2.3.3. Statistical analysis
The number of pigs sampled per herd (20) permitted to detect with 95% confidence a minimum prevalence of 10%. The proportion of qPCR positive pigs and seropositive pigs within a herd between the different time points was analyzed using McNemar tests. The values of the qPCR testing at the different ages within each herd were analyzed using repeated measures analysis of variance,with age at sampling as within variable. A logarithmic transformation was first applied to the qPCR results to normalize the data.