Sheep scab can become more apparent in flocks during the lambing season, particularly as ewes are brought into close proximity in groups and are monitored more intensely.
This winter, a number of farmers have reported outbreaks of sheep scab in their flocks and as a result, Northern Ireland-based group Animal Health and Welfare NI (AHWNI) have offered farmers advice on identifying and treating sheep scab in their flocks.
Mite populations can build up under wool in the winter, and the combination of the demands of pregnancy, poor weather and itching caused by the scab mite can lead to rapid loss in appetite and body condition.
This can leave the ewe vulnerable to twin-lamb disease, a poor supply of colostrum at the point of lambing and lambs with birthweights lower than expected.
Additionally, feeding at troughs or housing sheep will create ideal conditions for the rapid spread of the sheep scab-causing mites through the flock and from one batch of sheep to the next.
Mites can be transferred on clothing to sheep, for example, during direct contact at feeding.
Signs of sheep scab include:
- Obvious restlessness in the flock;
- Sheep scratching against fence posts;
- Stained areas of wool;
- A pulled wool appearance leading to wool loss;
- Head tossing;
- Attempted biting.
According to AHWNI, correct diagnosis is essential, as there are similarities in the clinical signs seen in cases of sheep-scab mites and lice, however treatments will differ.
If left unchecked, any scab in a flock will rapidly transfer to the lambs as they are born and it will
be necessary to treat all the lambs as well as the ewes.
Treatment
Outbreaks in flocks on the cusp of lambing or during lambing present challenges to the use of organophosphate (OP) dips, given the young age of lambs.
In general, dipping can be undertaken safely in pregnant sheep, however it is essential not to rush the process, according to AHWNI.
Ewes should be gently lowered into and assisted through and out of the bath and
any lambs should be dipped separately from ewes.
Dip is not suitable for sheep that are being milked for human consumption.
The ewes will have protection for 60 days so optimal timing must be considered, for example, in
case it is worth waiting for a short time until all lambs are born and are a manageable size.
Injectable products are available but, particularly at this time of year, consideration must be given to using a product with sufficient persistence of effect, as truly scab-free fields and sheds to house sheep in after treatment need to be identified as mites can survive in the environment for up to 17 days.
Accurate treatment of every sheep is essential and the chances of some of the mites being resistant to the injectable products must not be underestimated.
SOS Sheep Scab Research Project
A Biotechnology and Biological Sciences Research Council-funded research project is currently running throughout Northern Ireland where participants nominate a private vet who will be funded to undertake a farm visit, investigate if sheep scab is likely to be present in their flock and provide advice to the farmer.
If their vet recommends that treatment is required, the project will fund the supply of prescribed medicines up to a reasonable limit.
The costs of application of dip or treatment with injectables will be borne by the flock owner, and 90 flock owners have engaged with the scheme so far.
Sheep farmers in Northern Ireland who have seen clinical signs of sheep scab in their flock may be eligible to participate in the project and can find out more by contacting AHWNI.