Environmental and Serological Monitoring of Porcine Circovirus by Loop-Mediated Isothermal Amplification in Pig Farms

Despite the widespread use of Porcine circovirus type 2 (PCV2) vaccination, subclinical infection persists and remains a concern due to its economic impact. Therefore, continuous herd-level monitoring is essential to assess the dynamics of this infection on farms and minimize its impact. This study evaluated the applicability of a loop-mediated isothermal amplification (LAMP) assay for PCV2 detection in serum, air, and surface samples collected under field conditions. In addition, a simplified Direct LAMP protocol, omitting DNA extraction, was compared with quantitative PCR (qPCR) as the reference method. A total of 360 samples from PCV2 vaccinated and unvaccinated fattening farms were analyzed. Diagnostic performance was assessed in terms of sensitivity, specificity, predictive values, and concordance with qPCR, using Cohen's kappa coefficient (κ). LAMP showed higher agreement with qPCR (κ = 0.52) than Direct LAMP (κ = 0.16). Serum samples provided the most reliable results when DNA extraction was performed, reaching substantial agreement with qPCR (κ = 0.76). However, Direct LAMP applied directly to serum was negatively affected by inhibitory substances, resulting in a significant drop in sensitivity. In contrast both air and surface samples yielded comparable results between LAMP and Direct LAMP, without the need for DNA extraction. Notably, LAMP-based assays detected PCV2 circulation earlier than qPCR, particularly in environmental samples. These findings demonstrate the potential of LAMP as a practical alternative to qPCR for PCV2 monitoring. While DNA extraction remains essential for reliable detection in serum, Direct LAMP represents a promising strategy for environmental surveillance, enabling rapid, low-cost, and on-farm diagnostics.