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New South Wales worms, flies and lice update - April 2015

Armidale: Rad Nielsen, Veterinary Health Research (rnielsen@vhr.com.au)

Worm pressure continues to remain high in the New England region for a portion of sheep producers. Some extremely high worm egg counts (WECs) have been identified in the VHR Laboratory over April, predominantly Haemonchus dominant infections. Rain over Easter and again more recently will have stimulated further worm egg hatching and larval development on pasture. Continued close monitoring and observation is advised for those graziers who have been having worm issues this summer/autumn.

The Haemonchus threat has also been experienced in more southern regions. Some exceptionally high WECs have been seen in sheep from the upper Hunter and Coolah districts, in particular. A number of properties in the Gunning district have also been identified as having relatively high Haemonchus burdens in some mobs of sheep.

A reminder regarding liver fluke—April/May is a key time to treat for this parasite in both sheep and cattle. Faecal and/or blood tests can be used to confirm stock are harbouring fluke infections. Of great concern has been the identification in recent years of a number of New England properties with genuine triclabendazole resistance within the resident liver fluke population. Graziers and their advisers need to be aware of this potential issue, particularly in instances where stock fail to respond to fluke treatment. Ideally, a pro-active stance should be taken and at least post-treatment (3–4 weeks) worm egg counts conducted to ascertain fluke status.

 

Armidale: Stephen Love, Veterinarian, Parasitologist, NSW Department of Primary Industries (stephen.love@dpi.nsw.gov.au)

Case study—a good reason to WormTest and DrenchCheck

Dr Jim Kerr, Wingham-based District Veterinarian for the Hunter Local Land Services, told me of deaths he investigated in 6–8 month old Dorper lambs in the Gloucester area of NSW.

Five out of 13 lambs died in February. They had been drenched with Q-Drench® (abamectin + albendazole + levamisole + closantel) in February, then again on 15 March. Two more died after the mid-March drench and another two were pale. They were mostly set-stocked, i.e. mostly grazed the same paddock.

Faeces from 8 lambs were submitted to the lab on 7 April, approximately 3 weeks after the last Q-Drench. The average strongyle egg count was 17,760 eggs per gram of faeces (epg), with individual counts ranging from 80 to 70,000 epg.

The pre-patent period for Haemonchus can be as short as 18 days, and these samples were collected about 23 days post-drench, but I think it can be safely assumed (drench maladministration etc. aside) that Haemonchus on this property is resistant to Q-Drench and each of its constituents.

With these results, a decision was made to use one of the newest drench actives, Monepantel (Zolvix®), for the most recent drench, since the four older actives were apparently not working. A follow up DrenchCheck done on day 11 after drenching yielded all zero egg counts.

All this of course could have been simply avoided through regular WormTests and periodically checking drench efficacy with a WormTest after drenching (DrenchCheckDay10). Although called Homo sapiens (‘wise man’), we humans are not always super-smart.

Consider this graph below, a partial summary of a survey of drench resistance in Australia published by Playford and others in December 2014.

 


Figure. Percentage of tested sheep farms with drench resistance (Australia, 2009–2012)

Notes: BZ=benzimidazole, ‘white’. LEV=levamisole, ‘clear.’ MPL=monepantel (‘Zolvix’, an ‘AAD’. No resistance detected).The macrocyclic lactone (ML, ‘mectin’) drenches are: IVM=ivermectin, ABA=abamectin, MOX=moxidectin. BZ/LEV etc. are combination drenches. CLOS=closantel. *Less than 50 usable drench tests for this drench. ‘Resistance’ here means the worm egg count reduction after treatment was <95% for one or more of Haemonchus, Trichostrongylus or Teladorsagia species. Reference: Playford MC, Smith AN, Love S, Besier RB, Kluver P and Bailey JN. Prevalence and severity of anthelmintic resistance in ovine gastrointestinal nematodes in Australia (2009-2012).Aust Vet J 2014; 92: 64-71.

To explain, take the BZ bar, which is up level with about 95. That means 95% of properties tested had some level of resistance to BZ drenches.

Consider the graph and the case study: good reason to do regular WormTesting and DrenchChecks, don’t you think?

 

LOCAL LAND SERVICES DISTRICT REPORTS

Riverina LLS

Young: Rahul Shankar, DV (rahul.shankar@lls.nsw.gov.au) and Eliz Braddon, DV (eliz.braddon@lls.nsw.gov.au)

Rainfall varied between 53mm and 77mm in the 2–3 days of rain from last week. A welcome reprieve! 

WormTests have been steadily coming through after the rains we experienced in Young and its surrounds last week. 

Counts have varied from 40 epg–5,800 epg in counts received thus far. Unfortunately, larval differentiation was not performed in the samples that were tested to date, so exact species were unable to be identified. One producer was experiencing issues in his 8–10 month old lambs, which was strongly suggestive of a barber’s pole worm burden. He has lost 6 out of a mob of 800, with traditional signs of a bottle jaw, anaemia and a tail to the mob being present. 

With more rains coming, producers have been told to be mindful of worms in their pastures and to undertake additional WormTests 4–6 weeks after these rain events to ensure that their counts are kept in check.

 

South East LL

Cooma: Petrea Wait, DV (petrea.wait@lls.nsw.gov.au)

Here on the Monaro we are still seeing significant losses as a result of barber’s pole worms. One producer reports losing over 100 ewes, and we have seen counts as high as 41,000 eggs per gram.

This is the result of the long mild and wet period we have experienced from spring through to autumn, which doesn't look to be ending any time soon with continuing good rainfall. Once we get some more wintery weather we should see a reduction in the barber’s pole numbers, as eggs can’t develop to larvae once daily maximum temperatures drop below 18 C, though scour worms are much more cold tolerant. However, even with cold and frosts stopping new development, the larvae that hatched earlier will still be there to infect sheep through winter.

Liver fluke have also been causing problems for producers this year. One property had almost all of their weaner lambs affected, with poor growth rates, anaemia and weakness. Blood tests performed on these lambs showed very high levels of liver fluke, but faecal egg counts only showed a few fluke eggs. Blood tests are far more sensitive to detect liver fluke in livestock as they can detect fluke larvae, which don't lay any eggs but do cause all the damage to the liver.