Effects of daily pyrantel tartrate on strongylid population dynamics and performance parameters of young horses repeatedly infected with cyathostomins and Strongylus vulgaris.

This research investigates the effects of daily pyrantel tartrate treatment on horses repeatedly infected with small and large strongyle nematodes. The study finds that such treatment significantly reduces the nematode population and improves the body condition and weight gain of the horses, providing valuable insight into combating these common but understudied horse parasites.

Research Objectives and Methodology

• The main goal of this research was to examine the effects of daily pyrantel tartrate treatment on the population of small and large strongyle nematodes in horses and the corresponding impact on the horse’s health.
• Researchers conducted a masked, randomized, controlled study with 28 immature horses, which were divided evenly into two groups.
• The first group received a pelleted placebo daily, while the second group received daily doses of pyrantel tartrate based on body weight.
• Both groups were additionally infected with roughly 5000 small strongyle larvae five days each week, with approximately 25 large strongyle larvae being added weekly.
• Horse weights, body condition scores, fecal egg counts, and blood sample analyses were conducted approximately every 14 days.
• After 22 weeks in a pasture and 14–17 days in confinement, the horses were euthanized and examined for nematodes in their organs and intestine.

Research Findings

• Daily treatment with pyrantel tartrate significantly reduced the number of adult strongyle nematodes and larvae in the horses’ gut while also increasing the proportion of fourth-stage larvae in the gut contents.
• Horses receiving the treatment also displayed significant improvements in body condition scores, indicating overall enhanced health.
• The study observed a decrease in fecal egg counts in the treatment group, with an efficacy rate between 84.4% and 98.9%. However, egg counts in both groups rose progressively throughout the study.
• The number of large strongyle larvae in horses’ cranial mesenteric artery was significantly reduced by the treatment, with a reduction rate of 99.2%.

Conclusion

• The research shows that daily pyrantel tartrate treatment can effectively reduce the population of small and large strongyle nematodes in horses, thereby improving their health status.
• However, despite the reduction in nematode population and fecal egg count, there is an observed increase in both parameters over time, indicating a persistent source of infection.
• Despite the decrease, serological persistence of antibodies to large strongyle from pre-enrollment infections was observed, pointing to the possibility of persistent infection or reinfection.
• The study provides valuable insights into remedies for strongylid parasitism in horses and underscores the importance of control measures to prevent the spread of nematode larvae.