Diagnostic and Analytical Services (agriculture): DrenchTest
Which laboratory?
State Veterinary Diagnostic Laboratory at Menangle (EMAI)
Samples
The DrenchTest kit is available from our customer service units.
Customer service unit
Contact the customer service unit at Menangle.
Feedback
menangle.rvl@industry.nsw.gov.au
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Why test?
More than 90% of farms now harbour worms that are resistant to some drenches. Testing for drench resistance on your property is an important and invaluable management tool and should be carried out at every 2-3 years.
What is 'drench resistance'?
Drench resistance is an increase in the ability of a worm population to survive treatment. This resistance is inherited, therefore the following generation of worms has a higher proportion of resistant individuals. Continued use of the same drench family allows the proportion of resistant worms to increase further. Eventually all worms may survive treatment and drenching will have no effect.
Diagnosing drench resistance
If worm-affected stock have been drenched correctly but fail to improve after drenching, drench resistance may be to blame.
However, failure to respond to drenching may not be due to drench resistance - animals can be affected with something other than worms, for example liver fluke, coccidiosis, malnutrition. Occasionally faulty drenching equipment or incorrect dose rates may be the problem. If stock fail to improve after drenching, veterinary advice should be sought.
Hints for reducing drench resistance
- Know the drench resistance status of your property. DrenchTest every two years. Do a WormTest 10-14 days after drenching as a quick check of effectiveness.
- Drench strategically.
- Rotate between drench families. Know your drenches and rotate them to best suit your situation. Talk to your veterinarian or advisor to help determine the best strategy.
- Never underdose. Use scales to weigh sheep and dose all sheep in mob to heaviest weight.
- Check accuracy of equipment. Measure the dose your drench gun delivers to ensure that it is calibrated correctly.
- Plan clean 'safe' paddocks. Select a paddock in summer to use for lambs at weaning time and do not graze lambing ewes or last year's weaners on this paddock.
- Drench lambs at 14 weeks of age. Preferably wean, drench and move to the selected 'safe' paddock at this time.
- Remember: Drenching selects for resistant worms. Extra drenches should only be given when worms are the cause of scouring or illthrift. Consult your veterinary adviser about this.
- Remember: Good worm control in ewes, good management and nutrition are important factors to help manage worm control.
- Don't import resistant worms onto your property. Use a 'quarantine' drench when buying in sheep and hold the sheep for at least 24 hours after treatment before releasing into the paddock.
The tests available
NSW Department of Primary Industries laboratories offer a sampling kit to test for drench resistance. The DrenchTest kit is available from our Customer service units.
Laboratory charges for Anthelmintic Resistance Packages (Drench Test) will vary depending on the number of drench groups submitted for testing.
Preparing and submitting samples
DrenchTest is used to determine how efficient different anthelmintics are for controlling worms in your sheep. The test can be used on any combination of drenches.
Equipment
- Lambs/weaners – undrenched, bred on property, similar weight (15 animals per group) with an egg count average greater than 200 eggs per gram of faeces. (Important to check egg count with a WormTest before setting up DrenchTest.)
- 1-2 drench guns
- Coloured sheep spray markers (e.g. green, red, blue)
- Quantity of drenches to be tested - enough volume of the different drenches to treat 15 sheep per drench
- 1 measuring cylinder
- Scales
- DrenchTest kit for sample collection - available from our customer service units.
Procedure
Example of setting up one control group and three treatment groups:
- Draft 60 lambs from mob at random, e.g. in mob of 120 lambs, draft out every 2nd lamb.
- Divide the 60 lambs into four groups of 15 at random by drafting four ways.
- Using scales, weigh a few of the largest sheep. Ensure that you treat all sheep at the dose calculated for the heaviest in that test group.
- Check gun delivery. Squirt 10 doses into a measuring cylinder, divide the total volume by 10 to give the output of the gun. Adjust the gun, according to the manufacturer's instructions, and repeat the procedure until the gun delivers the correct dose. Preferably use different guns and packs for each drench group. If using only one, wash the gun and pack thoroughly, and recheck the gun delivery when changing drenches.
- Mark heads of the first group of 15 lambs with a coloured mark (e.g. green) – DO NOT drench this group - this is the Control group. Record the colour on the sample submission form provided.
- Mark the heads of the second group with another colour mark (e.g. red). Drench with the chosen drench and record the colour and drench used on the sample submission form.
- Repeat this process for all the drench groups to be tested.
- Box all 60 lambs together and return them to mob.
Sample collection
Ten to 14 days after drenching, collect the sample as follows.
- Muster the mob in the early morning and draft marked lambs into colour groups. Minimise the lambs' stress as it is difficult to collect adequate samples from stressed lambs.
- Collect 10 individual dung samples from 10 of the lambs in each group (a minimum of 10-15 pellets per lamb) and place in the vials provided. Samples should be collected from the rectum of each sheep. Place the 10 full sample vials into the large plastic cylinder provided and label with the colour and drench used for that group. Repeat for each group to be tested.
- Fill out the sample submission form and send the samples to the laboratory via a courier.
Which laboratory conducts the tests?
The State Veterinary Diagnostic Laboratory located at Elizabeth Macarthur Agricultural Institute (Menangle).
Customer service units
Contact the customer service unit at Menangle.
Feedback
Your feedback is always welcome. Our laboratory operates to ISO 17025 standard, and we will respond to all comments or criticisms of our service.