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

Abstract

Transmission of biological hazards capable of causing disease in livestock can occur through a wide variety of direct and indirect routes. In swine production, there are a large number of possible routes of exposure of a pathogen into a susceptible population. African swine fever virus (ASFV) has been a significant challenge for Southeast Asia since first detected in China in 2018 and has spread through many countries within the region. In order to understand potential transmission pathways within an ASFV endemic region, a diagnostic investigation was performed to determine the level of contamination on a wide variety of surface types within a live animal production, feed manufacturing, and feed distribution system located in Vietnam. All diagnostic testing was performed locally by the production system's internal diagnostic laboratory using real-time polymerase chain reaction (rt-PCR) analysis. Early in the diagnostic investigation, it became clear that feed trucks were a common site of ASFV surface contamination detection. This information resulted in biosecurity-focused actions for feed trucks arriving back at the feed mill, including decontamination of interior truck cab surfaces and washing of exterior truck surfaces with high-pressure water prior to application of surface disinfectants. Additionally, a low number of rt-PCR positive samples were detected within the feed production system, with the greatest number coming from transient surfaces such as high traffic areas and worker clothing. This illustrates the importance of managing employee traffic through procedures such as zoning and separation between clean-dirty areas to reduce the likelihood of pathogen transmission. In conclusion, this report illustrates the importance of routine data capture regarding efficacy of biosecurity procedures which allows for real-time updates and improvement as biosecurity gaps are identified.

Modelling and assessing additional transmission routes for porcine reproductive and respiratory syndrome virus: vehicle movements and feed ingredients

“…Despite the concerns about feed as a route of PRRSV transmission, many uncertainties remain, including the minimal infection dosage required to cause disease, the effectiveness of feed processing such as pelleting, extruding, and roasting and the use of feed additives (Dee et al, 2020; Niederwerder, 2021). In addition, it is important to mention that feed contamination may also occur within the feed mill facility either by contaminated environments, personnel, equipment, birds, or rodents, or even contaminated trailers coming in and out feed mill facilities (Dee et al, 2020; Gebhardt et al, 2021; Niederwerder, 2021), our model does not explicitly consider such uncertainties nor attempt to account for such complexity. In this study we assumed that all feed meals with any amount of animal by-products were still able to cause infection once delivered.…”

“…Despite the promising results, the study did not fully consider indirect contacts through between-farm transportation vehicles (e.g. vehicles transporting pigs, feed or farm personnel) contact networks, which has been previously described as one of the major modes of between-farm transmission of diseases in swine (Büttner and Krieter, 2020; Porphyre et al, 2020; Niederwerder, 2021), such as PRRS (Dee et al, 2002, 2004; Pitkin et al, 2009; Thakur, Sanchez et al, 2015) and African swine fever (ASF) (Gao et al, 2021; Gebhardt et al, 2021).…”

“…In addition, dry conditions, low pH ranging between 5 and 7 (Benfield et al, 1992), iodine, quaternary ammonium or chlorine compounds used in vehicle disinfection were successful in inactivating PRRSV (Shirai et al, 2000). Thus, if environmental conditions favor PRRSV survivability and the vehicles are poorly cleaned and disinfected, the potential for pathogens to disseminate within highly connected networks could indeed play a major role in disease spread (Büttner and Krieter, 2020; Gebhardt et al, 2021).…”

“…In addition to transportation movements, contaminated feed could represent a possible route for pathogen transmission (Gebhardt et al, 2021; Niederwerder, 2021), but the probability of PRRSV transmission through feed has been described as relatively low (Cochrane et al, 2017; Ochoa et al, 2018; Blázquez et al, 2020). However, a recent report by Dee et al 2020, demonstrated under experimental conditions that pigs which consumed pellet feed contaminated with 1×10 5 TCID50/ml of PRRSV became infected.…”

Feed: A new pathway for the domestic and transboundary spread of viral pathogens of veterinary significance

“…These topics are timely, as ASFV DNA has been detected in commercial feed systems in Asia, with a range of 0.5-2.0% of samples collected from dust from complete feed and grain-based ingredients, such as soybean meal, testing positive by PCR. Extending the concept of ASFV risk in feed, this Special Issue describes the complexities of ASFV contamination of the feed milling environment, including an evaluation of feed dust sampling for the detection of the virus at the level of the feeder (Khanal et al, 2021), the feed mill and the swine production facility (Gebhardt et al, 2021). This Special Issue also covers the field of feed risk mitigation, studying the effect of mixing and feed batch sequencing on the distribution of ASFV in feed batches (Elijah et al, 2021), and an evaluation of a novel monoglyceride feed additive designed to reduce the risk of the original viral nemesis in feed, PEDV (Phillips et al, 2021).…”