Faecal egg count reduction test for assessing anthelmintic efficacy: average versus individually based estimations

Area of Science:

• Veterinary Parasitology
• Animal Health
• Pharmacology

Background:

• Faecal egg count reduction (FECR) is standard for evaluating anthelmintic efficacy against gastrointestinal strongyles.
• Current FECR methods can overemphasize high egg-shedding animals, potentially skewing efficacy results.
• Variability in FECR values arises from different calculation methodologies.

Purpose of the Study:

• To introduce and evaluate individual animal FECR methods for assessing anthelmintic efficacy.
• To compare the outcomes of individual-based FECR with traditional average-based FECR.
• To establish confidence intervals for individual-based FECR methods.

Main Methods:

• Two individual animal FECR methods were developed: one without untreated controls and one with untreated controls.
• Confidence intervals (P = 0.95) were calculated using bootstrap resamples for both individual methods.
• Comparison of individual-based FECR values against average-based FECR values.

Main Results:

• Individual-based FECR generally yielded lower efficacy values compared to average-based FECR.
• Individual FECR proved reliable for evaluations with egg counts exceeding 300 eggs/g.
• Reliable results were obtained when testing a minimum of 10 animals per group.

Conclusions:

• Individual animal FECR provides a more equitable and potentially more accurate assessment of anthelmintic efficacy.
• The proposed individual-based methods offer a robust alternative to traditional FECR approaches.
• Individual FECR is recommended for studies with sufficient animal numbers and baseline egg counts.