Cumulative prevalence achieved at each round of screening of blood samples taken from thirty-five African zebu cattle. The figure shows the plot of the cumulative prevalence (upper curve) for all species of trypanosome at each round of screening of the thirty five blood samples. As the number of screenings increases the cumulative prevalence also continues to increase as new samples are found positive. The cross sectional prevalence at each round of screening is also shown (lower curve). The mean cross sectional prevalence across all screenings is shown by the dotted line (9.7%).