Beth Wells

Project: Development of a diagnostic test for sheep scab based on biomarkers

Type: PHD

Institution: Moredun Research Institute

Sheep scab is recognised as the most important ectoparasitic disease affecting sheep in the UK and is caused by the highly infectious mite Psoroptes ovis. It is a serious welfare as well as a production issue and was recently made notifiable in Scotland, indicating that early diagnostic tests will be crucial for future disease control.

This project aims to develop a test for sheep scab based on proteins present in the blood known as biomarkers. Since the start of the project in October 2009, three proteins have been identified as potential candidates - serum amyloid A (SAA), haptoglobin (Hp) and complement 4 binding protein beta chain (C4BPB).

SAA and Hp have been evaluated using existing assays and their levels have been shown to rise in response to disease progression and decline rapidly to low circulating levels post-treatment. This is imperative for any biomarker as they must be able to distinguish between treated and non-treated sheep. Validation is currently underway using extensive experimental and field samples. For the third protein, C4BPB, the ovine gene has been sequenced, a recombinant protein expressed and currently antibody is being generated in rabbits.

An ELISA will then be developed allowing further evaluation of C4BPB as a potential biomarker. Finally the possibility of integrating the tested biomarkers with the existing antibody assay will be investigated to produce a sheep scab specific diagnostic test which will indicate current disease status.

The benefit to the industry is that it will enable rapid identification of infested animals and indicate when they have been successfully treated. Such a test will be critical in any control or eradication programme where clinical observations alone are unlikely to be sufficient and confirmation of successful treatment will be essential.