ParaBoss News - January 2021 - Feature Articles

Australia's resource for control of worms, flies and lice in sheep,
and worms in goats

Parasites in the farm’s dam

Yabbies are common in farm dams and are susceptible to various parasites, such as Epistylis and Temnocephala. Epistylis appears as a fluffy growth on the external surface of crustaceans and fish. It is considered relatively harmless, as it simply uses the host animal as a platform from which to feed on bacteria and particles in the water. However, when present in large numbers it can asphyxiate the animal by restricting water flow over the gills. Temnocephala are flat worms that lay their eggs in the gills and on the shell of crustaceans. The worms feed on algae and microfauna on the surface of the crustaceans and do not pose a huge health risk to the animals. The presence or either of these parasites is an indicator of low oxygen levels and poor water quality of the dam.

Temnocephala eggs on the underside of a yabbie
Image: DPIRD

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A handy quick-reference for on-farm advisors

Are you working with producers to help them manage worms in their flocks? The WormBoss Programs and associated Drench Decision Guides are here to help you guide producers in developing and implementing a worm management strategy.

The WormBoss Programs outline the control strategies and the practices and timing of these throughout the year.

The Drench Decision Guides (DDGs) can be used as a quick reference on whether a producer needs to drench now, drench later, or conduct a WormTest to gather more information.

A key feature of each of the regional-specific DDGs is the worm egg count thresholds, which set out the number of worm eggs per gram of faeces at which different classes of sheep are recommended to be drenched. The thresholds represent a level where the value from lost production or deaths is consistently outweighing the cost of treatment. These points are always before signs show.

You can use these thresholds to indicate to your clients the point at which ongoing worm issues will be costing them more money than if they treated at that time; when signs shows production loss is already significant.

Find out more about the WormBoss Programs and Drench Decision Guides

The Drench Decision Guides are available as a digital questionnaire or a hard-copy document (pictured above)

Hand-jetting using a Dutjet wand.
Image: Peter James

Rotate your flystrike treatments to avoid resistance

Flystrike has been a big problem on farms this summer, driven by warm and wet conditions across much of the country. For those who haven’t experienced a high flystrike season in recent years, or whose breeding for flystrike resistance program is still a work in progress, the shift in risk profiles has caused a need to re-evaluate their prevention and treatment methods.

There are a number of chemical treatment options available for flystrike, however, just like with worm control, flies and maggots can become resistant to chemical treatments over time. It’s important that you rotate your chemical actives to slow the development of resistance, especially if you find yourself needing to treat twice in a season to deal with ongoing strikes.

As with all on-farm chemicals, it’s important to get the right advice. Speak with your veterinarian or reseller to ensure you’re choosing a product which will meet your needs, or consult the FlyBoss tools.

Find out more about selecting the right flystrike treatment.

Commercial flystrike-chemical resistance testing now available

If you think your flystrike preventative chemical is not working for as long as it should, or you simply want to establish a benchmark for your property, you can have maggots from your property tested to see if they are resistant to chemicals.

You can send a large sample of Lucilia cuprina maggots from a struck sheep to the NSW DPI EMAI laboratory and they can test for four chemical groups (five chemical actives).

Find out more about the commercial tests.

Treating introduced sheep to prevent lice

Have you managed to eradicate lice previously, but had them pop back up at a later date? If you’ve looked at your management strategy and can confidently say that you didn’t miss any on your property, you might be left wondering where those lice have come from.

Depending on where you source your sheep, it’s possible you’ve inadvertently brought lice in on some introduced sheep. The prevalence of lice varies between flocks across the country, but broadly speaking, at least 20 or 30% of flocks will have lice, so it’s safest to assume that every new sheep (and ram) on the property poses a lice risk.

There are a number of options for managing lice risks, including quarantine, and shearing and chemical treatments. Regardless of how you proceed, the best bet is to apply some form of control measure to prevent reintroducing lice to your flock. The LiceBoss Treatment Decision Guide can assist in choosing which approach is the best fit for your current circumstances.

Find out more about stock introduction for lice control.

Shearing and treating new arrivals is the best option for biosecurity, but must be weighed against the costs.

Testing your herd helps make informed drenching decisions.
Photo: Berwyn Squire

Don’t act without all the information!

For goat producers, good drenching practice is all about making informed decisions. While the WormBoss tools can provide guidelines, they are not tailored to the specific conditions on your property, and even within a region, worm burdens and drench resistance will vary between farms. For this reason, it’s important to have as much information as possible to inform your approach.

A WormTest is the easiest way to know whether or not to drench your herd, by indicating the number of worm eggs found in goat faeces. A DrenchCheck (the use of a WormTest on either side of the drench) can help assess the effectiveness of the drenches you are using, by measuring the extent to which the drench is reducing worm numbers.

For the larger scale goat producers, a more comprehensive DrenchTest is recommended every few years, to help assess not only the effectiveness of the drenches used on the property against the worms, but also against one another, to ensure you’re using the most effective drench active.

Find out more about testing your herd to help make worm control decisions