A new diagnostic technique has been developed by Scottish scientists to help in the early detection of sheep scab, marking a significant development towards improved monitoring and control of the parasite. This was made possible through an exciting interdisciplinary collaboration looking at new methods of protein expression and production.
The highly sensitive technique, created by a team of researchers from SEFARI consortium members the Moredun Research Institute near Edinburgh and the James Hutton Institute in Dundee, exploits a protein named Pso EIP-1 to detect asymptomatic infestations with very high levels of accuracy. Importantly, it will enable differentiation between vaccinated and infested sheep.
Dr Alasdair Nisbet, Head of Vaccine and Diagnostic development at Moredun, says: “The technical breakthrough that led to this development was a result of a long-standing, productive and highly collaborative relationship between the research groups at these two SEFARI Institutes.”
Sheep scab, or Psoroptic mange, is caused by an infestation with the parasitic mite, Psoroptes ovis, resulting in a severe skin irritation in livestock. The disease is highly contagious and has profound financial and welfare implications in areas where it is endemic worldwide.
Rapid and accurate diagnosis is essential to help control this parasitic disease. Conventional diagnosis involves time-consuming and expensive analysis of the skin or wool of the sheep under a microscope, which lacks specificity and sensitivity. It also often fails to detect asymptomatic cases, which are responsible for spreading the parasite.
To overcome this issue, the team looked at methods of detecting the mite before symptoms occur. They discovered that early infestation by the mite triggers an immune response in the sheep, which leads to the production of antibodies associated with particular proteins that are excreted by the mite.
One particular protein, termed Pso o 2, was found to specifically induce antibodies in sheep blood in the early stages of an infestation and before the appearance of symptoms. It was shown that Pso o 2 is also an excellent vaccine candidate as it triggers antibody production in the sheep, offering a degree of protection against mite infestation.
“Although Pso o 2 is also a promising candidate for the prototype sheep scab vaccine being developed at Moredun, it cannot be used both diagnostically and in a vaccine as vaccinated sheep would give a positive test even if they weren’t infested.” says Dr Stewart Burgess, Principal Investigator at Moredun.
However, the recent research between the Institutes has identified, characterised and produced an alternative protein, Pso EIP-1, which can detect asymptomatic infestations with very high levels of accuracy. It also distinguishes between infested animals and those that have previously been vaccinated with Pso o 2.
“Pso-EIP-1 overcomes this problem by allowing us to differentiate between infested and vaccinated animals, without compromising on the sensitivity and specificity of the diagnostic test,” continues Dr Burgess. ”It will provide us with a new diagnostic antigen that can be used once the sheep scab vaccine is commercially available.”
Dr Andrew Love, a Principal Investigator and research leader at the James Hutton Institute, commented: “This is a prime example how interdisciplinary research which straddles animal health, immunology, and biotechnology can be harnessed to solve real life issues such as the monitoring and future treatment of pernicious livestock pathogens, including Psoroptic mange. It is a testament to the strength of the collaboration between institutes.”
The published article can be viewed online in Parasite Immunology.
