Figure 1

Frequency distribution of the natural logarithm of I . suis oocysts per gram of faeces [ ln ( OPG + 1 )] from pooled faecal samples of 314 litters in 55 herds . Faecal samples were collected from half of the piglets of each litter and then pooled, during their second week of life. OPG counts were determined by a modified McMaster technique.