Variation in Counts ofHaemonchus contortusEggs in the Faeces of Housed Sheep

Abstract

1. Evidence is given which confirms the hypothesis of Peters (1941) that nematode eggsin McMaster slides are distributed according to the Poisson series.2. No significant variation in egg counts due to the time of sampling was found in any of four sheep observed over a period of ten days.3. A significant negative correlation of egg concentration with faeces output was found in three of the sheep (in the fourth it was negative but not significant).4. The variation from day to day was relatively much less marked when the counts were expressed as total daily output than when expressed simply as eggs per gram.5. No significant correlation was found between egg concentration and the dry matter proportion of the faeces.6. A table derived from the Poisson formula is given to aid in the determination of the range of populations from which an egg count might reasonably have been drawn.