**HERALD (Health Enhancement through Rapid Assessment of Livestock Diseases)** is a collaborative project delivering fast, practical diagnostics for Johne's disease (JD) in cattle, with limited feasibility work preparing the platform for future bovine tuberculosis applications. JD is widespread and costly for dairy and beef producers, undermining animal welfare and farm profitability. Current widely used diagnostics identify **only around 20% of infected animals**, delaying critical management decisions. JD-affected herds show higher somatic cell counts and increased mastitis risk. Farmers and vets need tools that identify infection long before visible signs or productivity losses appear. HERALD's solution is a dual-format diagnostic platform **built on novel mycolic-acid antigens** to detect disease antibodies in serum: * **A high-throughput screen ('ELISA')** for veterinary laboratories to screen large groups efficiently * **Rapid lateral flow test (LFT)** providing same-day, cow-side results for immediate management decisions To accelerate adoption and support evidence-based planning, the project will create a **free, open-access JD database** with anonymised prevalence information and benchmarks for farmers, vets and programme managers. Proof-of-concept studies indicate these proprietary antigens deliver higher sensitivity and enable earlier detection than existing commercial tests, identifying infection years before symptoms, transmission or productivity losses occur. **One Health Benefits:** JD is caused by _Mycobacterium avium_ subsp. paratuberculosis (MAP), which has also been detected in **20-50% of Crohn's disease patients** compared to lower rates in healthy individuals, with both diseases sharing remarkable clinical similarities. MAP appears in **2% of pasteurized milk and 9% of infant formula**, as it resists pasteurization, potentially exposing humans through the food chain. There are considerable efforts to move to 'Johne's free herds'. HERALD's database will provide high-quality field data informing future research and public-health dialogue. **Welsh Innovation Leadership** HERALD represents collaboration between Welsh companies and a specialist English lateral flow manufacturer, combining expertise in biochemistry, AI, and veterinary science. Most work will be conducted in North Wales, supporting local innovation and economic impact through Welsh farmers/vets and the MSParc Agritech Cluster. **Expected Outcomes** HERALD will deliver a laboratory-based ELISA for early detection of JD infection, validated on \>1300 serum-samples (600 this project), a prototype on-farm LFT, initially for specialist applications, an operational open database, and technical groundwork for commercial launch. Benefits include reduced JD spread, lower mastitis burden, improved milk quality and animal welfare, and support for responsible antimicrobial use. This breakthrough platform positions Wales as a global leader in livestock diagnostic innovation while addressing farmer needs and supporting One Health.