Exploration of the prevalence and production impact of Mycobacterium avium subsp. paratuberculosis (MAP) infection in the sheep populations of Great Britain and New Zealand.

MAP infection in sheep causes reproductive failure and increased culling rates; improved diagnosis and farmer awareness needed.

This study investigated Mycobacterium avium subsp. paratuberculosis (MAP) prevalence and production impact in sheep flocks across Great Britain and New Zealand. Using faecal PCR sampling from 162 GB farms and 76 NZ farms, researchers found notably high infection rates: 70% of GB flocks and 88% of NZ flocks tested positive for MAP. The research revealed significant associations between MAP faecal shedding and reproductive failure, with infected animals demonstrating a threefold increased risk of pregnancy loss as determined by ultrasound diagnosis. Additionally, MAP-positive flocks exhibited significantly elevated replacement rates compared to uninfected flocks. These findings demonstrate that MAP infection substantially impacts lamb production through forced culling of reproductively compromised ewes, resulting in increased replacement costs and reduced lifetime productivity per breeding animal. While effective control strategies exist for MAP management in sheep flocks, their implementation remains suboptimal due to inadequate disease recognition, diagnostic underutilization, and limited farmer awareness regarding the pathogen's flock-level economic consequences. The authors emphasize that improved diagnosis and understanding of MAP's production-limiting effects are essential for enhancing flock sustainability and profitability in commercial lamb operations.

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