Scientific Abstract

Infected animals shed pathogens into the environment, making environmental sampling a potentially viable approach to surveillance in swine populations.  In particular, continuous environmental sampling offers a practical alternative to traditional point-in-time environmental sampling methods because prolonged exposure provides for aggregating pathogens over time as pathogens dispersed by activity in the barn gradually settle out of the air onto the samplers. 

This study evaluated 9 candidate materials for a low-cost, on-farm sampling system using porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV) as targets.  Two experiments were conducted: liquid recovery (Experiment 1), and RNA recovery (Experiment 2). 

In Experiment 1, 9 candidate materials were assessed for liquid recovery: (1) Whatman® filter paper grade 903; (2) FTA® Cards; (3) Polyester filter paper (Optimice Cage Reemay Filter Media; (4) Swiffer® dry cloth; (5) SmartSolve® water soluble paper; (6) Dry surface filter polyester; (7) Tacky surface filter polyester; (8) Water-soluble starch foam; (9) Sellars® blue shop towels.  Candidate materials were evaluated by soaking them in increasing volumes of PCR-grade water, manually agitating, and then measuring the volume of liquid recovered.  The 3 top-performing candidates from Experiment 1, i.e., materials (1), (2), and (4)  were selected for evaluation in Experiment 2.  FTA® cards (candidate 2) were also included in Experiment 2 in recognition of the fact that FTA® cards are commonly used in diagnostics.

In Experiment 2, the recovery of PRRSV and PEDV RNA was compared among candidate materials.  Specifically, candidate papers were inoculated with fourfold dilutions of each virus, dried, vacuum-sealed, and stored at -80°C before being eluted with PCR grade water, Tris EDTA buffer, or general lysis buffer.  Eluates from the candidates and the dilutions of virus inoculum (control) were tested by RT-qPCR. In Experiment 2, RNA recovery varied by material and elution buffer, with polyester filter paper/lysis buffer achieving superior RNA detection results.  Notably some materials matched or exceeded RNA recovery from the controls.  The findings in this study demonstrated the potential for continuous environmental sampling using specific materials.