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ParaBoss News - May 2021 - Feature Articles

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Fast Fact

H. salminicola spores. Image: Stephen Douglas Atkinson
H. salminicola spores. Image: Stephen Douglas Atkinson


The tiny parasite which doesn’t breathe

Henneguya salminicola (also known as Henneguya zschokkei, which is even harder to say!) is a microscopic parasite which forms small cysts in the flesh of several species of salmon. The parasite appears to have no ill effect on the fish themselves and is harmless to people and pets if ingested. The cysts break down and release countless microscopic spores into the water during decomposition of the host, which go on to infect an intermediate host, likely a type of aquatic worm, before returning through ingestion of the intermediate host by juvenile salmon.

A distant relative of jellyfish and corals, H. salminicola became notable in early 2020 as researchers sequencing its genome discovered that it was lacking a mitochondrial genome, which includes the portion of animal DNA that is responsible for respiration. This means that not only does H. salminicola not need to breathe, it is also the only known multicellular animal that is biologically incapable of turning oxygen into energy to power its cells. While researchers are uncertain as to how this parasite survives without converting oxygen to fuel, it’s been suggested that it is capable of harvesting the necessary energy from its hosts.

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Wormcasts are podcasts produced by ParaBoss covering parasite management topics — worms, flies, lice, ticks and fluke — for sheep, cattle and goats.

Listen through a podcast app, such as Google Podcasts, or Spotify, or on the website.

Feature Articles

Finding the most effective drench for your property

Drench resistance is a huge problem for the industry, as it limits the number of effective drenches which producers can use in their flocks. 

Drench resistance is a self-perpetuating problem because resistant worms that survive go on to breed and multiply. With each drench thereafter, more and more worms survive (and continue to multiply).

Knowing how effective your drenches are doesn’t need to be a big mystery. Conducting a DrenchCheck by completing a WormTest both before and 14 days after drenching will allow you to see the extent to which that drench has wiped out the worm population in the sheep’s gut. In ideal circumstances, you would use a drench that reduces the egg worm count by at least 98%.

You can also conduct a DrenchTest by following a similar procedure, but with groups of 10-15 sheep per active ingredient you want to test instead of the whole mob. By comparing these results, you can find out which are the most effective actives. As worms are less likely to be resistant to multiple actives all at once, you can use your two to four most effective ones in a combination for maximum effect.

Find out more about testing to help select drenches via

Planning your shearing and crutching for maximum protection

Shearing and crutching are crucial dates on the calendar, and it’s extremely important to plan the shearing time to fit with your lambing time. However, the perfect time to shear before lambing might not be completely ideal for flystrike management. Both shearing and crutching provide up to six weeks flystrike protection. Hence, depending on the timing, the protection can last through peaks of high-risk fly activity.

As the seasonal prevalence of blowfly and lambing management differs from farm to farm, there is no blanket rule on planning shearing and crutching times. The good news is that FlyBoss has developed the Flystrike Risk Simulator and the FlyBoss Quick Tools to help you work out when the flystrike risk is highest at your farm, based on local climate data, and help optimise your shearing and crutching calendar for maximum protection. The FlyBoss Tools also allow you to compare different strategies and timings and evaluate how these change the risk. One useful note to assist you in designing the calendar is to utilise the weakness of flies: cold! As flies do not like the cold weather, longer wool during winter will result in relatively lower risk than in other seasons.

With good flystrike management, you will not only see welfare benefits but also economic benefits, as the wool quality is preserved without the impact of flies and maggots.

Find out more and access the FlyBoss Tools at

To treat or not to treat? That is the question, and here is the answer!

Chemical treatment for sheep lice (Bovicola ovis) is commonly applied after shearing when a lice infestation has been identified ahead of shearing. The big question is, is it safe to not treat if no lice were found and no sheep were seen rubbing? To answer this question, we need to figure out the risk of low-level lice infestation in the flock when no lice were found during inspection.

A flock might seem free from lice but there is always the chance a small infestation is still present, especially when there is:

  • a limited number of sheep inspected for lice
  • no quarantine of any stock introduced in the past six months
  • no farm biosecurity plan or stock-proof fences, leading to a high chance of strays.

If any of the above applies, it may be worth treating for lice, especially if there is a high concentration of lice-infested flocks in the region. A small infestation can turn into a big problem if left untreated!

To aid in the decision to treat, the flock needs to be inspected for lice a few weeks prior to shearing, covering the 20 most rubbed-looking sheep. With strong biosecurity and quarantine measures, the risk can eventually be reduced to a level that warrants no treatment when no lice are found. However, it can be wise to treat for another two years from the last confirmed infestation. Once you’re confident you’ve eradicated lice entirely, you can stop chemical treatment. Keep in mind that all the other measures will still need to be in place to prevent reinfestation!

Find out more and access the LiceBoss Tools to aid in decision-making at

Managing grazing and browsing for goat worm control

Goats aren’t known to be picky eaters – which is why they might end up eating worm larvae! The life cycle of many commonly found worms from eggs to larvae and finally adult worms involves a number of growth stages not only inside of the animal but also on pasture. Thus, when discussing worm control, grazing management is just as important as, if not more important, than drenches.

We can stop the exposure of goats to worms by preparing low worm-risk paddocks for them to graze on. This involves a number of strategies, chief among them being the resting of paddocks to break the worms’ life cycle, leading to the death of larvae on the pasture. Rotational grazing can be a good approach to facilitate worm control as paddocks take turns to rest. Alternatively, paddocks can be used for either cropping or grazing by cattle or horses. You can also reduce exposure to worm larvae on pasture by providing goats with suitable vegetation to browse, as opposed to grazing.

Grazing management is beneficial as it decreases the reliance on drenches and slows the build-up of drench resistance. The key to successful grazing management is to plan early and design the management plan that suits your farm best.

Find out more about grazing management for goats via

Dr Jessica Morgan, DAF, at the launch of ParaBoss for cattle, Beef Australia 2021.
Dr Jessica Morgan, DAF, at the launch of ParaBoss for cattle, Beef Australia 2021.

New world-class ParaBoss for cattle launched

Cattle producers now have the same world-class parasite management information at their fingertips that sheep and goat producers have benefited from for years after ParaBoss for cattle was launched at Beef Australia 2021 in Rockhampton in early May.

There are now WormBoss, FlyBoss and LiceBoss websites for cattle, as well as TickBoss.

ParaBoss Executive Officer, Dr Deborah Maxwell, University of New England, said, “This world-leading resource is independent, practical, proven, and profit-enhancing and will help Australian cattle producers to maintain high standards of animal welfare and product integrity.”

Dr Maxwell said, “This was a massive undertaking by the project leader, Dr Jessica Morgan, from Queensland Department of Agriculture and Fisheries, as well as a technical committee, topic leaders, other topic experts, our web developer and web administrator, and of course the funding from Australia’s cattle producers and Meat and Livestock Australia.”

All the sites for both cattle and sheep can be found from

ParaBoss for cattle was created by the leaders in the field of cattle parasitology:

Topic leaders

  • FlyBoss – Geoff Brown (DAF – Animal Science)
  • LiceBoss – Peter James (UQ-QAAFI)
  • WormBoss – Jenny Cotter (DAFWA, now private consultant)
  • TickBoss – Cath Covacin (DAF – Biosecurity)

Technical advisory committee 

  • Jess Morgan, Peter James, Deb Maxwell, Felicity McIntosh, Geoff Brown, Johann Schröder, Cath Covacin, Matt Playford, Jenny Cotter, Lewis Kahn

Web development, web administration, and products tool development

  • Graeme Wright (Wrightway Design), Jody Burgess, Deb Maxwell

Special thanks to 

  • Lex Turner, Brown Besier
  • Numerous writers, editors, reviewers and support staff (see who they are here).

*Thanks to Darren Ho for his assistance in drafting some of this month's newsletter articles. 


ParaBoss News is produced with support
from Animal Health Australia

For May 2021 state outlooks, please follow the links below:
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