The estimation of pooled-sample sensitivity for detection of Salmonella in turkey flocks

Aims: To investigate the effectiveness of pooled sampling methods for detection of Salmonella in turkey flocks. Methods and Results: Individual turkey droppings were taken from 43 flocks, with half the dropping tested for Salmonella as an individual sample and the other half included in a pool of five. A pair of boot swabs and a dust sample were also taken from each flock. The results were analysed using Bayesian methods in the absence of a gold standard. This showed a dilution effect of mixing true-positive with negative samples, but even with this the pooled faecal samples were found to be a highly efficient method of testing compared with individual faecal samples. The more samples included in the pool, the more sensitive the pooled sampling method was predicted to be. The sensitivity of dust sampling was much more sensitive than faecal sampling at low prevalence. Conclusions: Pooled faecal sampling is an efficient method of Salmonella detection in turkey flocks. The additional testing of a dust sample greatly increased the effectiveness of sampling, especially at low prevalence. Significance and Impact of the Study: This is the first study to relate the sensitivity of the sampling methods to the within-flock prevalence.