There are only two treatment choices for scab – an endectocide (injectable) or an organophosphate dip (diazinon). Resistance in scab mites to the injectables has been confirmed in the UK, which means we need to be increasingly careful about how we use both treatment choices. Action is needed to both slow the rate of resistance to injectables and ensure mites do not develop resistance to OPs - more information here.
If you have treated sheep and they still appear to be infected (i.e. they are itching) it is important to report it to your vet and/or merchant. Do no just retreat, as this could waste your time and money and further add to resistance developing.
SCOPS has developed a simple protocol to go through when a treatment has failed. This is designed to:-