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New South Wales worms, flies and lice update - July 2020

NSW WormBoss Worm Control Programs

NSW WormBoss Drench Decision Guides






Central West LLS

Coonamble: Jillian Kelly, DV (

Few WormTests have been submitted to the NSW DPI EMAI laboratory. Of those that have been submitted, worm egg counts have risen, with a mix of barber’s pole worm and black scour worm present. The warm weather right up until July meant that barber’s pole worm larvae were still infective and picked up off the pasture well into winter. If this is a sign of things to come and our winters are going to continue to get warmer, it will pose a significant challenge to sheep producers and is worth considering when it comes to drench resistance, pasture management and strategic management of parasite burdens.

We are encouraging producers to do worm egg count reduction trials or DrenchTests on their flocks in spring to assess the extent of anthelmintic resistance on their properties.

Fly activity has abated now that the cold weather has finally started, but producers are reminded to be extra vigilant as spring rolls around. The FlyBoss website has great decision making tools to help decide how to manage fly risk. Producers may have to do an extra crutching or shearing, rather than use multiple applications of chemical prevention to control flies this spring and autumn. 

Cattle in the area are suffering from lice burdens, however, producers are reminded to consider whether they really require a treatment, and if a treatment is necessary to use a product that only targets external parasites to avoid inadvertent internal parasite resistance developing from repeated use.


Murray LLS

Eve Hall, DV (

The Holbrook district has so far had just over 500 mm of rain for the first half of 2020. This is well above the average of 390 mm to July. The excellent autumn break and milder conditions have resulted in good pasture growth. Frosts have generally held off until more recent weeks.

Most problems with stock have been largely associated with green feed (bloat in cattle, and metabolic problems—calcium and or magnesium—in sheep). While there have been limited clinical cases of worms in sheep, local WormTest results from the east of the region have shown some moderate worm burdens.

  • A mob of Merino weaner ewes showing some scour returned an average of 328 epg (50% black scour worm, 50% brown stomach worm). Their last drench was a moxidectin product in February 2020.
  • A mob of Merino ewes in late pregnancy showing some scour returned an average of 300 epg (69% black scour worm, 31% brown stomach worm). Their last drench was an abamectin, levamisole and oxfendazole combination in October 2019.
  • A mob of composite ewe lambs in late pregnancy with no signs returned an average of 100 epg (50% brown stomach worm, 44% black scour worm, 4% small intestinal worm, 2% barber’s pole worm). Their last drench was an abamectin, levamisole an oxfendazole combination in October 2019.
  • A mob of first cross twin bearing ewes in late pregnancy with no signs returned an average of 418 epg (60% barbers pole worm, 22% black scour worm, 18% brown stomach worm). These ewes had previously not required drenching for several years. Subsequently, they received a pre-lambing drench with an abamectin, albendazole, closantel and levamisole combination.

Going forward, producers with spring lambing ewes should be factoring in WormTests prior to pre-lambing drenches, and those with autumn lambs should be considering low-worm risk paddocks for weaning.

Deniliquin: Scott Ison, DV (

Producers in the west of the Murray region have mostly had good rainfall and excellent pasture growth this year. Deniliquin has had 303.2 mm for the year to date, well above the average of 195.9 mm. Cold temperatures and good nutrition would be expected to reduce the risk of internal parasites and clinical worm burdens.

No WEC results have been reported for the area in winter so far.

Sheep producers should consider WormTests before drenching, with weaning imminent for many. 


Western LLS

Bourke: Charlotte Cavanagh, DV (,

With many parts of the region drying off on the flats, stock are congregating in the gullies and water courses where the winter herbage, particularly clover, is remaining fresh. 

We are seeing some scouring stock, and while it may be aggravated by the fresh short feed, the possibility of larval hypersensitivity scouring cannot be dismissed (see Editor’s note, below).

In general, the livestock are in the best condition we have seen for years. The exception is west of Broken Hill, which has unfortunately missed out on the rain.

Editor’s note: Hypersensitivity scouring can occur when sheep are re-introduced onto green feed where there are scour worm larvae, after they have developed immunity to these worms in the previous year/s, or indeed spontaneously on any pasture—there are still many unknowns.

Of particular note is that the number of larvae can be extremely low; frequently not detectable on a WEC or yielding counts less than 100 epg.

These scours do not reflect the sheep gaining a high burden of worms, instead some of the mob will have a large reaction to very few larvae (hypersensitivity) that is out of proportion to the actual number of larvae they have ingested. Think of it like an allergic response. The situation is not well understood, but the scouring response may be an attempt by the animal’s system to purge those incoming larvae. In any one animal the scouring lasts only a matter of days – although it might be apparent across a mob for some weeks due to the different timing of response by each animal. It occurs in adult sheep or young adults that were already exposed to scour worms in previous years because their immune systems are now primed and ready to respond to the next exposure to these worms.

If scouring occurs in younger lambs it is not hypersensitivity, instead it is generally from a large burden of scour worms, and worm egg counts will indicate a drench. Likewise, if individual adults continue to scour (and weight loss may be apparent), then this could be from an ongoing large burden of scour worms. In adults, a worm egg count should be done to check before drenching. If scouring persists, other diseases could be involved, and a veterinary investigation is needed.

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