Poisson sampling: A sampling strategy for concurrently establishing freedom from disease and estimating population characteristics

Poisson sampling is an unequal probability sampling design that can provide efficiencies similar to targeted surveillance while allowing inferences for other population parameters. The adaptation of Poisson sampling to animal surveys is described. A simulation study, based on sampling a flock of sheep, is used to demonstrate the reductions in sample size that are possible with Poisson sampling. The study showed that the sample size required for a flock-level sensitivity of 0.95 when using Poisson sampling was less than half that required when using simple random sampling. The performance of estimators for prevalence of scrapie and distribution of genotypes are also compared.