In this issue:
- WormFaxNSW-March 2016
- Drench resistant cattle worms – Wonders
- WECs don’t tell the full story in dairy cattle either – Wonders
- Monepantel matters
- Cooper Curtice
- Profarm courses
- Kelpies and dingoes, antibiotic resistance, pediatric myopia, first illegal immigrants etc
The March edition, along with explanatory notes, is now up on the DPI website:
Now, let’s see who scored the highest worm egg counts (WECs):
- Armidale had the highest ( mean WEC of 13 380 epg (range 5440 – 18640, 100% Haemonchus), narrowly eclipsing …
- Central Tablelands (mean WEC 11 660 epg ( range 7920 – 15 400, 93% Haemonchus)
Drench-resistant cattle worms in Australia – Dr Nick Wonders
Merial vet Dr Nick Wonders did a presentation on this subject at a recent (April 2016) Australian Cattle Veterinarians meeting at Ayres Rock, NT. He presented data from a Merial sponsored survey. The abstract is in the public domain. Here is a link to it: Wonders-N. 2016.Abstract – What does anthelmintic resistance mean for worm treatment in cattle. Aust Cattle Vets, Ayres Rock Autumn 2016
Why am I posting it here? Well, I think it is important information, an acceptable/standard protocol was used, the field work was done by a variety of people, not just company employed or sponsored persons, all the actives tested were affected (i.e. less than 95% efficacy) to some extent, including actives Merial markets. (Of the actives for which there are results, Merial markets all of them in Australia in ruminants except doramectin, and, in cattle, all of them except doramectin and oral benzimidazole (BZ) drenches).
The study was done on 36 Australian farms, mostly in NSW and Victoria. The farms were not randomly selected. It is not claimed that reliable estimates of prevalence of resistance were obtained for a particular region or regions. The prevalences reported here are clearly proportions of farms tested that yielded particular results. You could say these results are indicative of what the prevalence of resistance in the field might be.
Rather than getting mired in the detail, perhaps the most important take home point is that 75% of the farms tested had resistance (efficacy <95%) to at least one of the single active macrocyclic lactone drenches tested. [This was in at least one worm species based on larval differentiation (Ostertagia, Trichostrongylus, Haemonchus and Cooperia spp). Based on undifferentiated strongylid egg counts, it was closer to 66%].
And of course resistance to the other drench groups was common as well.
If you prefer pictures, here is a PowerPoint slide that I put together and sometimes use. It is based on the Merial dataset. The usual caveats apply regarding over-interpreting results, particularly with very small numbers of farms/tests. So, for example, the results do not say resistance to moxidectin LA injectable occurs on 100% of farms!
Take home messages:
- Resistance to cattle drenches is common.
- Combinations have benefits. Everything else being equal, they are more likely to kill more worms including resistant worms.
- These results are not a guide to what an individual farm should use. Testing on each farm is required. This can be as simple as frequent DrenchChecks (WEC on, or just before, the day of drenching a mob, and then again 14 days (in cattle) after drenching, with preferably a larval culture (‘worm type’) being done as well).
WECs don’t tell the full story in dairy cattle either
We know WECs (unfortunately) don’t tell the full story in cattle regarding actual worm burdens and the impact of these burdens on productivity. In a previous WormMail, there is this:
“…. NSW and Victorian trials (see below) (found) that worm egg counts have limitations in cattle, particularly when it comes to predicting likely production losses from roundworms”.
“So, consider on-going evaluation of your worm control program, what drenches you use, and whether you have drench resistance. Objectively assessing these might have a big impact on cost of production and/or productivity, and therefore the bottom line.
URLs for reports on Central Tablelands (NSW) and Victorian (MLA-supported) ‘producer demonstration site’ (PDS) trials:
Eppleston J and Watt B: http://tinyurl.com/jqwu3w7 Rolls N and Webb Ware J: http://tinyurl.com/zhavhdb ”
I can’t guarantee the above links will work – or won’t be changed -so here is a PPT slide that provides a summary:
While at Ayres Rock, Nick Wonders also presented some data on the effect of drenching dairy cattle at calving. He was reporting some work done roughly 15 years ago. Here is the abstract: Little G et al 2000 Effect_of_Eprinomectin_at_calving_on_milk_production Socy Dairy Cattle Vets NZVA-frm Nick W 16 04 20
- Australian study on 2,599 dairy cows on 9 farms
- Drenched at calving (eprinomectin). (The merits of different drenches is not the main point here).
- Average effect, compared to untreated controls, on milk production per treated cow over 100 days:
- milk volume up by 1.8% (2642 vs 2595 L)
- milk fat up by 1.8% (101.0 vs 99.2kg)
- milk protein up by 2.6% (87.1 vs 84.9)
- On ~18% of the cows, nematode worm egg counts (WECs) were done, with the detection limit being 2 eggs per gram. (Typically the detection limit for cattle WECs using the usual lab method is 20-25 epg).
- before treatment, ~47% of untreated controls and 41% of cows to be treated had positive strongylid WECs
- only 2.4% had WECs >40 epg.
The main point I take from this is that high WECs in cattle may mean something, but low WECs, certainly in adults, may not, i.e. there can still be significant production losses with low WECs. So, for cattle in particular, measuring production as well as WECs is necessary to see if there are significant adverse effects from worms.
And something else that needs to be regularly measured: drench efficacy. Resistance is common. How much is lost through the unwitting use of less than highly effective drenches?
Following are two recent papers -and an excerpt from one – on resistance to monepantel. As always, you need to read the papers for yourself!
A. Raza et al. Larval development assays reveal the presence of sub-populations showing high- and low-level resistance in a monepantel (Zolvix®)-resistant isolate of Haemonchus contortus. Veterinary Parasitology 220 (2016) 77–82. http://www.ncbi.nlm.nih.gov/pubmed/26995725
An excerpt: ‘This study demonstrates that a larval development assay is able to detect resistance to monepantel in H. contortus, and that resistance can exist in two distinct forms. This suggests that at least two separate monepantel resistance mechanisms are acting within the worm isolate studied here, with one or more mechanisms conferring a much higher level of resistance than the other(s)’.
D.J. Bartley et al. Phenotypic assessment of the ovicidal activity of monepantel andmonepantel sulfone on gastro-intestinal nematode eggs. Veterinary Parasitology 220 (2016) 87–92. http://www.ncbi.nlm.nih.gov/pubmed/26995727
Cooper Curtice – what’s in a name?
Dr Keith Dash (of WormKill, and other, fame) has told me about Cooper Curtice’s 1890 book “The Animal Parasites of Sheep”, which contains the the original description of Oesphagostomum columbianum. (Keith did his PhD on this worm).
So, what else? I guess you have heard of the small intestinal worm, Cooperia curticei ? and the genus, Cooperia ?
Profarm course list
- Antibiotic resistance -and phage therapy etc.http://www.abc.net.au/catalyst/stories/4446258.htm
- Increased prevalence of myopia in children? – and a simple preventative measure
Kelpie interacts with sheep – a great pic (by Carey Edwards)
Kelpies – a dash of dingo?
‘The Australian kelpie is considered the best all-round stock dog on Earth with its abilities taking it from Australia’s dusty Outback to even herding reindeer in the Arctic. But the kelpie’s origins are shrouded in mystery.’
‘The kelpie takes its name from a water spirit of Scottish folklore’.
Dingo genes dominant over domestic dogs
University of Sydney excels in latest QS rankings
“Veterinary Science (at Uni Syd) was ranked ninth in the world and number one in Australia.”
(This is mainly to annoy my veterinary friends/colleagues who studied ‘elsewhere’.)
The first illegal immigrants?
Map of Britain before the first illegal immigrants. A bit after actually; they had started to colonize the east coast. There would be similar maps for other regions, e.g. NZ, Australia (~ C.18), the americas, Africa etc