A survey of NI sheep farmers has found that 36% of respondents had at least one outbreak of sheep scab during the last five years.

Almost three-quarters of outbreaks were attributed to bought-in stock introducing the disease and the second most common cause was contact with neighbouring flocks.

The new research, published in the scientific journal Preventive Veterinary Medicine, indicates sheep scab is “widely dispersed and endemic” across NI.

The survey was led by local vet Paul Crawford as part of a research project at Harper Adams University.

“These findings have provided evidence of the widespread nature of sheep scab in the NI flock, and of the knowledge gaps and behaviours which need to be addressed to improve sheep scab control,” the research paper reads.

Clinical signs

In particular, Crawford found 64% of respondents incorrectly thought that a three-week quarantine period for bought-in stock is sufficient for clinical signs of scab to appear.

The paper states that scab can have a “long incubation period” where there is a delay between infestation and clinical signs.

Also, some sheep can be “latent carriers” so they do not show symptoms of scab but can still spread the disease.

“This creates the opportunity for undetected, infested sheep, to spread sheep scab within the main flock before clinical signs develop,” the paper reads.

The researchers recommend more widespread use of a relatively new blood test, which is reliable and can detect scab within two weeks of infestation.

Highly contagious

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.

Across the survey respondents who had an outbreak, injectable wormers were the most popular treatment option, used nearly twice as often as plunge dipping with organophosphate (OP) products.

Another concern raised by the survey was a quarter of respondents wrongly thought mobile shower units were recommended for scab control and 11% incorrectly said pour-on products were effective.

Neither shower units or pour-ons are recommended for prevention or treatment of sheep scab.

In fact, it is illegal to use OP-based products in mobile shower units.

The research paper states that common misconceptions about the use of OP dips needs to be “challenged urgently” as the products are only fully effective in plunge dippers.