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New South Wales worms, flies and lice update - May 2021

NSW WormBoss Worm Control Programs

NSW WormBoss Drench Decision Guides






Central West LLS

Condobolin: Hanna Thomas, DV (

In the Condobolin district, very few WormTests have been conducted over the last month. Those that were performed have shown low numbers in adult sheep with some moderate-high counts coming back in weaner lambs. Larval typing in these cases have shown fewer barbers pole worm numbers and an increase in scour worm numbers.  

Weaner lambs have low natural immunity and are stressed by the process of weaning, which means they are more susceptible to worms. This can also be amplified when nutritional needs are not met. This is why the weaner drench is considered a priority drench.  

Coonabarabran: Kate Atkinson, DV (

The change in season is likely to mean a change in worm dynamics favouring black scour worm so it is recommended to perform a larval culture with your worm egg count to ensure you are selecting the most appropriate and effective drench for the job. Remember when collecting faeces for larval culture that these samples be kept at room temperature (not refrigerated) to ensure successful incubation in the laboratory. 

Coonamble: Jillian Kelly, DV (

Winter is almost here and we have had some rainfall which is good for cropping and lambing plans. In terms of sheep worms, this means that we are heading out of the barbers pole worm risk period, and into the black scour worm risk period. A WormTest now with larval typing will provide very useful information for the winter management of your sheep.

Several WormTests seen from Gulargambone, Quambone and Coonamble lately have shown a real mix of worms, with both barbers pole worm and black scour worm present. While black scour worms typically don't love our hot, dry, summers; this year they have persisted - probably because it was milder and wetter, with a thicker grass canopy than what we have experienced over recent years. As a result, they are hanging around in flocks waiting for ideal wintery conditions to cause clinical problems. Remember, some of the drenches that are known to be quite effective for barbers pole worm are not effective for black scour worm (eg levamisole), and vice versa (eg abamectin). So don't guess, do a WormTest (with a larval culture) and use combination drenches wherever possible. Reaching for the wrong single active this winter could spell disaster later down the track.

There is still some blowfly activity occurring and producers are struggling to get shearers for crutching and shearing. While the incidence of flystrike will decrease over winter, be prepared for re-emergence in spring. Go to the FlyBoss website to devise an integrated flystrike management plan before the risk period arrives. 

The widely held belief that you must treat cattle for lice on the first frost is contributing to the development of anthelmentic resistance in internal parasites in our cattle herds. Drench trials performed in the Coonamble district in 2014 showed mild levels of resistance, especially to the older mectin compounds. Producers are advised to treat for lice only if the animals are severely affected and it is really warranted, and to consider the effect that the treatment will have on internal parasites. For more advice on this, or any topic give your District Vet a call!

Forbes: Nik Cronin, DV ( and Belinda Edmonstone, DV (

With lambing across our district well underway, producers are strongly advised to conduct pre-lambing worm tests to determine the best approach to manage ewe worm burdens. Pregnancy and lactation suppress the ewe's immune system causing the 'periparturient egg count rise', making them the second most susceptible class of sheep to worms. If not managed, this will impact the ewe's production/performance over lambing, but then also pose a problem for the lambs, with potentially high pasture larval contamination an issue when they commence grazing. 

Worm test results seen so far this season have reflected the mild, wet summer conditions that we had, with frequent significant egg counts and often a mix of worm types - both barber's pole and scour worms have been present on larval culture. Mixed worm populations mean that in most cases the best choice of drench will be a multi-active with two or more drench chemicals included. A short acting drench onto a clean, prepared lambing paddock is ideal, avoiding the risk of drench resistance development with a long-acting product. 

Where pre-lambing preparation has not been ideal, it may be a good idea to collect samples after lambing has finished to monitor ewe egg counts, to decide if a drench is required at lamb marking. A significant worm burden at this time means it will be important not to delay weaning, and the all-important weaning drench.  

Murray LLS

Albury: Mark Corrigan, DV ( and Eve Hall, DV (

On the sheep front, those approaching lambing are reminded that pregnant ewes are particularly susceptible to worm burdens given the reduction in worm immunity that occurs in late gestation. WormTests will help guide decision making. The worm egg count (WEC) threshold for pregnant ewes is slightly lower than standard thresholds: single-bearing mobs with WECs of >150 eggs per gram (epg), and multiple-bearing mobs with WECs >50-100 epg, generally warrant drenching. 

A quick refresher on good-practice drench use: 

  • WormTest - avoid unnecessary drenching. 
  • Use effective drenches and multi-active combinations where possible. 
  • In general, use short-acting drenches and restrict the use of long-acting drenches only for specific purposes. 
  • If the use of a long-acting is deemed necessary, don’t forget the need for primer and exit drenches.  
  • Calibrate your drench guns, dose to the heaviest sheep, and follow label instructions. 

Now is the time cattle producers might consider routine testing for liver fluke to help establish the infection status of their property. The two main tests include liver fluke egg counts on manure samples which help to determine whether the parasite is present, however can sometimes be unreliable as fluke egg shedding can be intermittent, and liver fluke antibody testing on blood samples which give an indication of the level of exposure to the parasite.   

April-May is generally considered the most important strategic fluke drench in southeast Australia. At this time, burdens may be heavy and made up of a mix of adult and immature fluke. This means a triclabendazole-based drench (ideally an oral formulation and optimally triclabendazole plus oxfendazole) is the treatment of choice.  

The good recent seasons have seen cows hold condition well over the summer and many beef producers across the region have been weaning calves a little later than in previous years. Calves should be strategically drenched at weaning and monitored with WECs every six or so weeks thereafter. WEC monitoring is relatively accurate in younger stock up to about 12-18 months age. From around two years of age most cattle are expected to have developed some natural immunity to worms. Try to opt for oral or injectable cattle drenches where possible. ParaBoss has a handy annual cattle parasite program guide for both spring and autumn calving herds in this region. Those looking to graze young cattle on winter crops should ensure a clostridial vaccine (pulpy kidney) booster is given a few weeks prior to the transition, and it is highly worthwhile giving additional boosters every 6-8 weeks while on good, lush feed.   

Deniliquin: Scott Ison, DV ( and Linda Searle, DV (

Many sheep producers in the west of the Murray region have already started or are just about to start lambing.  

Ewes should be in good condition and on good feed. This is important to ensure that ewes can cope with the nutritional stresses of late pregnancy, lambing and lactation. It is also a good indicator that the ewes are not being negatively impacted by worms. The most common types of worms we see in our area are scour worms, so poor condition and scouring are the key signs to look out for.  

Late pregnant ewes also have a large demand for calcium in their diet. Ewes being supplementary fed grain should be given a lick containing calcium - either a commercial block or a simple homemade lick consisting of salt and lime. Those on lush green feed should also be supplemented with magnesium to prevent grass tetany. 

South East LLS

Braidwood: Lou Baskind, DV (  & Amy Underwood, Charles Sturt University, Veterinary Science, final year student

Over the first 20 days of May, sunny Braidwood has received 117mm of rain, with the bulk of this falling across four days at the start of the month.  Mean daily temperatures have ranged between 5°C to 16°C and are trending downwards as we head into to winter. Rainfall for May thus far is well above Braidwood’s May average of 40mm. The soil profile at Braidwood is fully saturated, creating favourable conditions for pasture growth. Most pastures are green and growing actively, although a couple of recent hard frosts have browned things off a little.

As daily maximum temperatures until now have been over 15°C, worms have remained active. Worm egg counts (WEC) over the last month have varied but numbers have consistently been high and a mix of barber’s pole, black scour and brown stomach worms.

Daily maximum temperatures have just dropped below 15°C, so hatching of barber’s pole worm will stop and black scour worm eggs in the dung will slow right down (Trichostrongylus colubriformis tends to stop below 15°C, but T. vitrinus can continue down to 12°C). But brown stomach worms will continue to hatch and develop into larvae capable of infecting stock unless maximum daily temperatures drop to below 8°C for several consecutive days. This June is forecast to be warmer than average — our typical June average maximum is 12°C. That means that worms, in particular brown stomach worm, could continue to cause problems through the next few months. The signs of brown stomach worm include scouring, weight loss or poor weight gain, progressing to collapse and death.

Conducting WEC to gauge if stock, particularly young stock, require drenching before heading into the tougher winter months would be sensible. WormTest kits are available from our Local Land Services office.

Foot problems in sheep have been the theme of this autumn, following a wet, warm and humid period. The conditions have been optimal for the development of foot abscesses, interdigital dermatitis and benign and virulent footrot. Ensuring sheep’s feet have the chance to dry during the day, for example by using well-draining undulating paddocks, is key to avoiding foot problems. Application of zinc sulphate footbathing, particularly in well-conditioned pregnant ewes, may be needed. Autumn lambing and calving are currently in full swing and these producers need to be prudent in listening to weather warnings as cold snaps can be fatal to young stock. In our district, one of the best websites to see current and predicted weather information, including graziers warnings, as well as soil moisture and pasture performance is


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