A new study has used a blood test to identify persistent sheep scab infestations in flocks where clinical signs of the disease had not been noticed before.
Researchers from the University of Bristol blood sampled sheep from 254 flocks in three areas across England that were known to have a high prevalence of scab.
Positive results came back for 26% of the flocks, which indicates that a scab infestation is either ongoing or has recently been present in the flock.
However, only 17% of the flock owners had noticed clinical signs of scab in their sheep during the previous year.
“Scab infestations may have persisted in these flocks undetected for a prolonged period. This is a critical point, because sheep from these flocks may be sold or moved around the country and act as carriers for scab infestation,” the researchers state. Scab is a highly contagious disease in sheep which is caused by a mite. It can lead to itching, wool loss, reduced animal performance and welfare issues.
In particular, the scientists identified 20 flocks where scab had been “consistently undiagnosed”.
In these flocks, positive blood tests were returned, but clinical signs of scab had not been reported in the past eight years.
The study, which was published in the scientific journal Parasites & Vectors, states that these flocks were mainly located in hill areas in the north of England, and this could help explain why scab went undetected.
“Hill breeds of sheep may show fewer clinical signs than lowland breeds and sheep grazing commons may only be inspected closely when sheep are periodically gathered,” the research paper claims.