Lejeune, M.; Mann, S.; White, H.; Maguire, D.; Hazard, J.; Young, R.; Stone, C.; Antczak, D.; Bowman, D. Evaluation of Fecal Egg Count Tests for Effective Control of Equine Intestinal Strongyles. Pathogens2023, 12, 1283.
Lejeune, M.; Mann, S.; White, H.; Maguire, D.; Hazard, J.; Young, R.; Stone, C.; Antczak, D.; Bowman, D. Evaluation of Fecal Egg Count Tests for Effective Control of Equine Intestinal Strongyles. Pathogens 2023, 12, 1283.
Lejeune, M.; Mann, S.; White, H.; Maguire, D.; Hazard, J.; Young, R.; Stone, C.; Antczak, D.; Bowman, D. Evaluation of Fecal Egg Count Tests for Effective Control of Equine Intestinal Strongyles. Pathogens2023, 12, 1283.
Lejeune, M.; Mann, S.; White, H.; Maguire, D.; Hazard, J.; Young, R.; Stone, C.; Antczak, D.; Bowman, D. Evaluation of Fecal Egg Count Tests for Effective Control of Equine Intestinal Strongyles. Pathogens 2023, 12, 1283.
Abstract
Parasite control strategies such as blanket anthelmintic treatment of all horses in a herd or interval treatment regimen based on egg reappearance remain widely followed practices for the last several decades. These practices have resulted in the fast emergence of resistance in equine strongyles to all major classes of drugs on the market. In this regard, the guidelines set by the American Association of Equine Practitioners advocate evidence-based strongyle control in horses. It recommends targeted treatment of all heavy egg shedders [> 500 eggs per gram (EPG) of feces] while the low shedders (0-200 EPG) are left untreated to maintain susceptible parasite refugia in a herd. As 50-75% of adult horses in a herd are low shedders, preventing them from unnecessary anthelmintic exposure is critical to tackling resistance. There are various fecal egg count (FEC) techniques with many modifications and variations in use, but none is identified as a gold standard and methods comparison studies are lacking. We hypothesized that the diagnostic performance of commonly used quantitation methodologies differs and the FEC methods must be evaluated to determine the gold standard. In this regard, we performed methods comparison studies using polystyrene beads with size and specific gravity comparable to strongyle eggs, as proxy. The linearity of 12 commonly used FEC methodologies (3 techniques with 4 different solutions) was studied using bead standards in the clinically applicable range (63 to 1,000) to determine their suitability for strongyle egg counts. Deming regression analysis identified Mini-FLOTAC with sugar (specific gravity 1.33) as the test with the greatest coefficient of determination. All tests underestimated the true bead count, and we determined a correction factor (CF) for each test to estimate the true count. CF negates the preference for a gold standard test. Finally, we analyzed the validity of CF for 5 tests with R2>0.95 to accurately quantify strongyle eggs from 40 different horses. Overall, this study identified methodologies with the highest diagnostic performance and the limitations to standardizing routine FEC tests to promote uniformity in implementing AAEP parasite control guidelines.
Keywords
Equine strongyle; Fecal Egg Count; FEC; modified McMaster; Mini-FLOTAC; Wisconsin floatation; sugar 1.33 specific gravity; NaNO3 1.33 specific gravity; NaCl 1.20 specific gravity; ZnSO4 1.18 specific gravity; AAEP; anthelmintic resistance; FEC gold standard
Subject
Biology and Life Sciences, Parasitology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
