Thirty-two, 4-week-old barrows were inoculated via oral gastric tube with 5 mL of either PEDV-negative feces for a negative control (Neg), untreated PEDV-positive feces for a positive control (Pos), or PEDV-positive feces that was subjected to 71°C for 10 minutes (71C-10M), 63°C for 10 minutes (63C-10M), 54°C for 10 minutes (54C-10M), 38°C for 12 hours (38C-12H), 20°C for 24 hours (20C-24H), or 20°C for 7 days (20C-7D). These pigs served as a bioassay to determine the infectivity of virus following treatment. Infectivity was determined by detection of virus with reverse transcriptase polymerase chain reaction (RT-PCR) on fecal swabs collected from the inoculated pigs on days 3 and 7 post-inoculation.
None of the pigs in the 71C-10M and 20C-7D groups became infected with PEDV. All of the other combinations of time and temperature had one or more pigs infected with PEDV. Twenty-five percent (1/4) of the pigs in group 63C-10M, 54C-10M, and 20C-10M; 50% (2/4) of the pigs in group 38C-12H and 100% (4/4) of the pigs in the positive control group become infected. These results suggest that even when feces is present, heating livestock trailers to 71° C (160° F) for 10 minutes or allowing them to sit for 7 days at room temperature (68° F) was sufficient to prevent transmission of PEDV present in feces. None of the other combinations of time and temperature: 63° C (145° F) and 54° C (130° F) for 10 minutes, 38° C (100° F) for 12 hours, and 20° C (68° F) for 24 hours were 100% effective at inactivating PEDV in feces. Appropriate TADD protocols may be effective at inactivating PEDV in trailers where fecal matter and bedding has been removed by scraping or when some organic matter is present following power washing and disinfection.
For farms, systems, or trucking companies that are unable to wash, disinfect, and dry trailers due to the constraints, removing the feces and bedding by scraping and subsequently heating may be practicable. The investigators do not propose that this is a preferred alternative to thoroughly washing, disinfecting, and drying trailers. Rather, this work demonstrates the value of possible alternatives when washing, disinfection and drying cannot be accomplished to reduce the risk of transmitting PEDV between groups of animals.
Contact information for correspondence:
Dr. Derald Holtkamp DVM, MS
Associate Professor, Iowa State University College of Veterinary Medicine
Business: (515) 294-9611
Mobile: (515) 520-1040
2233 Lloyd Veterinary Medical Center
Ames, IA 50011-1250