Despite the levels of resistance to the most commonly used doses, farmers should not despair since the standard drenches will still work in some flocks.
Step 1 Plan ahead
Doing a drench test will take up to three weeks to get results back, so make sure you are planning far enough in advance before treating the whole flock.
You also need to get in touch with the lab before you take any samples - they'll send you the proper containers to do the job - postmen are not too keen on dealing with bags of faeces in the post!
There are seven approved labs listed on the Department of Agriculture website charging anything from €7-30 to do the test - a small price to get on top of this problem.
Step 2 Sample pen
When you have the kit, put about 15 lambs in a clean pen for approximately one hour. It must be clean so that you're not contaminating the samples.
You're aiming for samples from about 10 different animals in order to see what's happening throughout the flock, so if you have 15 you're covered in case some don't pass any faeces.
Use gloves and separate containers for each animal. These will then be pooled in the laboratory. The samples need to go in the post straight away. If they need to be held overnight, keep them refrigerated to prevent the eggs hatching.
Step 3 Treat and mark
Treat the animals with whatever dose you were planning to use on the flock. Don't forget to mark the lambs because you need to sample the same ones after the treatment.
Step 4 Mark Again
Gather up the same group of lambs in another clean pen and repeat the sampling procedure.
Remember that you need to wait seven days before re-sampling a yellow dosed group, and 14 days for animals treated with white or clear doses.
Step 5 Act on Results
It will take up to a week for a result to come through.
If less than 95pc of the worms have been eliminated from the sample, you need to switch to a different treatment.
If this is the case, you have the choice of repeating the process using a different type of product on a new group of lambs.
Another option is moving to a more thorough (but more expensive) individual faecal egg count test for animals within the flock.
You will need the help of your local Teagasc advisor or vet to complete this.
Just because parasites in your flock are resistant to a white dose, for example, does not mean that a yellow or clear dose will not work either.
However, if the worm population proves resistant to all three of these products, there are other newer 'dual-active' products that have yet to experience any levels of resistance.
The downside of these of course, is that they are up to three times more expensive per animal.