Evaluating the distribution of African swine fever virus within a feed mill environment following manufacture of inoculated feed

Abstract

It is critical to understand the role feed manufacturing may have regarding potential African swine fever virus (ASFV) transmission, especially given the evidence that feed and/or ingredients may be potential vectors. The objective of the study was to evaluate the distribution of ASFV in a feed mill following manufacture of contaminated feed. To accomplish this, a pilot-scale feed mill consisting of a mixer, bucket elevator, and spouting was constructed in a BSL-3Ag facility. First, a batch of ASFV-free feed was manufactured, followed by a batch of feed that had an ASFV-contaminated ingredient added to feed, which was then mixed and discharged from the equipment. Subsequently, four additional ASFV-free batches of feed were manufactured using the same equipment. Environmental swabs from 18 locations within the BSL-3Ag room were collected after each batch of feed was discharged. The locations of the swabs were categorized into four zones: 1) feed contact surface, 2) non-feed contact surface < 1 meter away from feed, 3) non-feed contact surface > 1 meter from feed, and 4) transient surfaces. Environmental swabs were analyzed using a qPCR specific for the ASFV p72 gene and reported as genomic copy number (CN)/mL of environmental swab processing buffer. Genomic copies were transformed with a log10 function for statistical analysis. There was no evidence of a zone × batch interaction for log10 genomic CN/mL (P = 0.625) or cycle threshold (Ct) value (P = 0.608). Sampling zone impacted the log10 p72 genomic CN/mL (P < 0.0001) and Ct values (P < 0.0001), with a greater amount of viral genome detected on transient surfaces compared to other surfaces (P < 0.05). This study illustrates that once ASFV enters the feed mill environment it becomes widespread and movement of people can significantly contribute to the spread of ASFV in a feed mill environment.

Sampling and detection of African swine fever virus within a feed manufacturing and swine production system

“…Additionally, these data are in agreement with risk assessments put When focusing on environmental samples collected at the feed mill in the current investigation, there were only nine of 1159 samples which contained detectable ASFV DNA (0.78%). Data recently published indicate that when using feed manufacturing equipment in a controlled research setting to mix feed inoculated with ASFV, the virus can be found on a number of different surface types even after multiple subsequent batches of feed are mixed (Elijah et al, 2021) In the current investigation, several key areas of environmental contamination were identified including high-traffic areas and worker clothing. Likewise, the greatest area for contamination within the live animal transfer infrastructure sampled was live animal transport vehicles, specifically the cabs of these vehicles.…”

“…Additionally, the ability to detect viral RNA within the environment can persist for extended periods of time, and can only be removed through intensive cleaning, disinfection, and thermal processing measures (Huss et al., 2017 ). Recently, evidence has been generated that indicates ASFV can become widely distributed within a feed mill when manufacturing inoculated feed in a controlled setting (Elijah et al., 2021 ). Additional research is necessary to further understand these environmental distribution characteristics in a real‐world setting, but initial evidence indicates that environmental sampling for ASFV within a feed manufacturing facility may be a useful diagnostic tool similar to sampling for PEDV.…”

“…When focusing on environmental samples collected at the feed mill in the current investigation, there were only nine of 1159 samples which contained detectable ASFV DNA (0.78%). Data recently published indicate that when using feed manufacturing equipment in a controlled research setting to mix feed inoculated with ASFV, the virus can be found on a number of different surface types even after multiple subsequent batches of feed are mixed (Elijah et al., 2021 ). Within this recent controlled research, the level of detection of ASFV DNA on feed contact, non‐feed contact, and transient surfaces which were researcher boots was greater than what was observed in the current investigation (10%–100% of PCR reactions having detectable ASFV DNA depending on sampling location and batch compared to 0.78% in current investigation).…”

Detection and investigation of atypical porcine pestivirus in a swine production system

“…Environmental sampling using 10 × 10 cm cotton gauze was conducted similar to Elijah et al ( 12 ). Briefly, environmental swabs were taken after the isolation nursery was sanitized but before new pigs were placed at the location.…”

“…Environmental sampling using 10 × 10 cm cotton gauze was conducted similar to Elijah et al (12). Briefly, environmental FIGURE Depiction of the relationship between the isolation nursery barn, the farrow-to-finish site, and o -site finisher barn and timeline of events during this investigation of atypical porcine pestivirus persistence (APPV) in pigs.…”