NSW WormBoss Worm Control Programs
NSW WormBoss Drench Decision Guides
Barber’s pole worm remains abundant well into the summer with the continued mild, wet weather in the district. Larval differentiations are showing concurrent infestation with trichostrongylus (black scour worm) in many cases. Consider this when selecting an appropriate drench. If you are concerned you may have drench resistance issues or are interested in what chemicals your worms are resistant to, then please enquire about drench resistance testing.
It’s important to start planning low-risk lambing and weaning paddocks now. The mild summer is likely to result in higher worm burdens on paddocks, so by resting for at least six months, this provides a low-risk paddock for the highly susceptible classes of sheep in late winter and spring.
Reports of flystrike resistance to dicyclanil continue. Incidences of shortened duration of protection is being described and resistance testing is underway. While testing in recent years showed a reduction of 69–78% in the duration of action from the manufacturer claims (Sales et al. 2020), we need to be considering management practices to not only deal with flystrike and the challenge of dicyclanil resistance but also to slow and reduce resistance to other chemical groups.
Some management practices include:
Reference: Sales, N, Suann, M, Keoford, K, ‘Dicyclanil resistance in the Australian sheep blowfly, Lucilia cuprina, substantially reduces flystrike protection by dicyclanil and cyromazine based products’, IJP: Drugs and Drug Resistance 14 (2020) 118–125
There is plenty of worm activity on farms with high worm egg counts and some dead sheep from barber’s pole worm seen near Gular last week. I am sure there are many more sheep out there that have a bellyful of worms but aren’t noticeably sick…yet!
Interestingly, it’s not just barber’s pole worm. Almost all of the WormTest results that I’ve seen lately show a fair mix of black scour worm as well. These are a hangover from a wet winter and spring, and they are surviving in the milder summer temperatures. Drench selections need to target both worms, otherwise they willstill be active into the cooler months and are likely to cause clinical disease in your stock.
Speaking of drench selections — there have been some drench trials done in the area in recent months, and the results for barber’s pole worm are alarming. To give you some examples of the results, moxidectin only worked on 40% of farms, abamectin did not work on any of the farms and closantel only worked on 50% of the farms.
The moral of the trials is that single active drenches are likely to be poorly effective —combinations are strongly recommended. Under the current climatic conditions, careful attention needs to be paid to keeping paddocks ‘clean,’ or free of worm larvae for susceptible classes of stock (lambing ewes and lambs being weaned). This means after preparing the paddock, drench those sheep with an effective combination drench before they move into the clean paddock. I see many people who have no available clean paddocks and so are looking to use long-acting drenches. There are so few of these on the market, we already know there is resistance on some farms, and overuse is going to speed up resistance developing on others.
Flystrike is still prevalent on farms and producers are again advised that there is significant chemical resistance. Difficulty sourcing shearers at the moment is also a challenge.
We are continuing to see issues with worms in the district. While barber’s pole is the main culprit killing stock at the moment, we are still seeing significant proportions of black scour worms on WormTests.
High worm egg counts (WECs) have prompted many producers to raise concerns about drench resistance, but on further investigation it often turns out that it has been too long between drenches or they have only used a knock down drench and then put sheep into paddocks contaminated with larvae. With the ideal conditions for worms at the moment, producers should be conducting WormTests on their high-risk stock every 4–6 weeks and drenching based on WECs. If there are only dirty paddocks available to move weaners into post-drenching, consider using a long-acting product concurrently with an effective “primer” drench and a “tail-cutter” knock-down drench at the end of the active period to reduce the risk of resistance developing.
If you haven’t done a drench resistance trial on your property in the last few years, we are recommending pre- and 14-day-post drenching WormTests to assess the efficacy of the product. Some producers have discovered they have resistance to their drenches only after they have contaminated all of their clean paddocks with repeated ineffective drenching. While resistance profiles are specific to individual properties, recent drench resistance trials around the district have found high levels of resistance on many farms to traditional single-active products (abamectin, moxidectin, closantel). While they are a bit dearer, products containing multiple actives or new actives (monepantel or derquantel) are much more likely to be effective and with the hot sheep market at the moment, the most expensive drench is the one that doesn’t work.
Since the New Year, the Forbes area of the Central West LLS has received above-average rainfall over several rainfall events. Days have been mild, and pasture growth has been good, creating an ideal environment for larval survival. February is also a time when producers should consider whether sheep will need a second ‘summer’ drench. Producers are advised to WormTest to determine if this is required. If the numbers indicate the need to strategically drench, then ensure you are reaching for an effective drench. The general rule of thumb is to avoid drenches that only contain single actives including from our newer drench groups and to rotate your drenches after a long-acting product or after using a prepared low worm-risk paddock. If you are preparing a paddock for winter weaners, the drenched sheep can be put onto these paddocks for 3 weeks only to help in preparation of low worm-risk paddocks. This drench may also coincide with a pre-lambing drench for those autumn lambing mobs. Conducting a WormTest 10–14 days after drenching will help monitor the effectiveness of your chosen drench.
The ongoing rain in the Nyngan district means that barber’s pole worms are thriving. In the last week I have diagnosed two cases of clinical barber’s pole worm in weaners and have seen many more concerning egg counts on WormTests. Farmers need to stay vigilant to the risk worms pose to their enterprise and should be worm testing their weaners at least every 4–6 weeks while the rain continues. Given the optimal conditions, I am even seeing clinical cases in dry adult sheep and thought should be given to protecting your rams from high worm burdens over the joining period.
Many farmers in the central west rely on spelling paddocks for a period to prepare them as lambing/weaning paddocks. Longer spelling periods and/or a smart grazing plan may be needed during this mild season to clean up your paddocks for high-risk stock. Smart grazing involves using dry adult sheep or goats to remove larvae from a paddock. The animals should be drenched with an effective short-acting product prior to introduction and removed 2–3 weeks later, before the larvae they have consumed have developed to egg-producing adults. Given the high numbers of barber’s pole in the district at the moment sheep should be removed at two weeks (18 days maximum), as the worms can have a slightly accelerated life cycle compared to other worm species.
Prolonged skin wetting from the recent rain events also means that some sheep are at an increased risk of fleece rot and body strike. Additionally, persistence of some fly preventatives is reduced with prolonged wetting, so farmers should remain vigilant for strikes. Shearing and crutching can provide up to six weeks protection from breech strike so, if possible, delay application of a preventative product for a month to get the most bang for your buck.
Producers in the central Riverina should be continuing to regularly monitor their flocks for worm burdens — conduct a WormTest at least every 4–6 weeks.
Recent WormTests in the area have shown mixed results, with patterns of higher eggs per gram in younger mobs, but also the presence of worms at production-limiting levels in adult ewes.
These have typically been mixed infection of both scour worms and barber’s pole worm, with affected mobs responding well to an effective drench.
Recent rainfall and excellent ground cover across much of the area means that worm and flystrike risk will continue — head to WormBoss, FlyBoss or contact your local district vet for assistance with making the best treatment decisions.
At this stage, worm egg counts from across the district have reflected only low to moderate burdens, with flocks occasionally returning over 200 eggs per gram. Summer rain and increased ground coverage may lead to elevated worm risk over the next month as we head into autumn. High worm burdens can occur alongside other diseases or toxicities, worsening losses and further reducing productivity. Producers must remain vigilant and continue to conduct regular WormTests to ensure early detection of worm burdens guide management decisions, and prevent losses. Despite favourable wet and warm conditions, barber’s pole worm numbers have not dominated so far this summer. Producers should remain on alert and monitoring for signs of bottle jaw, lethargy and pale gums. A few tests for liver fluke have been done in the west, but all have come up negative.
The end of summer has seen some irregular rain events across the district, which has resulted in germination of a variety of toxic weed species, including Hairy panic (Panicum effusum), cathead (Tribulus terrestris) and Common heliotrope (Heliotropium europaeum). Clinical toxicity can be seen where weeds are grazed in significant amounts, or over long periods of time, by susceptible stock. Avoid grazing stock, particularly young animals, on weed-dominant pastures. Keep an eye out for signs of possible poisoning including ill thrift, weight loss, photosensitisation (swollen or scabby ears and faces) and/or neurological signs.
Pneumonia and pleurisy are still being found around the district, often associated with rectal prolapses. Rectal prolapses are particularly an issue in sheep that have had the tails docked too short.
Rainfall totals for Braidwood in January were 117 mm, and at time of writing in February 29.8 mm. January maximum temperatures ranged from 15.2–37.3 degrees C, with an average maximum of 25.8 degrees C.
These conditions are very suitable for our three main sheep and goat roundworms’ eggs — barber’s pole (Haemonchus contortus), black scour worm (Trichostrongylus spp) and brown stomach worm (Teladorsagia [Ostertagia] circumcincta) — to hatch and become infective larvae.
Over summer, most sheep and goat producers in the south east have focussed their control on barber’s pole worm. Many producers chose a closantel and mectin combination treatment as their summer drench, hoping to achieve persistent barber’s pole control and to limit pasture contamination with barber’s pole eggs. Closantel is a narrow-spectrum drench, providing control of barber’s pole worm but not scour worms. Resistance of scour worms to abamectin (commonly the second chemical in closantel combination drenches) is common, with brown stomach worm resistance thought to occur on 30% or more of farms in non-seasonal to winter rainfall areas of south-eastern Australia.
A risk with this approach is that black scour and brown stomach worm are overlooked until suddenly scouring, weakness, collapsing and deaths occur, and emergency drenching is required. At that point there will already have been significant production losses.
I recommend a WormTest Gold with Larval Culture to get an overview of the relative proportions of the three worm species on your property. At the EMAI State Veterinary Laboratory, this test costs around $80 ex GST.
Another consideration with closantel is its persistent duration of effect. Persistent treatments increase selection for resistance. This is because as levels of the chemical drop over time, worms are more likely to survive the chemical. They then pass on genetic survival traits to the next generation of worms.
Local WormTests have shown resistance of barber’s pole worm to closantel on some properties. One local property had an average count of 1180 eggs per gram (epg) (96% haemonchus) in Merino weaners when tested six and half weeks after drenching with a closantel/abamectin combination. As label claims assert a six-week sustained activity, this did not immediately alert the producer to a concern. However, this mob was subsequently drenched with the same product again, and 14 days into the expected six-week protection period the mob had an average of 1580 epg (95% haemonchus). Effective drenches tested 14 days after treatment should have a worm count 98% lower than the pre-treatment count.
Ideally one should never drench repeatedly with a persistent treatment. A primer drench of a known effective drench group is strongly recommended concurrently with any persistent treatment. An exit drench (also called a “tail cutter”) should also be given two weeks after the end of the protection period of a persistent drench. Primer and exit drenches should be short acting drenches of a different drench group to the persistent chemical. Levamisole-based drenches are a good option, unless you have known barber’s pole resistance to levamisole on your property. If paddock contamination with worms is a problem, seek advice from a veterinarian or advisor before repeating long-acting treatments.
I can not stress enough how important it is for you to monitor your worm levels now with a worm egg count (WEC) and worm type/larval culture and then continue to monitor monthly into autumn.
WECs are very variable farm-to-farm and paddock-to-paddock, with average counts ranging from 100 to 7000 eggs per gram.
Rainfall and temperatures are ideal for worm numbers building, and sheep may be condensing their grazing into patches of pastures where it is short and green. Worm numbers can increase rapidly in these conditions. Conditions will continue to be ideal into the autumn, meaning that we will need to utilise effective drenching and pasture rotation to minimise the build-up or large larval numbers on the pasture.
Now is also the time to monitor for fluke, note that you have to request this test separately.
For many years in Yass, we have not really needed to worry about fluke, except on some marshy properties. However, this autumn after a full year of full or nearly full soil moisture profiles, fluke numbers are really on the increase, as evidenced by positive samples at the lab. Fluke can cause bottle jaw, anaemia, weight loss, diarrhoea and death, and are best monitored for and controlled before they cause liver damage.
Cattle producers might ask the vet to collect some (10) bloods for pooled fluke ELISAs at pregnancy testing to gauge the need for fluke control in the cattle.
Sheep producers can also use the blood test or request the faecal test when screening for worms.