Sheep scab is caused by the mite Psoroptes ovis. They feed off the skin by borrowing into it, which does not in itself cause the classic signs of scab – intense itching. This in fact is caused by a reaction between the faeces of the mite and the skin. This is why itching does not normally stop straight after treatment but continues until all mites and faeces have dropped off.
It is highly contagious and is usually transmitted by direct contact with an infested sheep and is most commonly introduced by bought in animals and strays. However, the mite can live off the sheep for up to 17 days so environmental exposure is also a risk. Contaminated fields, handling facilities, shared equipment, transport and even human contact can all lead to the spread of infection.
Recently infected sheep may not show clinical signs immediately so when introducing bought in stock they should always be treated as infected. They should be quarantined and treated in line with your quarantine protocol.
Sheep scab must be diagnosed by a vet so they can rule out other potential causes of the itching such as lice. In order for scab to be diagnosed superficial skin scrapes need to be taken from the edges of the scabs and the mites, then need to be identified under a microscope. Thousands of sheep are treated every year despite not being diagnosed by a vet. This leads to a waste in time, money and increase the risk of resistance in the future.
Leaving sheep scab undetected or undiagnosed will increase the risk of transmission as well as lead to huge animal welfare implications, poor performance and carcass condemnation at the abattoir. Infestations can be very debilitating causing significant losses of condition, secondary infections, hypothermia and eventually death.
Unfortunately, sheep scab is becoming more prevalent in UK flocks. Part of the reason for this is the sheep scab mite is becoming resistant to the usual drug of choice, Moxidectin. If you suspect that your sheep are infected with scab do not guess or delay. Contact us as soon as possible to discuss what actions you need to take.