Sheep scab, caused by Psoroptes ovis, remains one of the most damaging and costly parasitic diseases, estimated to cost the GB sheep industry £78–202M per year1. Despite sector-wide efforts, it persists due to high infection ability, silent carriers, and mite survival off-host for several weeks. Effective, responsible treatment alongside strong biosecurity is essential to control outbreaks and prevent re-infestations.
Recognising and Managing Scab on Your Farm
Typical signs include intense itching, rubbing, biting, wool loss, raw or scaly skin lesions, weight loss or reduced gain, and restlessness. Beyond welfare concerns, scab reduces productivity via poorer growth, reduced body condition, compromised ewe performance, and added labour and treatment costs.
To maximise outcomes and ensure effective control, follow these pillars:
- Accurate Diagnosis
Confirm scab with appropriate diagnostic testing before treatment. Early cases and carriers may be missed clinically, and other ectoparasites (e.g. lice) can look similar but require different treatments. Work with your vet or RAMA to select the right tests at the right time to avoid misdiagnosis and unnecessary treatments.
- Treat All Sheep
Treat the entire flock (and any in-contact groups) simultaneously to prevent carriers sustaining transmission. With persistent products there is a window to treat all in-contact animals. Plan labour, handling, and gathering to complete treatment within this window. - Administer Correctly
Follow label directions precisely for dose rate and route. Avoid under-dosing and unnecessary repeat treatments that can drive resistance. Combine chemical control with good management: reduce close-contact mingling during risk periods, keep handling areas clean, and manage fence-line contacts.
- Maintain Biosecurity
Isolate new or returning sheep with strict separation. It is recommended to blood test a sample of 12 animals after two weeks in quarantine to detect exposure to scab mites and use results to determine if treatment is needed before mixing. Coordinate with neighbours, markets, and contractors to reduce cross-flock risk.
- Record Treatments and Plan
Keep compliant records of treatments, batches, dates, weights, and outcomes to track efficacy and support your parasite control plan. Your animal health advisor can tailor protocols and reduce resistance risk. While resistance to macrocyclic lactones in sheep scab mites has been confirmed in the UK, actives such as moxidectin remain important; responsible use is vital to preserve effectiveness.
Treatment Options
SCOPS recommends:
- Plunge dipping with an organophosphate (OP) dip.
- Long-acting moxidectin injections when dipping is not an option.
Choose based on infrastructure, labour, handling capacity, environmental and health/safety factors, seasonality, and flock risk. Always follow label instructions and seek professional advice.
Key Benefits of ZERMEX 2% LA
- Single injection to tackle sheep scab.
- Long-acting protection for up to 60 days.
- Simple subcutaneous administration behind the ear.
- Improves welfare by reducing itching, skin damage and stress.
- Supports productivity through better growth rates, wool quality, and overall performance.
Investing in early diagnosis, whole-flock treatment where indicated, robust quarantine, and accurate records can help to improve welfare, productivity, and profitability. By working closely with your animal health advisor, they can help you to tailor a plan best suited to your flock. Find your local Downland Advisor using our handy map here: https://www.downland.co.uk/advisor-map
Newsletter content supplied by Zoetis and sponsored by Zoetis, makers of ZERMEX 2% LA
Reference:
1 Nixon, EJ, et. al., Vet Record, 2020
ZERMEX® 20mg/ml LA Solution for Injection for Sheep contains moxidectin, POM-VPS. May be prescribed by any Registered Qualified Person (RQP - a veterinarian, a pharmacist or an appropriately qualified RAMA). This promotion is only intended for prescribers and farmers in England, Scotland and Wales. For further information see the SPC, farmers should contact their animal medicines supplier, RAMA, veterinary surgeon or Downland Marketing Ltd, Warwick Mill Business Centre, Warwick Bridge, Carlisle CA4 8RR.
Use medicines responsibly: www.noah.co.uk/responsible. Prescription decisions are for the person issuing the prescription alone.
Further information can be obtained from the products SPC/Datasheet, from your medicine prescriber or from Zoetis UK Limited, First Floor, Birchwood Building, Springfield Drive, Leatherhead KT22 7LP www.zoetis.co.uk. Customer Support: 0345 300 8034 Use medicines responsibly (www.noah.co.uk/responsible) Prescription decisions are for the person issuing the prescription alone.
Date of preparation: May 2026. MM-49363