Foals raised on pasture with or without daily pyrantel tartrate feed additive: comparison of parasite burdens and host responses following experimental challenge with large and small strongyle larvae.

The research investigated the effectiveness of pyrantel tartrate treatment in managing parasite burdens in foals raised on pastureland. The study found that while the treatment effectively reduced some forms of parasitic infections, it failed to prevent large strongyle infections and subsequently increased sensitivity to future parasitic challenges.

Methodology of the Study

• In this experiment, three groups of foals were considered, each maintained under different conditions.
• The foals in Group 1 and Group 2 were reared with their dams on pasture, while the foals in Group 3 were reared under parasite-free conditions.
• The daily feed for Group 1 included a serving of pyrantel tartrate – a common equine dewormer, while Groups 2 and 3 only received regular pelleted feed.
• Upon weaning, Groups 1 and 2 were moved to a heavily contaminated pasture for five weeks where Group 1 continued receiving the pyrantel tartrate treatment.
• Following this period, all the foals were moved into box stalls. They were divided into two sub-groups: one, which was challenged with a mix of different larvae types (varying species of parasites) and a control group.

The Results

• The study found that the daily dosage of pyrantel tartrate treatment in Group 1 reduced ‘cyathostome’ (a type of small strongyle worm) infections in both the foals and their dams. It was also successful in lessening exposure to infective larvae present on the pasture.
• However, this treatment was incapable of preventing infections from large strongyle parasites during the weaning period.
• Importantly, the Group 1 foals, despite the treatment, were found to be more susceptible to parasitic challenges when compared to the untreated group (Group 2) and comparably susceptible as the Group 3 foals (who were raised in a parasite-free environment).
• The Group 2 foals showed no disruptions following the parasitic challenges, which could be an important observation in understanding the impact of pyrantel tartrate treatment versus no treatment.

Conclusion

• The research suggests that daily pyrantel tartrate does have an effect in reducing certain types of parasitic burdens in pasture-reared foals.
• Despite the positive effects concerning small strongyles, it does not provide a complete solution to equine parasite management, particularly against large strongyle infections.
• The research also suggests that there could be an increased sensitivity to future parasite challenge following continuous treatment with pyrantel tartrate. This highlights the importance of a balanced parasite control strategy. Further study is required to determine the long-term implications of such daily treatments.