NSW WormBoss Worm Control Programs
NSW WormBoss Drench Decision Guides
The generally good rain in January has stimulated worm activity in the north of the state. The VHR Laboratory has identified some very high worm egg counts over the past few weeks, mean WECs in the order of 3–4,000 epg being seen on a number of occasions. Interestingly, no worm symptoms had been identified by the graziers in several of these cases, despite mustering and close observation. This highlights the fact that sheep may carry high worm burdens of Haemonchus without necessarily expressing clinical signs. Worm monitoring allows this condition to be identified and appropriate drenching conducted before a “crash” occurs.
A number of clients have maintained their sheep in a low-worm status despite the favourable environmental conditions for worms. The key to their success in nearly all cases has been the adoption of rotational grazing, combined with varying degrees of co-grazing with cattle. A case in point is a Walcha district property that has a mob of 4,500 ewes which have not been drenched for worms since mid-September. Their most recent monitor (mid Feb) showed that they had a mean WEC of only 80 epg.
A recent submission highlighted the importance of establishing the nature of the worm infection you are dealing with and being aware of the limitations of the various drenches. Lambs treated with naphthalophos and levamisole continued to be showing illthrift (and a number dead) one week post treatment. A worm egg count was performed, which confirmed a significant Black Scour Worm infection (mean WEC of 800 epg). It is not uncommon for such a drench combination to be largely ineffective against scour worms.
Now is the time for WormTests!!! (and second summer drenching only if required!)
Currently, most properties in the central Riverina submitting WormTests have shown modest worm burdens. Having said this, now is the time to seek advice concerning a second summer drench—there certainly have been cases to support this as a matter of importance: e.g. WEC >900 without any Barber’s Pole Worm larval growth. For this reason, in addition to the recent summer showers, I urge all producers to have a WormTest performed ASAP.
Worm species update:
Over the last 1–2 months there was a noticeable spike in the % of Barber’s Pole Worm burdens i.e. larvae cultured. This appears to have died off dramatically in the last few weeks, e.g. infectious of <5%. Current, predominant burdens are of the serial offenders: Black Scour Worm, Small Brown Stomach Worm and Large Intestinal Worm.
Worm counts in the Young area and surrounds have been a little variable.
Worm egg counts have varied from 0–560 epg. Larval differentiation on the few samples that it was requested for showed Ostertagia and Trichostrongylus species making up 30–40%. No signs of Barbers pole worm in any of the tests conducted thus far as well as no production losses reported by any producers (or worms being observed from disease investigations in the abomasum) from this worm species.
A recent series of rain events have occurred over the past few days, and we have reminded producers to be mindful of worms and to ensure that WormTests are conducted at regular intervals to ensure they stay on top of worm numbers on their properties.
Only a small number of WormTests have been conducted over the past month in the old Narrandera area. These have shown mixed egg counts ranging from 0 to 920 epg, with mixed worms present, including barber’s pole worm.
With scattered storms occurring across the area, there is the potential for barber’s pole infestations to become an issue in the autumn.
Producers are advised to monitor their sheep and seek advice on treatment.
Barber's pole worms continue to cause havoc on some properties and in some mobs. The problem is made worse where feed has become tall and rank and sheep are returning day after day to short-grazed green patches that quickly become heavily contaminated with worm larvae.
Drench resistance has started to ramp up too, with one producer losing six rams from barber's pole worms just three weeks after a 'triple' drench, and another with deaths continuing despite both a long-acting moxidectin injection and concurrent four-way combination oral drench!
Sending faecal samples for a DrenchCheck test 10–14 days after drenching would have identified that these drenches didn't work, and may have avoided the losses.
On the other hand, worm egg counts on a number of properties show very little worm activity. It is not uncommon to see near-zero worm egg counts on adult mobs last drenched in July '14. It's even hard to find those tail-end merino weaners that scour and die year after year.
History tells us our dream run can't last. The last time we had a cracking green summer/autumn followed by a dry winter we saw massive worm problems later that year in lambing ewes. The worst crashes occurred where lambing ewes were run in paddocks grazed by lambs/weaners the preceding autumn.
The point of the history lesson? Keep a record of where you graze your weaners this autumn, and reserve some paddocks now for future lambing, just in case.
Blowfly activity has abated, with less body strike (due both to a change in the weather and use of preventive treatments), but any bit of green scour on lambs and the pizzles of wethers appear prime targets.
The weather continues to promote grass growth and worms in the valley. Haemonchus is prolific and continues to catch some farmers out with its insidious effects and sudden impact in the form of deaths. The only way to really have some idea of where your flock is at in a season like this, is to do WECs around every 30 days—if you wait for a couple of months to check, or give another drench you may already have lost a few.
As always, from an economic point of view and with the commitment to not promote the development of resistance, over drenching is to be avoided. In a season like this, under-drenching can have dire consequences in the form of production loss and deaths. The answer is to do WECs—they are cost effective either way you look at it, and with sheep prices as they are, worth the small investment of time and money to take the guesswork out.