AWWA WQTC52960

Three years worth of neonatal mouse infectivity data reflecting Cryptosporidiumoocysts obtained from 10 calves were analyzed to quantify the variation in oocyst viability. The annual mean ID50 ranged from 69 to 145 oocysts over the three year period with much greater lot-to-lot variation within each year. The majority of individual ID50 values from each lot fell within the 80% prediction limits of the combined logit dose response function for the three year period. This analysis emphasizes that the neonatal mouse infectivity assay is useful for measuring log scale changes in oocysts viability. It should be used with caution and with appropriate untreated controls, especially when attempting to measure less than log-scale changes in oocyst viability. Includes 4 references, table, figure.