NSW WormBoss Worm Control Programs
NSW WormBoss Drench Decision Guides
Some big frosts and winter temperatures will have put a stop to Haemonchus development for the time being. Worm egg counts over the past month have generally decreased on the whole, however some high worm burdens continue to be identified.
Worm monitoring throughout the year (rather than limiting to peak pressure periods) enables worm management to be maintained at a consistently high level. This not only ensures that productivity loss due to parasitism is negligible but also potentially decreases drench use, particularly over the winter months.
Haemonchus continues to be the dominant worm species identified in most submissions from the New England/North West region, however Trich’s (black scour worm) have been seen at significant levels in the occasional mob, particularly weaners. Genuinely effective broad spectrum drenches are required in this circumstance. Knowing what drench products fall under this definition (and which don’t) on any given property is largely guesswork unless a recent (within 2 years) drench resistance test has been performed. I would urge all sheep producers to make genuine plans to conduct such testing over the next 6 months. Feel free to contact me at Veterinary Health Research for further advice on this subject.
Worm counts for our district have remained low. A few producers that had experienced high counts 6 weeks prior have re-tested their stock with numbers dramatically reduced. Numbers averaged from 0 epg–390 epg for this past month. Temperatures have fluctuated from frosty mornings and frigid nights the last few weeks to warmer days and nights this past week, but still not enough for infective larvae to take advantage of these conditions.
The last few days have brought in a good spot of rain to our eastern areas, which has brought smiles to all the producers out this way.
There could be trouble ahead for ewes about to lamb. One recent case involved deaths of aged ewes lambing on short, low quality pasture. They were fat when drenched six weeks ago, but had lost condition dramatically since. Heavy mixed burdens of barber's pole, black scour and brown stomach worms exacerbated the under-feeding.
While this is an extreme example, pastures are not as flash as many producers think, and fat, pregnant ewes risk significant weight loss. Some paddocks are carrying a heavy over-burden of dead grass, the result of excessive summer growth and recent heavy frosts. This shading has reduced new autumn pasture growth, and leads to 'patch grazing' where sheep return to heavily grazed green patches in a larger paddock. These patches often become hot-spots for sheep worms, with ewes less able to avoid picking worms up during late pregnancy and early lactation. Don't lamb ewes in paddocks that gave you worm trouble earlier in the year, or where weaners have grazed since Christmas, as worm contamination levels will remain high. Scanning results show that twinning rates are up this year, frequently as high as 60% twinners. So monitor ewe body condition scores in late pregnancy and be prepared to supplementary feed if pastures can't maintain ewe condition, to give them a fighting chance against worms.
Enquiries about sheep lice have increased in the past few weeks, with spring-shorn sheep starting to look rubbed. Producers are always quick to blame 'the neighbours' when they find lice. But in most of these recent cases, lice were present at the previous shearing, and have remained despite treatment. We are fortunate to have several very reliable lice chemicals available for use off-shears. "Treatment failures" usually turn out to be "failed to treat", because not all sheep are shorn and treated at the one time.
We are still seeing some high worm counts in the Monaro region despite the colder weather, most likely a result of still damp soils from Autumn rains and good pasture levels. Counts have ranged from 140 epg in wethers to 1600 epg in Merino weaners. Barber’s pole worms have mostly still predominated, although the scour worm counts are on the increase.
Fluke have been a problem as well this year as areas of paddocks that are not normally wet have become infested with fluke larvae with higher than normal creek and dam levels with the recent good rains. One producer lost around 60 ewes with symptoms of pale gums and sudden death. Assuming that barber’s pole were the cause he drenched for these. The sheep continued to die and on post mortem were found to have severe liver damage with haemorrhages and numerous fluke. A follow up drench with triclabendazole has improved the situation.
Worm tests are recommended at this time for any weaners that are not doing well, as well as for pre-lambing ewes. It is also time to ensure that clean paddocks are available for the ewes to lamb down on. Paddocks that have been cropped, spelled or grazed with a different animal type for the last 5 months are ideal.
Very few worm egg counts have been seen this month; residual sowing and concurrent lambing are likely responsible for this. Worm counts seen in the area still show significantly high proportions of barber’s pole eggs. We have seen Cooperia appear in very low levels in recent sheep tests. There is no need to alarmed, drenches that treat other round worms will also cover Cooperia.
Worm management advice is very similar to last month’s. If lambing has not started, a pre-lambing drench should be considered 2–3 weeks prior to lambing. This is particularly important for Merino weaner production systems, aiming to minimise the effects of worm burden on young sheep at weaning.
Consideration to weaning pastures and preparation should be well under way. Low risk grazing pastures include stubble or forage paddocks, paddock grazed by cattle for 2–3 months of summer or over 6 months for cooler months, or pasture not grazed by sheep younger than 18 months of age.
Consider drenching ewes and weaner lambs at 12–14 weeks post lambing and move onto low risk pasture. Early weaning at 12–14weeks of age is important to ensure early separation of two age classes reducing risk of egg exposure as well as nutritional competition; this has concurrent trade offs for return to joining weights in ewes.
Around the Griffith region there have been significant worm egg counts reaching 680 eggs per gram in young lambs. These eggs were from the thin-necked intestinal worm, which occurs in the major sheep producing areas of the country. Scouring and death will occur in young lambs if not treated. Prompt treatment (drench) is required in lambs when worm egg counts reach 200 eggs per gram. These worms commonly occur after dry summer periods when short green pick emerges.
Strongyle egg counts have also been on the rise around the Griffith area with counts of 480 eggs per gram; Trichostrongylus (black scour worm) makes up the bulk of the count. Treatment (drenching) is indicated when counts reach 150 eggs per gram in the non-seasonal rainfall region. Production loss can be significant before any signs of Trichostrongylus infection occur.
Even though many paddocks are sparse with feed, worm egg counts are also on the rise around Hay, Hillston and surrounding areas therefore using a ‘worm test kit’ is recommended.
We have seen the re-emergence of barber’s pole worm (BPW) as an issue this month, particularly in the east of the region. This includes a property where clinical BPW was diagnosed and treated with Zolvix 2 months ago. BPW infection became evident again this month as L3 larvae that hatched before the dry months continue to survive and be an ongoing source of infection for many months. In the west we have had problems with scour worms; a total worm count on an individual farmer’s property showed extremely high numbers of brown stomach worm and thin-necked intestinal worm (5000 of each).