Preserving new anthelmintics: a simple method for estimating faecal egg count reduction test (FECRT) confidence...

Area of Science:

• Veterinary Parasitology
• Drug Resistance Studies
• Statistical Modeling in Animal Health

Background:

• Anthelmintic drug classes have not seen new introductions in 30 years, increasing the risk of resistance.
• Effective nematode control in livestock is challenged by the development of anthelmintic resistance.
• Optimizing treatment strategies is crucial to preserve the efficacy of existing anthelmintics.

Purpose of the Study:

• To review and recommend management practices for slowing anthelmintic resistance.
• To identify optimal treatment strategies using simulation models for sustained nematode control.
• To introduce a novel statistical method for accurately estimating anthelmintic efficacy.

Main Methods:

• Simulation modeling under Australian conditions to test treatment strategies.
• Review of recommendations for delaying anthelmintic resistance and providing refugia.
• Development and application of a binomial proportion method for calculating confidence limits of faecal egg count reduction.

Main Results:

• A rapid rotation between "triple-combination" products and monepantel proved a successful low-risk strategy.
• Maintaining up to 4% of adult sheep untreated (refugia) effectively reduced resistance selection risk.
• The novel binomial method provides a more accurate estimation of anthelmintic efficacy, especially for high efficacy drugs, with 99% confidence limits recommended.

Conclusions:

• Strategic drug rotation and refugia are key to managing anthelmintic resistance in sheep.
• Accurate efficacy estimation using the new statistical method is vital for selecting effective anthelmintics.
• This approach helps preserve the longevity of anthelmintic drugs against parasitic nematodes.