#05-139

Complete

Date Full Report Received

10/09/2006

Date Abstract Report Received

10/09/2006

Investigation

Institution:
Primary Investigator:
Co-Investigators: Kyoung-Jin Yoon, J. D. Schneider

The effectiveness of decontamination procedures and downtimes in reducing PRRSV and bacterial contamination of wean-finish and nursery rooms of a commercial swine farm was tested. The herd was infected with a low pathogenic strain of PRRSV causing pigs to seroconvert to PRRS. Pigs in the herd were not vaccinated for PRRSV. During this study, pigs in the nursery did not demonstrate any signs of PRRSV infection. Pigs in the finisher were recovering from PCVAD. Rooms were decontaminated by farm employees. Pigs were moved out of each room and the room was power-washed with water to remove gross contamination. Each room was disinfected according to label directions with one of four classes of disinfectants: phenolic (Biophene Liquid Disinfectant, 0.5 ounce per gallon), quaternary ammonium (Biosentry 904, 0.5 ounce per gallon), peroxygen (Virkon S, 1% solution), glutataldehyde/quaternary ammonium (Synergize, 0.5 ounce per gallon). Rooms were left empty for 2 (nurseries) or 3 (wean-finish) days following disinfection. Swab samples of plastic, concrete, and stainless steel surfaces were collected before cleaning, after cleaning, after drying, immediately after disinfection, and 2-3 days after disinfection. Median bacterial counts per cm2 of surface were calculated and the presence of PRRSV RNA and PRRSV was determined using rRT-PCR and virus isolation tests, respectively. Thirty-nine percent of nursery pigs were seropositive to PRRSV at sampling. PRRSV RNA was detected in saliva samples of 26% of nursery pigs with at least one positive pig in each room, indicating PRRSV exposure and the potential for shedding of PRRSV. Virus, however, was not isolated from any pig saliva samples, indicating that PRRSV might not have been shed in saliva during the study or that the virus had been shed but was degraded by salivary enzymes and was not infectious. Ninety-five percent of finishing pigs were seropositive to PRRSV at sampling. PRRSV RNA was not detected in any pig saliva samples, nor was virus isolated from any pig saliva samples. PRRSV was not detected by rRT-PCR or virus isolation technique on plastic flooring or concrete slats at any of the time periods sampled. PRRSV RNA was detected by rRT-PCR on one stainless steel feeder sample prior to cleaning and on another staineless steel feeder sample after disinfection; however, PRRSV was not isolated from any of the stainless steel samples. Thus, PRRSV was determined to not be an environmental contaminant on this farm. Bacterial contamination of surfaces varied with plastic flooring generally being the most contaminated and stainless steel being the least contaminated. Differences in contamination levels were likely due to surface orientation (horizontal versus vertical) and surface smoothness (i.e. porous versus nonporous). Thorough cleaning of surfaces and allowing cleaned surfaces to dry provided the greatest decrease in bacterial counts. Further decreases in bacterial counts were not observed after disinfection, regardless of disinfectant class used or surface type. Reductions in specific pathogens could have occurred following disinfection; however, we did not test for disinfectant efficacy against specific pathogens in this study. Future studies should test the field efficacy of disinfectants against specific environmental contaminants that naturally occur on swine farms. Until future studies are completed, the authors continue to promote the use of disinfection as a disease control strategy to kill specific pathogens on the farm. Results of the effectiveness of downtime were not consistent. A 2-day downtime reduced bacterial contamination on plastic flooring but a 3-day downtime increased bacterial contamination on concrete. The 2-day downtime could have been long enough for drying of bacteria to occur but not long enough for recontamination of the flooring. Concrete slats are horizontal surfaces with many crevices. Three days could have provided enough time for recontamination of the surface by bacteria settling from any air or dust entering the room. Further studies are needed to determine between the value of downtime length with respect to surface type. Contact Information: Dr. Sandra F. Amass Purdue University, VCS/Lynn 625 Harrison Street West Lafayette, IN 47907-2026 Phone: 765-494-8052 Fax: 765-496-2608 email: amasss@purdue.edu (note 3 s’s in email)