#07-119

Complete

Date Full Report Received

11/11/2008

Date Abstract Report Received

11/11/2008

Investigation

Institution:
Primary Investigator:

The objective of this study was to calculate the inactivation of PRRSV by dose of UV254 in a “static” (i.e., virus-in-liquid solution) system. This study is the first step in evaluating the use of UV254 for the inactivation of airborne pathogens in commercial swine facilities. Viruses: The study was conducted using PRRSV isolate MN-184 (kindly provided by Dr. Scott Dee, University of Minnesota) propagated on MARC-145 cells. For comparison and contrast, a Reovirus type 3 (kindly provided by Dr. Cathy Miller, Iowa State University) grown on L929 cells was included in the experiment. Reovirus type 3 is recognized as extremely hardy and highly resistant to inactivation by UV254. Equipment: Commercially-available ultraviolet (UV254) lamps (American Ultraviolet Co., Lebanon IN) were mounted in an environmental chamber (Percival Scientific, Perry IA) capable of maintaining any pre-selected temperature between 0 and 60°C. The dose of UV254 to which the samples were exposed was measured using UV254 radiometer sensors (Technika,Co., Scottsdale AZ). No equipment was purchased through NPB #07-119. The experiment was conducted in the environmental chamber with the temperature held at 4°C. Five samples of each virus were exposed to each of 10 UV254 doses [0.000 (negative controls), 0.025, 0.050, 0.075, 0.100, 0.125, 0.150, 0.200, 0.250, and 0.300 Joules/cm2]. Immediately following exposure, samples were stored at -80°C until assayed. Microtitration infectivity assays were conducted to quantify the amount of infectious virus remaining in each sample post-treatment. Data Analysis: The k-value (inactivation constant) is used to describe the susceptibility of virus to UV254. Higher k-values indicate greater susceptible to inactivation by UV254. The k-value is calculated as the slope of the line describing the inactivation of the virus [ ] where N = initial viral concentration and Nt = concentration following treatment with a specific dose of UV254. The k-values for PRRSV and reovirus were estimated to be 0.0893 and 0.0103, respectively. Conclusions: PRRSV in solution is highly susceptible to UV254 irradiation. These data justify the next phase of this research: evaluation of the UV254 dose required to inactivate airborne PRRSV.