Abstract
As pathogens become more prevalent within the swine industry, the demand for methods to monitor and detect them has increased. Using environmental swabbing to detect pathogens in the feed supply chain may allow for a greater likelihood of detection than product sampling. The objective of this experiment was to identify the swab that detects porcine epidemic diarrhea virus (PEDV) from feed manufacturing surfaces at the dose most similar to that included in an ingredient. The experiment was arranged as a 2×2×4 factorial with two doses of PEDV (low: 10^3 or high: 10^5 TCID50), two surface types (stainless steel or polyethylene tote), and four swab types (1: sponge-tip swab packaged with neutralizing buffer; 2: Dacron-tip swab packaged in Dey-Engley neutralizing broth; 3: dry dust-mop; or 4: cotton gauze soaked in phosphate-buffered saline). Soybean meal (SBM) was inoculated with levels of PEDV and placed onto stainless steel for 15 min, then the polyethylene tote. The SBM was removed, surfaces were swabbed with one of four types. Samples of inoculum, SBM, and swabs were analyzed for PEDV via qRT-PCR with three replicates per treatment. Data were analyzed via the GLIMMIX procedure of SAS. There was a dose×surface type×swab type interaction (P < 0.0001; SEM=0.967; Table 1). In stock virus and SBM, increased dose resulted in lower (P < 0.05) detectable PEDV. However, no virus was detected in sponge-tip swabs used on stainless steel surfaces. Dacron-tip and cotton gauze swabs yielded the most detectable PEDV from surfaces, but was still 1.2 to 5.1 Cycle threshold (Ct) higher than SBM. Detectable PEDV in SBM was approximately 11 Ct higher than in stock virus. In summary, environmental swabbing can easily detect PEDV, but at higher Ct than product samples. Of the swabs tested, Dacron-tip and cotton gauze are superior for PEDV environmental analysis than dry mops. Sponge-tip swabs should not be used for environmental monitoring of PEDV.
Keywords: environmental monitoring, PEDV, swabbing