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Western Australia worms, flies and lice update - December 2014

Albany: Brown Besier, DAFWA (brown.besier@agric.wa.gov.au)

With the steady increase in temperatures and unwanted rains at last dropping off, the main worm control item on the agenda is summer drenching to pre-empt worms in the next year.

Recommendations were given in the November ParaBoss newsletter, but here’s a reminder:

Weaners (red tags) and hoggets (yellow tags)

Drenches given to young sheep in summer set the scene for worm control for the coming winter and spring. A drench should generally be given as a routine to both current year lambs (weaners) and last year’s drop (hoggets).  Drench as the sheep go onto crop stubbles or pastures that have turned dry.

There is usually no point in doing a worm egg count before drenching weaners, as worm egg counts are almost always significant unless they have been deliberately managed by paddock moves to have low worm burdens at this time.

However, in some cases worm burdens may be low in some hogget mobs (especially if from an early drop), and a worm egg count may indicate that no drench is needed. Testing this age group over a couple of years will show whether or not they usually need a summer drench.

Adult sheep

Where feasible, drenches to adult sheep should be delayed until autumn (late March–early April), as this provides a source of less-resistant worms on the farm, to dilute out resistant ones. If it is thought essential to drench adult sheep in summer, a proportion (15–20%) of those in the highest condition scores (over 3.0) should be left undrenched, as another way of providing some less-resistant worms.

Drench effectiveness

Summer drenches should be as close to 100% effective as possible.  Where there is no drench resistance testing history, it is wise to err on the high side and use a drench with actives where resistance is rare (‘triple combinations’, a white, clear and abamectin), or has not yet been found (monepantel, or a derqantel-abamectin combination).

The WormBoss website has more details of summer drenching strategies and drench group options.

Esperance: Nicole Swan, Swan’s Veterinary Services (nicole@swansvet.com)

After the rain we had in November a few cases of barber’s pole have occurred. In one mob of weaners there was an average count of 3495 epg with individual counts up to 22000 epg. It is important that sheep on farms in high risk areas are monitored to determine their barber’s pole status, and detect a potential problem before it is clinically apparent.

The sunny weather continues with the odd warmer (30C) day. Although warm, this weather is not hot enough for long enough to turn pastures into ‘safe’ pastures as far as worms are concerned.

Harvest has pretty well wrapped up for the year. This means that there should be plenty of stubbles available on most properties. Young sheep—weaners & hoggets—should receive an effective summer drench onto stubbles. With the release of Startect (Derquantal plus Abamectin) onto the market, there are now a number of highly effective drench options available. If you are unsure what to use please contact your local vet for advice.

Older sheep should be monitored and any with counts of 200 epg or more should also be drenched.

Wishing everyone a Merry Christmas and a happy and safe New Year.