WRML: Monepantel resistance confirmed in sheep in Australia – two genera, two states

As a result of new information received (2 Dec 2014), this post has been updated.  See https://wormmailinthecloud.wordpress.com/2014/12/05/wrml-20141205-update-monepantel-resistance-on-australian-farms-goats-yes-one-farm-sheep-no/    In short there are no still no reports of confirmed cases of monepantel resistance in sheep on farms in Australia, but read today’s (5 Dec 2014) post for more information.  SL, 2014-12-05

To WormMail mailing list. (recip. undisclosed).

A few months ago, the first confirmed Australian case of monepantel resistance in any species was reported.

That case involved goats on a farm in NSW. Haemonchus was fully susceptible, there was emerging resistance of Trichostrongylus and severe resistance of Teladorsagia to MPL.

More information: https://wormmailinthecloud.wordpress.com/2014/06/27/wrml-update-of-wormmail-on-monepantel-resistance/

Now we have confirmed cases of monepantel resistance in sheep.

With permission, here are excepts from an email (23 October) from Dr Bruce Chick of Veterinary Health Research outlining this development (emphases mine):

Hi Steve​,​

I mentioned a couple of possible monepantel resistant strains to you a few weeks ago. These have now been confirmed via artificial infection, sacrifice and total worm count efficacy studies.

Haemonchus contortus strain isolated from south-western Queensland.

Trichostrongylus colubriformis strain isolated from northern NSW.

We also have strong suspicions of a Teladorsagia circumcincta strain isolated from NSW however this is based on egg count data only at this stage. (See below for update).

Steve, we are undertaking further characterisation work on each of these three strains at the moment ……………


Bruce Chick

Veterinary Director (Sales and Marketing)

Veterinary Health Research Pty Ltd

Trevenna Road (Private Bag)

West Armidale NSW 2350

Australia www.vhr.com.au

​ ”

Update: (SL, 24 November 2014):  It turns out the suspected MPL-resistant Teladorsagia (brown stomach worm) isolate is not from sheep, but is from a goat property. In fact, it is from the goat farm in NSW which was the source of the first reported confirmed* case of MPL resistance in Australia (WormMail, June 11, 2014). More information is being collected on the isolates mentioned in the 28 October 2014 WormMail, so further updates (more detail, property histories etc.) are likely.  (* Confirmed by faecal egg count reduction test (in goats) and slaughter study (in sheep)).

​An aside, for the boffins (differentiating Teladorsagia from Trichostrongylus): I might point out that VHR has the capacity to do PCR as well as traditional parasitology when it comes to differentiating worm species. Some of you will know that when it comes to larval differentiation, there can be problems when using traditional techniques (morphology) to accurately/consistently tell the difference between Trichostrongylus and Teladorsagia larvae. e.g. short-tailed Teladorsagia can look just like Trichostrongylus.

​Practical response to all this?

How do we keep drenches alive for longer and do worm control

Go to WormBoss: www.wormboss.com.au

First digest and start applying information in the ‘Your Program’ applicable to your region. You don’t need to know all or even much of the science to apply these principles. This is good, practical stuff.

The rest of WormBoss provides a wealth of good information to support you.

But first read and apply ‘Your Program’. I don’t think anyone can give you better advice than that.

Secondly, assume nothing. Don’t assume that even newer drenches are 100% effective on your farm. As part of good worm management, periodically follow up a drench with a worm egg count 10 days later (DrenchCheckDay10). Yep, this is covered in ‘Your Program’.