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

## TL;DR

This study shows that a simple and fast test called LAMP can detect a virus in pigs on farms, especially in air and surface samples, without needing expensive lab equipment.

## Contribution

The study introduces a simplified LAMP protocol for on-farm detection of PCV2 in environmental samples without DNA extraction.

## Key findings

- LAMP showed substantial agreement with qPCR in serum samples when DNA extraction was performed.
- Direct LAMP without DNA extraction was effective for air and surface samples but less reliable in serum.
- LAMP detected PCV2 earlier than qPCR in environmental samples.

## Abstract

Porcine circovirus type 2 (PCV2) infections have a significant economic impact on pig production. Environmental and serological monitoring on farms is essential for controlling this viral disease. This study evaluated the use of a molecular technique called loop-mediated isothermal amplification (LAMP) for monitoring PCV2 in serum, air, and surface samples. This technique does not require specialized equipment and can be used on the farm itself, allowing it to be applied in monitoring programs without the need to send samples to a molecular biology laboratory.

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.