Utilization of composite fecal samples for detection of anthelmintic resistance in gastrointestinal nematodes of cattle

• Published in: Veterinary parasitology 2017-06, Vol.240, p.24-29
• Main Authors: George, Melissa M., Paras, Kelsey L., Howell, Sue B., Kaplan, Ray M.
• Format: Article
• Language: English
• Subjects: Animals; Anthelmintic; Anthelmintics - pharmacology; Cattle; Cattle Diseases - parasitology; Composite samples; Drug Resistance; Fecal egg count; Feces - parasitology; Gastrointestinal Diseases - diagnosis; Gastrointestinal Diseases - parasitology; Gastrointestinal Diseases - veterinary; Parasite Egg Count; Reduction test; Resistance; Specimen Handling - methods; Specimen Handling - veterinary
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/j.vetpar.2017.04.024

[Display omitted] •98.9% agreement in mean fecal egg count of individual and composite samples.•95.9% agreement in fecal egg count reduction of individual and composite samples.•Methods for conducting composite sampling were described.•Composite sampling is a practical tool for cattle producers to assess resistance.•This method may improve parasitological testing among producers. Recent reports indicate that anthelmintic resistance in gastrointestinal nematodes of cattle is becoming increasingly prevalent worldwide. Presently, the fecal egg count reduction test (FECRT) is the only means available for detection of resistance to anthelmintics in cattle herds at the farm level. However, the FECRT is labor and cost intensive, and consequently is only rarely performed on cattle farms unless for research purposes. If costs could be reduced, cattle producers might be more likely to pursue drug resistance testing on their farms. One approach to reducing the cost of the FECRT, is the use of composite fecal samples for performing fecal egg counts (FEC), rather than conducting FEC on fecal samples from 15 to 20 individual animals. In this study FECRT were performed on 14 groups of cattle using both individual and composite FEC methods To measure how well the results of composite sampling reproduce those of individual sampling, Lin’s Concordance Correlation Coefficient was utilized to describe both the linear relationship between methods and the slope and y-intercept of the line relating the data sets. There was little difference between the approaches with 98% agreement in mean FEC found between methods Mean FEC based on individual counts ranged between 0 and 670.6 eggs per gram of feces, indicating that the results of this study are applicable to a wide range of FEC levels. Standard error of the mean FEC and range of FEC are reported for each group prior to and following treatment to describe the variability of the data set. There was greater than 95% agreement in drug efficacy between individual and composite sampling methods, demonstrating composite sampling is appropriate to evaluate drug efficacy. Notably, for all groups tested the efficacy calculated by composite sampling was within the 95% confidence interval for efficacy calculated using individual sampling. The use of composite samples was shown to reduce the number of FEC required by 79%. These data demonstrate that pooling fecal samples from a group of cattle and then performing repeated FEC on that compos