Health Care

Score5 (3 Votes)

Quarantine drenching - you only get one shot

Written by Dr Tim Elliott

Dr Tim Elliott is a large animal scientist with over 15 years’ experience. Tim has a particular interest in production animal parasitology and drug resistance. Tim’s work has been published in internationally renowned journals and has presented his work around Australia for scientific audiences and farmer groups.

Every time we drench, we select for resistant worms as the worms that survive the drench pass on the resistant genes to their offspring. If we use the same drench continuously, drench too often or under dose the animals, the number of resistant worms in the population will increase. Worm management programs are vital to prevent this from happening.

One of the quickest ways to get drench resistant worms onto your farm is with a truck! Any sheep arriving onto your farm that were not born and grazed on your farm can carry parasites that may be resistant to drenches and can be the downfall of your parasite control programme. When sheep arrive on your property, the assumption must be made that these sheep are carrying parasites that may be resistant to a variety of drenches, and must be treated as such.

A protocol to follow whenever any outside sheep or sheep returning from agistment arrive on your farm should be as follows:

  1. 1

    When the sheep get off the truck and enter the yards, they should be drenched with at least 4 broad spectrum drench groups. Note: If the animals are unfit to be drenched straight away, they should be given access to water and hay in the yards for 24 hours to allow them to recover before the drenches are given. See Tables 1 and 2 in regard to the types of drenches that can be applied depending on the situation.

  2. 2

    Once the sheep have been drenched, they need to be left in the yards (preferably on dirt) for 1-3 days to allow for the worm eggs that have been produced by the worms prior to drenching to be deposited on the paddock. Sheep need access to feed and water during this time. If the animals are kept in a holding paddock with grass, avoid grazing this paddock with sheep for a minimum of 3 months, but ideally longer.

  3. 3

    After the sheep have been in the yards for 1-3 days following drenching, they should be placed onto a paddock that has been recently grazed, preferably by young sheep from the farm. This is so the new animals will become infected with the farm’s worms and dilute out any worms that may have survived the quarantine drenches and reduce the risk of any multi resistant worms (worms that are resistant to multiple drench groups) being deposited onto the pasture.

  4. 4

    Fourteen days after the sheep have received the quarantine drenches, a Faecal Egg Count (FEC) needs to be conducted on the new arrivals to ensure that the quarantine drenches were effective. If any worms have survived four or more different drench groups, they are very resistant, and the animals need to be drenched again. See Tables 1 and 2 regarding which drenches can be used if this occurs, but it will depend on the drenches that were originally given to the sheep.

  5. 5

    If the sheep have come from a known liver fluke area and were drenched for liver fluke as part of the quarantine drenching, collect samples 63 days later and test for liver fluke to ensure that the infection has been removed.

Proposed Quarantine Drench options

Short ESI required:

ESI not a concern:

* Animals from Barber’s pole area, Pole-Vault is a registered trademark of Dalgety Animal Health. **Registered Trademark of Flukazole C *** Registered Trademark of Closicare
† Registered trademark of Tridectin † † Registered trademark of Zoetis † † † Registered trademark of Elanco

Note: Drenches are not to be mixed together and given in a single dose. All drenches must be administered separately at the correct dose rate. Every property is unique and you may require different drench options.


  1. Molento, M.B. et al. (1999). Decreased ivermectin and moxidectin sensitivity in Haemonchus contortus selected with moxidectin over 14 generations. Veterinary Parasitology, 86(1):77-81.
  2. Shoop, W.L. et al. (1993). Mutual resistance to avermectins and milbemycins: oral activity of ivermectin and moxidectin against ivermectin-resistant and susceptible nematodes. Vet. Rec. 133(18):445-7..
  3. Leathwick, D.M. & Besier, R.B. (2014). The management of anthelmintic resistance in grazing ruminants in Australasia – strategies and experiences. Veterinary Parasitology, 204(1):44-54.
  4. - accessed online 08/09/17.
  5. Leathwick, D.M. et al. (2015). Evidence for reversion towards anthelmintic susceptibility in Teladorsagia circumcincta in response to resistance management programmes. International Journal for Parasitology:
  6. Drugs and Drug Resistance, 5(1):9-15.

*Premium drenches include: Startect, Zolvix , Zolvix Plus and commercially available 3 and 4 way combination drenches

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