WA WormBoss Worm Control Programs
WA WormBoss Drench Decision Guides
Sheep parasite control has now reached a typical early-winter pattern, with the start of westerly cold fronts bringing rain when we usually expect it. As we all know, the difference is the early germination, with crops emerging and some excellent pasture growth. Touch wood, this could be a great year for agricultural production in WA.
However, it could also be a severe worm year unless worms are well and truly on the radar. The main recommendation now is to keep a lookout for worm problems earlier than usual and to monitor worm egg counts in sheep.
Ewes: Worm egg counts need to be low ahead of lambing, so the ewes aren’t held back by worms as they start lactation, and so lambs are not faced with heavy worm challenge from worms cycled by the ewes.
Most ewe flocks have positive counts by this time of year, unless they were given the recommended autumn drench within recent weeks. However, we’ve seen cases where ewes had close to zero counts, even though not drenched for months—it’s very hard to predict.
Action: Check worm egg counts a couple of weeks from when the lambs are due, and drench if these are over 100 eggs per gram. If a drench is needed, give it about 2 weeks out from lambing.
Otherwise, give a pre-lamb drench as a routine. Ideally, this is after worm egg count checks in past years have shown that most ewe mobs do need this drench under the particular management system.
Weaners (blue tags) and hoggets (red tags): Reports for the age groups are very variable—we’ve seen some very high worm egg counts, with drenching needed immediately, and some quite low counts. It generally gets back to the effectiveness of drenches in summer, but is also hard to predict.
If you see scouring in more than 5–10%, a drench to the mob is usually worthwhile. This indicates that the weaners have worm contact (picked up larvae off the pasture), and the scouring is a result of their immune reaction to this. Some may have significant worm burdens, some may not, but experience shows that a drench generally stops the scouring.
Monitoring of worm egg counts should continue at 4–6 week intervals, especially if growth rates or body condition is lower than anticipated.
Barber’s pole worm: As with last month, we’ve seen further outbreaks and sheep losses. The potential for this will continue until mid-winter, especially in lambs.
However, the biggest barber’s pole risk in the next few weeks will be in lambing ewes. These temporarily lose their worm immunity during lactation and can develop large worm burdens—if it is barber’s pole worm, it can be lethal. A pre-lamb worm egg count check will indicate whether a drench is needed and whether a long-acting treatment against barber’s pole worm is specifically necessary.
Blowfly strike: The risk is subsiding rapidly with cooler conditions, as the period where daytime temperatures are sufficient for larval development reduces. However, where there are dags there will be the risk of strikes, so an eye should still be kept out.
Recently there were good rainfall events and now seeding is under way. This week has been sunny with temperatures in the low to mid 20s—good weather if you are a worm.
Ewe counts in the last few weeks have been in the 110–150 epg range with drenching recommended.
We saw one case of Haemonchosis (barber’s pole) from a property west of Esperance. This was in a mob of ewes due to lamb in 6 weeks time. Drenching with closantel controlled the worms and there were no further deaths. It was recommended that these ewes be also drenched with a broad-spectrum drench, two weeks pre-lambing.
A few clients have had lambs with joint-ill. This has mainly been in bottle-reared lambs who may not have got colostrum. The recent wet weather may also have contributed to contamination of the umbilicus in these cases. Bottle-reared lambs with possibly poor immune systems will be more susceptible to the effect of worm burdens as they start grazing. Barber’s pole, which proliferates when the host’s immune system is suppressed, can rapidly become a problem. Worm monitoring and good pasture management is important.