Paul Nilon, Nilon Farm Health, Tasmania (firstname.lastname@example.org):
Around the northern midlands water is lying on the ground and pastures are still a bit short for twin bearing ewes. Not a disaster, but the nutritional shortfall and wet conditions are ideal for kickstarting Trichs, as evidenced by the sheep with tell-tale scour and a few PM results. At this time WECs are notoriously unreliable. Mature ewes may well have low to average WECs but part of the mob are carrying large burdens which are not laying many eggs.
As always, don’t just look at WECs: get out of the office to look at the sheep. Most young sheep have come through winter maintaining reasonable body weights. Their worm burdens will trigger their immune system and throw off worm burdens as spring progresses. From Sept onwards I suggest that the trigger for a drench be extended a bit (say, from 300-500epg) to allow their immune system to be primed. Again, don't rely on this if the available feed is short or if the weaners are scouring.
Finally, properties with heavy fluke burdens should be planning for a spring strategic drench.