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Quarantine drench – Avoid bringing resistant worms on to your farm

At this time of year a lot of sheep move between farms, whether its rams, breeding females or store lambs. Any new sheep entering flocks pose a potential biosecurity risk, in particular the risk of bringing resistant worms with them. Ciaran Lynch & Dr Orla Keane Teagasc discuss the quarantine drench

New sheep entering flocks is one of the major ways anthelmintic resistance has spread from farm to farm. Therefore it is important there is a proper quarantine procedure to deal with incoming sheep to clear out any worm burden they may be carrying. In order to prevent the importation of resistant worms there is a need to quarantine dose these sheep. This is one of the few times where it is recommended to dose adult sheep.

Quarantine Drench

Sheep should be treated upon arrival onto the farm. One of the two new anthelmintic groups should be used as part of the quarantine treatment. These are either Group 4-AD (Monepantel) sold under the trade name of Zolvix or Group 5-SI (Spiroindoles) sold under the trade name of Startect (although this is currently unavailable in the Irish market). Both of these anthelmintics are already prescription only medicines (POM) so you will need to contact your veterinary practitioner to order these. In order to protect these two new classes of anthelmintic it is advisable to use them with one of the existing wormers that works on your farm, possible quarantine strategies are as follows:


Option A: Dose with 4-AD (Zolvix) + a second wormer, the second wormer can be from either the 3-ML (clear) group or alternatively the 2-LV (yellow) group. These 2 doses need to be given sequentially and the products cannot be mixed.


Option B: Dose with 5-SI (Startect - when available) + a product from Group 2-LV (yellow group). As Startect is a dual active product that contains abamectin (Group 3-ML) it is recommended it is used in combination with a Group 2- LV levamisole. Again these 2 doses need to be given sequentially and not mixed.

Each time you’re treating with an anthelmintic, it is important to check the dosing equipment is consistently delivering the correct dose and ensure the dose delivered is given at the correct amount for the animal’s body weight and according to the manufacturer’s instructions. Care needs to be taken particularly in the case of adult sheep, where the weight range may be large.

Post dosing

After treatment the sheep  should be housed for a minimum of 24 hours and ideally 48 hours to prevent any resistant worms that may be in the digestive tract passing out on to your pasture. This will also give an opportunity to identify other issues e.g. lameness. Following the housing period the sheep should be turned out onto dirty pasture (i.e. ground under continual/regular sheep grazing) to pick up the worm population on your own farm.

Some planning is needed before new animals arrive on the farm, first and foremost to have suitable anthelmintic to hand. As some of the recommended products are already POM, contact with your Veterinary Practitioner is necessary, additionally other products may not always be available from your local provider. Have suitable for housing arrangements for these animals and a source of forage/feed on hand. 

Control of internal parasites is a challenge, long term it is important you don’t make the situation worse on your own farm by buying resistance problems in – Quarantine treat them!

To find out more watch as Dr Orla Keane explains the quarantine dosing process for bought-in sheep in this video clip

The Teagasc Sheep Specialists issue an article on a topic of interest to sheep farmers every second Tuesday and from time to time here on Teagasc Daily.  Find more on Teagasc Sheep here