, while only about half saw P. equorum infections. Less than half reported infections of tapeworm species and S. westeri.
• Within horses of all ages and genders, strongyle FWECs were highly variable. Across the horse population, the average FWEC was 95 eggs per gram of feces.
• Data analysis indicated that the horse’s age, the type of the last anti-worm medication they received, and particular management practices (such as how groups of horses are rotated for grazing) had the most substantial influence on the prevalence of strongyle infection and the level of egg shedding.
• Strikingly, a small proportion of horses — 11% — were found to be responsible for excreting 80% of the total strongyle egg count detected in the analysis.

Implications of the Study

• The patterns observed in this study point towards the potential effectiveness of targeted treatment strategies for controlling equine worm populations.
• By focusing treatment efforts on the individuals harboring high worm burdens, it’s possible to both protect those horses and foster a refugia, which is an environment where populations of worms that are susceptible to anti-worm medications can survive. This helps to prevent the onset of drug-resistance within the worm populations.