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 Kansas State University researchers Harrison, Houston, Blomme, Otott, Bai, Poulsen Porter, Woodworth, Paulk, Gebhardt, and Jones share the findings of their study evaluating the efficacy of two types of boot baths in reducing PEDV and PRRSV detection rates.
Background: Boot baths have been implemented to limit pathogen spread within swine facilities; however, there are concerns regarding the overall efficacy of these methods. The objective of this study was to evaluate the efficacy of boot baths in reducing the quantity of detectable PEDV and PRRSV genetic material using wet or dry disinfectants.
Materials and Methods: The treatments included 1) control; 2) dry chlorine powder; and 3) wet quaternary ammonium/glutaraldehyde liquid. Prior to disinfection, rubber boots were inoculated with 1 mL of co-inoculants of PRRSV (1×105 TCID50/mL) and PEDV (1×105 TCID50/mL) and dried for 15 min. After the drying period, a researcher placed the boot on the right foot and stepped directly on a steel coupon (control) or stepped first into a boot bath containing either the wet or dry sanitizer, stood for 3 s, and then stepped onto a steel coupon. After one min, an environmental swab was then collected and processed from each boot and steel coupon. The procedure was replicated 12 times per disinfectant treatment. Samples were analyzed using a duplex qPCR at the Kansas State Veterinary Diagnostic Laboratory.
Results and Discussion: A disinfectant × surface interaction was observed for both the proportion of samples PCR positive (P < 0.05) and the quantify of detectable RNA, or Ct value (P < 0.05; Table 1). More PCR positive samples, regardless of virus type, were found on the boot and steel coupon of the control treatment and the boot of the wet disinfectant than the steel coupon of the wet disinfectant, leading the detectable viral RNA to follow a similar pattern. There were no PCR positive samples from either surface when the dry disinfectant was used. A boot bath containing the dry disinfectant surpassed the performance of wet disinfectant. While the wet disinfectant reduced the quantity of viral RNA compared to the control, it did not reduce viral RNA of either virus beyond detectable limits. While these results aid in understanding the efficacy of certain boot bath disinfectants, it does not account for the buildup of organic matter in boot bath nor the infectivity of these samples if utilized in a live animal production setting.
The full paper can be found at: https://pubmed.ncbi.nlm.nih.gov/36519006/