This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
In this week’s Science Page we take a look at a study by Claudio Marcello Melini, Amanda Palowski, Declan C. Schroeder, and Cesar A. Corzo evaluating PRRSV viability on various surfaces found in growing sites.
Key points
- Viable PRRS virus can be detected on environmental surfaces collected from different surfaces.
- A total of 48 samples across six farms contained viable PRRS virus, with non-porous materials testing positive more frequently.
Introduction
Most growing pig sites do not have the same level of biosecurity as breeding herds and lack basic measures such as shower-in/shower-out and D&D rooms, creating an opportunity for PRRSV indirect transmission to occur. Identifying viable PRRSV on frequently touched surfaces may offer additional insight for biosecurity protocols. This study aimed to 1) determine whether viable PRRSV can be detected on frequently touched surfaces by farm personnel; 2) assess whether the number of PRRSV detections from oral fluids in a population are associated with viable PRRSV detections on farm surfaces; and 3) explore the agreement between standard and viability RT-qPCR.
Materials and Methods
Ten PRRSV-positive growing pig farms were enrolled in this cross-sectional study. A total of 20 samples per farm from different surfaces were collected by rubbing the surface with a media moistened pad and then placing the pad in a resealable bag, squeezing it and pouring the liquid into a tube. In addition, a set of 8 ropes (representing 16 pens) per barn were hung to collect oral fluids and tested for PRRSV RT-PCR. Environmental samples were tested via viability and conventional RT-qPCR.
Results and Discussion
PRRS virus RNA was mostly detected in 80 out of 200 environmental samples (Fig 1). Viable virus was detected in 48 of the 80 samples across six farms, with non-porous materials testing positive more frequently. There was a negative association (OR = 0.005; 95% CI 0.00, 6.82; p value = 0.18) between the proportion of positive oral fluids and the detection of viable virus in environmental surfaces. Agreement between the detection of RNA and viable PRRSV from surface samples using Cohen’s kappa yielded perfect agreement (κ=1.00) to low agreement (κ=0.29) depending on the surfaces.
Conclusion
This study highlights the fact that farm surfaces can contain viable PRRSV. Therefore, biocontainment measures need to be considered and in place to avoid viral dissemination. The use of viability RT-qPCR to detect viable PRRSV offers a practical tool in field settings to improve biosecurity protocols and reduce indirect transmission of PRRSV in swine production systems.
Read the full paper: https://doi.org/10.1371/journal.pone.0344714