# Space–time distribution of classical scrapie in Italian sheep: assessing the effectiveness of the National Genetic Selection Plan

## TL;DR

This study examines how scrapie prevalence and genetic selection efforts changed over time in Italian sheep, showing a decline after 2016.

## Contribution

The study evaluates the effectiveness of Italy's National Genetic Selection Plan in reducing scrapie through spatiotemporal analysis.

## Key findings

- Scrapie prevalence increased from 2005–2015 but sharply declined from 2016–2022.
- The proportion of susceptible rams decreased steadily from 2005 to 2022.
- Control strategies in Sardinia led to earlier trend shifts compared to the rest of Italy.

## Abstract

Scrapie is a contagious neurodegenerative disease of sheep and goats sustained by prions. The aim of this study was to assess the effectiveness of selective interventions in Italy by describing the temporal trends and geographical distribution (a) of scrapie prevalence and (b) of the application of the National Genetic Selection Plan (NGSP). Poisson models were used to study temporal trends of disease prevalence (in terms of prevalence ratios, PR), whereas NGSP genotyping data from rams tested between 2005 and 2022 were used to study the temporal trend and geographical distribution of the percentage of susceptible animals. In addition, change-point regression analysis was used to identify changes in the trend. The trend in prevalence at the national level shows an increase in the period 2005–2015 (PR = 1.09, 95% CI 1.04–1.15), followed by a sharp decline between 2016 and 2022 (PR = 0.88, 95% CI 0.83–0.93). The proportion of susceptible rams shows a decreasing temporal trend, both along 2005–2022 (PR 0.97, 95% CI 0.96–0.98) and in the two periods (respectively, 2005–2015: PR 0.92, 95% CI 0.89–0.96; 2016–2022: PR 0.94, 95% CI 0.89–0.98). Change-point regression analysis identified a nationwide trend shift between 2015 and 2020, with Sardinia showing an earlier change between 2012 and 2015. The analysis of temporal trends showed geographical heterogeneity associated with different control strategies, especially in Sardinia, where the early targeted interventions in 2009 anticipated most of the provisions of the second NGSP.

The online version contains supplementary material available at 10.1186/s13567-025-01677-8.