Risk factors for Classical Scrapie transmission in Iceland: Insights from a countrywide farm survey

Introduction: Classical Scrapie is a fatal neurodegenerative disease affecting sheep, with significant consequences for animal welfare and the economic sustainability of sheep farming. Despite long-standing eradication efforts, outbreaks continue to occur in certain Icelandic regions.

Objectives: This study aims to identify potential risk factors contributing to disease transmission by analysing data collected by a questionnaire survey from both affected and non-affected farms across the country.

Methods: A questionnaire survey was carried out with farmers in four regions of Iceland between April 2024 and April 2025. The survey gathered information on farm characteristics (land and flock size), annual management practices, animal movements, use of communal grazing areas, personal contacts and biosecurity measures. This includes a comparison of different regions in Iceland according their specific risk factors.

Results/Discussion: Based on this survey descriptive analysis show that external personnel contacts, shared machinery use, animal movements and shared mountain grazing areas with common gatherings are important factors for disease spread. Larger farms with higher animal density and on-farm carcass disposal were also more frequently associated with Scrapie-affected holdings. In contrast, protective factors included limited animal and personnel movement, the use of artificial insemination, genetic selection for resistance and use of secured disposal methods. Regional differences in farm structure and biosecurity measures also influence disease dynamics.

Conclusion: To support future eradication efforts, improving biosecurity, strengthening resistance breeding, safer carcass disposal and regional awareness of risk factors are essential.