Lessons learned with African swine fever virus in feed biosecurity

Under real-world conditions in a region with endemic ASFV circulation, contamination can be detected on a number of surfaces within the feed mill.


By Jordan T. Gebhardt, Grace Elijah, Jason C. Woodworth, Chad B. Paulk and Cassie K. Jones, Kansas State University; and Steve S. Dritz, PIC

via National Hog Farmer - Nov 12, 2020


The swine and feed industry have experienced significant pressure to enhance biosecurity practices in recent years, with initial focus developing after the introduction of porcine epidemic diarrhea virus into North America. With recent evidence that feed could also serve as a means for transmission of foreign animal diseases such as African swine fever virus, a renewed emphasis has been placed on continued improvement of biosecurity practices implemented within the swine feed sector.


In an effort to understand what best practices can be implemented to reduce the potential transmission of ASFV within an active outbreak region, a collaboration with partners in Vietnam was established to use a science-based approach to evaluate and identify potential gaps in biosecurity practices.


As part of this investigation, a variety of sample types were collected from a feed mill including feed and ingredient samples and environmental samples collected from surfaces within the feed mill, exterior surfaces of feed delivery trucks, and interior cab surfaces including foot pedals and the steering wheel. Feed, ingredient and environmental swab samples were analyzed similar to previous work using PEDV.


To date, over 2,000 samples have been collected. Of all samples collected, 17 have been polymerase chain reaction-positive representing 0.8% of all samples. To further characterize where these areas of contamination have been identified, we will first discuss feed trucks.


Unlike much of the feed manufactured and distributed in the U.S. swine industry, the majority of the feed that is produced through the feed mill evaluated is bagged. Thus, bags of feed are loaded at the feedmill onto trucks by hand, and unloaded manually on-farm. In the initial 45 days of the investigation, 370 samples were collected from feed trucks resulting in seven PCR-positives representing both interior and exterior surfaces.


As a result of this, the disinfection procedures for the exterior surfaces of feed trucks was modified and a disinfection procedure was also implemented to address any potential contamination within the cabs of feed trucks. Employee training and emphasis on reducing personnel movement out of the vehicles on farm was incorporated, which likely contributed to reduced detection of contamination of these surfaces as the sampling process continued.


Since these changes have been incorporated, nearly 600 additional samples have been collected from interior and exterior truck surfaces with no additional evidence of ASFV contamination.


In addition to feed delivery vehicles, a number of surfaces within the feed mill have been evaluated totaling 1,040 samples. Of these samples, nine have been identified as PCR-positive for ASFV with three being on exterior surfaces of equipment, three being on interior surfaces of equipment, two on worker clothing and one in an area where feed truck drivers aggregate upon arrival back at the feed mill.


Of the 142 ingredient and finished-feed samples collected and analyzed, only one complete feed sample has tested positive for ASFV.


To further understand these observations, a study was recently conducted at Kansas State University under biosafety level 3Ag conditions...