Testing is key for fighting drench resistance

Ensure your drench is effective

Drench resistance is a serious concern for sheep farmers. Regularly using ineffective drenches will just make drench resistance worse at a rapid rate. The only way to ensure that the drench you are using is effective is with regular faecal egg count (FEC) testing – you can’t accurately diagnose drench resistance by eye.

Check, don’t guess

Regular drench checks are the simplest way to find out where you are at. Working together, Farmlands and FECPAK are making this much easier. FECPAK has developed an Animal Health Multi Test Kit. It is available from Farmlands stores and includes everything to take a sample from the field and courier it to the lab for testing. Paying per test, the FECPAK Animal Health Multi Test Kit allows farmers to choose up to four tests – including FEC and Worm ID – from the one sample. Samples should be taken between seven and 14 days after drenching.

Test across seasons

Previously, full tests of multiple actives were undertaken to assess the resistance status of a farm. Called Faecal Egg Count Reduction Tests (FECRTs), this type of test is relatively complex and only undertaken every few years. By comparison, regular pre- and post-drench checks allow farmers to look at the resistance status at different times of the year. This is important as different species of worm have different resistance statuses and are present at different times of the year. A single FECRT may not capture them all. Farmers should complete a routine drench check for lambs around weaning, mid-summer and in the late autumn or early winter as a minimum.

Reading the results

If no eggs are present post-drenching that is a green light – the drench appears to be working. If there are eggs present in the faecal sample, that is a red light and further investigation is needed.

Check the drenching process

First, review how the drench was administered:

• Were the sheep weighed correctly - if at all?
• Was the drench gun accuracy checked?
• Were all the animals drenched?
• Were any refugia animals included in the mob and not drenched?

Once these variables have been checked, repeat the FEC testing.

Repeat the test

Take both pre- and post-drench samples and sample animals individually. Ideally, use another mob of sheep on the property that has not been drenched recently. When drenching these animals, drench to individual bodyweight to ensure they are given the correct amount of drench. Post-treatment FEC samples are taken again seven to 14 days later.

Identify the worm species

From a single faecal sample a farmer can choose up to four tests, including a FEC test and also the new Worm ID test, which identifies the worm genus present. When undertaking more detailed FEC testing, farmers can also include other drench combinations. If the current drench has a problem, consider testing the product you plan to use next. A problem with a drench at one time of the year does not necessarily rule out its use at another time, when the resistant parasite may not be present.

Look beyond drench

Drenches are only one part of a farm’s parasite-management plan. Cross-grazing different stock classes and species alongside the use of crops, high-quality forages and supplements, can help reduce production losses from parasites. Refugia should also be part of the plan. Refugia refers to the portion of the parasite population that is not exposed to drench. Maintaining a population of drench-susceptible parasites helps dilute resistant survivors and slow the development of resistance. Although this whole-farm approach to parasite management can appear confusing, the first step is simple: conduct a drench check using a FECPAK Animal Health Multi Test Kit. It is also the most important step because it tells you whether you’ve got a drench-resistance problem on your farm or not.

Reference: Miller, CM, TS Waghorn, DM Leathwick, PM Candy, AM Oliver and TG Watson (2011), “The production cost of anthelmintic resistance in lambs”, Veterinary Parasitology.