Watching your sheep scratching in the field isn’t a pleasant sight for any sheep farmer. But why are they itchy? There are various reasons why sheep suffer itchy skin including lice, flystrike, bacterial infections but most commonly scab.
Sheep scab costs the UK sheep industry approximately £100 million every year with an estimated 10,000 outbreaks in the UK every year. Not only is scab a nuisance but it has significant impacts on animal welfare, daily liveweight gains in lambs and adults and significantly reduces wool and skin quality.
Psoroptes ovis is the mite responsible for causing all this scratching. Females live on the sheep for up to 40 days, laying 1 or 2 eggs every day. These eggs develop into adult mites within 2 weeks. So, it isn’t long until a sheep is covered. Not only do these mites live on the sheep but they can live in wooden fences and hedgerows for up to 16 days! This means your grazing areas can be contaminated too – making sheep scab a disease that is incredibly successful at spreading rapidly and infecting many sheep in a very short space of time. Sheep become extremely itchy after being infested with this mite due to being allergic to the mites themselves and their faeces. This leads to sheep scratching and biting at their flanks, experiencing wool loss and scabs forming on their skin.
Prevention is better than cure when it comes to this skin scratching mite. All sheep entering your flock should be considered a risk and isolated from the rest of the flock for a minimum of 3-4 weeks. This gives the mites time to reveal themselves clinically. If time is not on your side, then diagnostic tests such as skin scrapes or a blood test can be used to indicate if infection is present as early as 2 weeks after initial infestation.
There are only 2 viable options when it comes to control and treatment of sheep scab. Both options involve lengthy meat withdrawals, so it is important to make yourself aware of withdrawal timings prior to performing any control or treatment protocols.
- Plunge dips with Diazinon as an active ingredient. Dips can only be performed by licensed technicians who have a certificate of competence. Dipping can protect your flock for as long as 8 weeks (56 days) and it also prevents and treats blowfly strike, ticks, keds and lice. Remember, jetting and showering is not effective against sheep scab and is not permitted.
- Injectable Macrocyclic Lactones (3-ML). There are various options from this 3-ML group which deliver varying degrees of protection against scab. This group are also effective against roundworm infestations, so it is important to be aware of the risk associated with resistance due to overuse of these products. Scab treatment-only options include Ivermectin or Doramectin based products which may require multiple administrations. If treatment and control is something you want to achieve, then using Moxidectin 1% or 2% injection are the best options giving 28 days and 60 days of prevention respectively.
If your head is scratching worrying about scab, visit your local Fane Valley Stores and speak to one of our Registered Animal Medicine Advisors
