1.   Nematode eggs differ greatly in size and shape, and the shell is of variable thickness usually consisting of three layers.

2.   This refers to an increase in the numbers of nematode eggs in the faeces of animals around parturition.

3.   The PPR is very marked in ewes and is the most important cause of pasture contamination with nematode eggs in the spring.

4.   Most sheep graze throughout their lives so that pasture contamination with nematode eggs and the intake of infective larvae is almost continuous and modified only by climatic restrictions.