Economic viability of different surveillance strategies for the control of paratuberculosis in Swiss dairy cattle.

Paratuberculosis (PTB), or Johne's disease, is a globally prevalent disease caused by Mycobacterium avium subsp. paratuberculosis, leading to significant economic losses in the dairy industry. This study assessed the economic viability of potential PTB surveillance strategies in Switzerland using stochastic simulation models.Two non-targeted surveillance strategies (SS1 and SS2) were assessed under three participation scenarios over ten years. Additionally, a more targeted surveillance strategy (SS3) was evaluated, focusing on historically positive herds.In SS1, herds are screened using sock swab PCR followed by individual faecal PCR testing in sock swab-positive herds. SS2 follows a risk-based approach: in high-risk herds (i.e., previous PTB cases or animals with suggestive symptoms), all cows older than 24 months are tested using serum ELISA, with faecal PCR confirmation. In other herds, only high-risk cows (somatic cell count >200,000/ml or >3 lactation) undergo ELISA testing to determine herd status.In SS3, only animals from herds with recent outbreaks or clinical cases are tested.Neither of the two non-targeted strategies (SS1 and SS2) proves economically beneficial over a ten-year period, with Benefit-Cost Ratios (BCR) below 0.1. In contrast, the targeted strategy (SS3) achieves a BCR of 1.42, a net present value of CHF 568,545, and reaches the break-even point after seven years.These results indicate that targeted control strategies are more economically viable in low-prevalence settings.