Expected benefits:

• Keeping iceberg diseases out will avoid production losses and maintain welfare and longevity of breeding stock. Absence of disease in homebred replacements.
• Absence of disease in stock for sale. High health status may add value.

Prerequisites and/or limits:

• Quarantine facilities must be available.
• Effective boundary biosecurity is important.
• Due to costs it may be necessary to decide which disease(s) are priority and focus on these.
• Absence of a diagnostic blood test for OPA.
• Ultrasound scanning of lungs does not a guarantee of freedom from OPA.
• Test sensitivity and specificity lower than ideal due to the nature of the diseases e.g. CLA and Johnes.
• Cost of the testing in relation to the value of the animal.

Cost Benefit analysis

The impact of iceberg diseases within a flock varies hugely. The economic benefits of employing biosecurity measures will depend on multiple factors including: flock prevalence, which iceberg diseases are involved, the type of sheep farm, the ability of the farm to quarantine and test stock, and the costs of screening for disease.
It is not possible to screen incoming animals for some iceberg disease with adequate sensitivity and specificity to completely eliminate the possibility of purchasing in diseased stock. Not purchasing in added animals would be a better solution but is not suitable for all farms.

Sustainability analysis

This solution improves feed efficiency per ewe, as Johnes disease will impact nutrient absorption in the gut. Less supplementary feed may also need to be given as ewes will retain body condition score better.