NSW WormBoss Worm Control Programs
NSW WormBoss Drench Decision Guides
NEW SOUTH WALES
Worm pressure is high (to extreme) throughout most of the New England district at the current time. Rain events have generally been of sufficient frequency and magnitude to maintain constant worm development. Graziers operating under set-stocked conditions and/or unwittingly using ineffective drenches are under the greatest threat of sheep and production loss due to haemonchosis.
A number of properties in the Glen Innes district have performed drench resistance tests and/or post drench checks over the last month. Significantly, the only drench products with consistently high efficacy against Haemonchus have been Zolvix® and Startect®. This finding is consistent with VHR data showing that multiple drench resistance is commonplace on a large percentage of New England sheep properties. Graziers need to be made aware of this fact and encouraged to perform their own drench resistance testing.
Editor’s note: WormBoss has just produced the Combination-Drench Efficacy Calculator. In the past, deciding which drenches to test was an obstacle to doing a test. Now, with this calculator, the decision is simple. Test just the single actives described by WormBoss and then use the calculator to predict the efficacy of ALL combination drenches on your property.
Don't forget liver fluke
A northern NSW sheep producer recently had deaths caused by liver fluke and is now madly drenching all his sheep to prevent further losses.
They normally don't drench for liver fluke on this property because they rarely get confirmed deaths from liver fluke and are not aware it is a cause of ill-thrift.
They could be right of course, and it may not be economic for them to treat for fluke. However, as we know from roundworms, 80% of the losses to the Australian sheep industry from worms is from loss of production, much of which goes unnoticed unless you deliberately measure productivity, for example, growth rates. The situation is similar with liver fluke: most of the cost is from reduced productivity.
The deaths in this case followed a classic pattern. Rainfall of late had been below average, and the sheep were grazing in gullies and along creeks where there was 'green pick'. This was also the place for liver fluke.
This producer has a good vaccination program, so at least black disease, a clostridial disease which is associated with liver fluke infections, did not become an extra problem.
It would be a good idea for this farmer to test for liver fluke a few times a year. Testing around the usual times to treat for liver fluke—April, August and February—would be a good start, and then review the situation after a couple of years. Drenching all stock this April or May at least—when the cold weather starts—would be a good move too, especially if we get good rain in summer and autumn, which will increase numbers of liver fluke on pasture.
Worm burdens around the Condobolin district have been moderate to high in young stock ranging from 600–8,600 eggs per gram (epg). Some of these were related to investigations into ill-thrift, weight loss and death in lambs. On the few worm populations that were typed (by larval culture), mixed populations were found with majority being black scour worm.
Worm burdens around the Coonamble and Nyngan districts have remained low (as indicated by WormTest results) despite some sporadic storm activity. There have been no clinical cases of worms seen. Several mobs of lethargic and ataxic sheep reported in the north west were diagnosed as having humpy back from "Quena/Wild Tomato" or poisoning from "Flat Billy Button" rather than worms. A recent Worm Egg Count Reduction Trial ("Drench Test") performed near Gulargambone showed barber’s pole worm resistance to abamectin and BZ drenches. All producers are encouraged to continue to WormTest and drench strategically.
Worm egg counts have varied across the Dubbo district with some sheep flocks demonstrating low worm burdens and others having moderate to high burdens. Of the cases reported and seen, weaners and lactating sheep have been the most susceptible. The weaners investigated were doing poorly despite lush feeding conditions. Turns out, they had a triple worm infection consisting of black scour worms, brown stomach worms and thin necked intestinal worms. Surprisingly, no barber's pole worm, which is what we usually see this time of the year.
On another property consisting of lactating ewes (with no signs of ill-thrift), a routine check found average egg counts of 2,620 epg consisting of mixed burdens of barber's pole worm and black scour worm.
A routine check, however, on another farm in our district consisting of weaned lambs and their mothers found only low worm burdens present such that a drench was not required.
Bottom line: monitor your flocks this summer with worm egg counts to see whether a drench is necessary.
There have been few worm tests conducted recently. However, a small number have been carried out to investigate ill-thrift and weight loss in a few flocks. These have found reasonable worm burdens, with mixed species often present.
We have had a case of a producer experiencing large losses due to Nematodirus, with confirmation via a worm egg count and histopathology. Affected animals were either found dead (sudden death), or were found weak (+/- recumbency) and scouring (though not in all cases), and those that were noticed to go 'downhill' showed a rapid drop in body condition. Subsequent drenching with a triple combination drench has helped quell any further deaths and we are now working with the producer to ‘clean up’ the affected paddocks so that it doesn't occur again. The paddock where this had occurred had not had any stock present for several months; however the trigger for the hatchings seems most likely to have occurred following rainfall after several weeks of dry weather.
Another producer was experiencing losses in his mob of 4–5 month old weaned lambs. Lambs were found dead in the paddock, or died when stressed from mustering. An on farm investigation revealed moderate worm burdens in the abomasum and no significant findings beyond this. A worm egg count for the mob showed a count of approximately 600 epg. The mob was drenched with a combination drench and the owner has not reported any further losses to date.
Elsewhere in our region, worm egg counts have averaged 180–1,200 epg with lambs averaging around 500–600 epg and adult mobs averaging roughly 150 epg.
Most producers are mindful of worms causing production losses, and are undertaking routine surveillance in the form of worm egg counts on their respective mobs. We have emphasised the importance this can have, particularly to those producers who are looking to finish their lambs in the coming months. Drench rotations continue to be advocated to all producers.
So far this month in the Wagga area, internal parasite activity has been quieter than expected considering the WormTests received, and number of disease investigations involving significant parasite burdens just prior to the Christmas break. I suspect this is due to drier environmental conditions, summer drenching and the use of crop stubbles for grazing (clean pastures).
I emphasize the importance of drench efficacy at this time of the year when many producers are attempting to "clean out" their weaners as they may be shooting themselves in the feet by not knowing if their drenching has been an efficient exercise* (*95% reduction in worm eggs). You should be contacting your local veterinary adviser or district veterinarian if you have not checked the efficiency of the drenches you use on farm in the last few years.
Few, if any, worm egg count reports have come in for this district over the last month. There has been significant rainfall lately in patches and so we would expect barber’s pole (Haemonchus) to be doing well on pastures and in sheep during this period.
Continued decent falls will see bumper Haemonchus levels in Autumn, which we haven’t had for some years.
Results from worm tests done locally:
In the western part of the region this month there were no reported clinical cases of worms, and only a small number of worm egg count tests were conducted. However, the results were very interesting.
A group of weaned lambs had been drenched with a levamisole (clear) and fenbendazole (white) drench combination at the start of the month and then were tested after 10 days to see what worms remained. There was an average of 116 eggs per gram (epg) strongyle and 36 epg Nematodirus with the range of 0–320 epg strongyle and 0–360 epg Nematodirus. An analysis of the strongyle type eggs found that 70% were black scour and 30% were brown stomach worms. There was also a low level of tapeworm and coccidia in the sample. This result is not surprising as both the white and clear type of drenches have been used for a long time on farms and there have been many reports of resistance in scour worms to this combination.
Other results were for a group of mixed aged pregnant ewes. They had not been drenched since February 2015, at which time they were treated with a macrocyclic lactone. The average results of 96 epg strongyle and 0 epg Nematodirus, were below the threshold at which we would normally treat. However, the range for strongyle type worms varied from 0–480 epg which showed that averages can sometimes hide an individual with a high worm burden. The sheep with the higher reading was actually from a group of purchased sheep so it was decided to use a triple combination drench on these particular sheep to try and get rid of any resistant worms which could become a problem in the future.
Recent summer rain in the eastern part of the region should prompt producers to stay vigilant and monitor worm burdens through worm egg counts. There have been several cases of clinical disease investigated by district veterinarians, with large numbers of barber’s pole worm found on post mortem. One of these cases occurred in trade lambs that had been drenched with moxidectin on arrival, suggesting that treatment was not effective. Worm egg count results from the region have shown moderate to high strongyle burdens. The main type of worm found in the samples tested was black scour worm.
Several sheep producers got quite a New Year surprise from their latest worm egg count results. Some had such low worm egg counts in adult sheep six weeks prior that they elected not to give a first summer drench, while others had given a first summer drench when pastures hayed off, about two months previously.
Worm egg counts have risen dramatically to be now several thousands. Cultures have shown most of these worms to be barber's pole. The surprise is that the couple of light rainfall events we've had were not expected to have encouraged hatching of barber's pole eggs and survival of larvae, as it was pretty crisp under-foot. The usual observation in these mobs is that the bit of green pick on valley floors is being hammered by sheep, and that there is also the odd short green shoot amidst the dense, dry trash.
In a couple of cases, barber's pole worms have caused the odd sheep to drop out during mustering, with pale skin and occasionally bottle jaw. One of these mobs had been drenched only four weeks previously with abamectin, reminding us that barber's pole are increasingly resistant to abamectin used on its own. Deaths of a number of dorper lambs were also due to this blood-sucker, despite also being drenched with abamectin.
But not all worm trouble at present is barber's pole, and you can be occasionally caught out by relying on worm egg counts alone without worm typing. Young sheep are doing it tough at the moment, due to poor pasture quality. Dry pastures are low in protein and have poor digestibility, meaning many mobs of lambs have lost weight since weaning. One producer saw a rise in worm egg count in his weaners, and immediately presumed barber's pole. They were treated with levamisole, which had proved effective against barber's pole in this flock in the past. Some lambs died before they could be treated to remove their black scour and brown stomach worm burden. A similar situation arose in a mob of ewes on another property.
Blowflies have been pretty quiet since early summer, but are poised for a rapid build-up if we get a few storms. The speed of maggot invasion of any sheep carcass is phenomenal over the past few weeks, reducing it to a seething shell within days. Some of these maggots will be sheep blowflies.