Observations on equine strongyle control in southern temperate USA

Area of Science:

• Veterinary Parasitology
• Equine Health
• Anthelmintic Resistance

Background:

• Rotational anthelmintic treatments at eight-week intervals were ineffective for equine strongyle control in a southern USA stable.
• Benzimidazole resistance rendered certain treatments ineffective, and treatment intervals were too long to prevent ova contamination.

Purpose of the Study:

• To evaluate the efficacy of different anthelmintic treatment intervals for equine strongyle control.
• To assess the impact of environmental factors on strongyle ova-larval transmission in southern temperate USA.

Main Methods:

• A program of rotational anthelmintic treatments was implemented.
• Ivermectin treatments at eight-week intervals and pyrantel pamoate treatments at four-week intervals were compared.
• Equine strongyle egg counts were monitored.
• Environmental conditions influencing ova to larvae translation were assessed.

Main Results:

• Ivermectin at eight-week intervals and pyrantel pamoate at four-week intervals effectively reduced strongyle egg counts during the summer grazing period.
• Ova to larvae translation was most efficient in autumn and winter, with minimal translation during summer.
• Meteorological conditions during summer limited pasture infectivity, complementing anthelmintic effects.

Conclusions:

• Anthelmintic resistance is a significant challenge in equine strongyle control.
• Shorter treatment intervals with effective drugs like ivermectin and pyrantel pamoate can improve control during grazing seasons.
• Environmental factors play a crucial role in parasite transmission, influencing the overall effectiveness of control strategies.