Learn about when you should administer a quarantine drench, what to use, and importantly – what to do afterwards!
The ‘why’ of quarantine
The aim of a quarantine drench to bought-in stock is to prevent the importation of multi-drench-resistant worms onto your property.
You probably have worms with some level of drench resistance already – but you want to ensure you don’t make this worse by importing worms with nastier genetics than the ones already there!
Bought-in lambs and calves represent the biggest risk of importing drench-resistant worms, but those buying in replacement ewes of unknown status should also have a properly thought-out quarantine protocol in place.
Do they need a quarantine?
Note: The following is not an exhaustive list – it’s a set of examples that you may find helpful.
| Definitely | Young stock (lambs or calves) that have already had several combination treatments. Lambs or calves from vendor of unknown or poor drench resistance status. Large line of any sheep from property with unknown or poor resistance status. Calves from large scale rearers, unless vendor can provide you with drench testing data to show that the common drench classes are highly effective. |
| Maybe | Beef weaners from cow breeding system (these are generally low drench use systems and have low risk of developing resistant worms). Cattle in the 1 year – 2 year age group with a history of high drench use (e.g. dairy beef or dairy heifers) – poorly grown ones could easily have production-limiting resistant worms on board, big well-conditioned ones; less so. |
| Probably not | Individual 2th sire rams (a small number of animals won’t bring in enough worms to change your status). Adult cows. Adult bulls. |
What with?
Given there are a small number of farms that now have diagnosed resistance to the ‘novel’ drenches Monepantel+Abamectin (Zolvix®) or Derquantel+Abamectin (Startect®), the safest quarantine treatment is ‘a combination of FOUR unrelated actives, one of which should be a novel drench’.
In practical terms this means a Zolvix® or Startect® administered at the same time as a BZ/Levamisole combination drench. Do not mix together as there may be issues with incompatibility that make the treatment ineffective.
When two drench products are used at the same time, an extended meat withholding period may apply. Speak to your veterinarian for guidance.
Drench new arrivals with either Zolvix or Startect. FEC sample mob in 7-10 days to ensure that treatment has been successful. If there are eggs present, contact your animal health advisor for advice on further treatment of the mob, and management of the paddocks they’ve been grazing. You’ll need to ‘clean up’ those paddocks whilst ensuring the resistant worms don’t get spread further.
Use a triple or double combination drench. Unless the vendor has established no/very low drench resistance via a recent FECRT. In which case – do you need a quarantine at all?
Of the novel drenches, only Zolvix is registered for cattle. If you are buying calves from a large-scale intensive rearer, and they can’t provide you with drench efficacy data, you may want to consider Using a 4-way combination of Zolvix, PLUS a BZ/Levamisole combination, as described above in ‘Sheep – Gold standard is a 4-way drench’
R2 and older cattle typically have very low egg faecal egg counts and are unlikely to contribute high numbers of resistant worms to pasture after treatment. For this reason, it is generally recommended to treat R2 and older cattle on the basis of what they might need for their own health and production, versus a gold standard quarantine. Stressed, undergrown or sick R2 cattle may have higher egg counts – these may be passing more eggs – consider using Zolvix if bringing these in.
Protocol – as important as the product
- Drenching with a flash product could be useless if the quarantine procedure isn’t managed properly.
- Your drench does not kill worm eggs – only adults and larvae.
- You need to be mindful of the eggs that will continue to pass out of your new stock until the worms that are laying them are dead.
While a highly effective quarantine drench will knock out the adult and immature worms in the gut within say 12 hours of dosing, it may take much longer for the eggs already laid to pass out of the animal.
So there will be a period of time (1–3 days) where your highly effective drench has killed all the adults and larvae, but there are still resistant eggs passing out in the faeces.
Gold standard on arrival
New arrivals are held in a bare yard or on grating, with feed and water available, for 24-48 hours. Eggs that pass out and hatch into larvae have no moisture and no grass blades to live in, so they perish. This is easy to do for calves and dairy lambs who are used to eating supplement. For other lambs, it can be tough. Some finishers provide lambs with high quality silage for them to pick at. Others can organise the lambs to be dosed before they leave the vendor, such that 24 hours has elapsed by the time the lambs arrive.
‘Compromise’ on arrival
Newly arrived young stock are put into a specific quarantine paddock for 24-48 hours. This is then not grazed with the same species for many months. For instance adult cattle are the only stock that graze a lamb quarantine paddock for 6 months. This system is easy to manage if new arrivals are only coming in over a short period. If new arrivals come in over a long period, you risk creating a ‘resistant worm hotspot’ that will be harder to clean up, and where ‘super-resistant’ worms might arise. Earmarking a quarantine paddock for immediate spray-out and cropping is another possible solution.
Beyond the first 24 to 48 hours
Graze new arrivals on ‘well contaminated’ areas of the farm for at least a few days – any resistant eggs that pass out should be ‘diluted’ by the mixed worm population already present. Certainly don’t put quarantine drenched stock onto new grass or other low-contamination areas.