Rethinking the uncertainty of African swine fever virus contamination in feed ingredients and risk of introduction into the United States

Abstract

Economically relevant pathogens, such as African swine fever virus (ASFV), have been shown to survive when experimentally inoculated in some feed ingredients under the environmental conditions in transoceanic transport models. However, these models did not characterize the likelihood of virus survival under various time and temperature processes that feed ingredients undergo before they are added to swine diets.Here, we developed a quantitative risk assessment model to estimate the probability that one or more corn or soybean meal ocean vessels (25,000 tonnes) contaminated with ASFV would be imported into the United States annually. This final probability estimate was conditionally based on five likelihoods: the probability of initial ASFV contamination (p0), ASFV inactivation during processing (p1) and transport (p2), recontamination (pR), and ASFV inactivation while awaiting customs clearance at United States entry (p3). The probability of ASFV inactivation was modelled using corn and soybean (extruded or solvent extracted) processing conditions (times and temperatures), D-values (time to reduce 90% or 1-log) estimated from studies of ASFV thermal inactivation in pork serum (p1), and survival in feed ingredients during transoceanic transport (p2 and p3). 'What-if' scenarios using deterministic values for p0 and pR (1%, 10%, 25%, 50%, 75%, and 100%) were used to explore their impact on risk. The model estimated complete inactivation of ASFV after extrusion or solvent extraction processes regardless of the initial ASFV contamination probability assumed. The value of recontamination (ranging from 1% to 75%) was highly influential on the risk of one ASFV-contaminated soybean meal vessel entering the United States. Median risk estimates ranged from 0.064% [0.006%-0.60%; 95% probability interval (PI)], assuming a pR of 1.0%, up to 4.67% (0.45%-36.50% 95% PI) assuming a pR of 75.0%. This means that at least one vessel with ASFV-contaminated soybean meal would be imported once every 1563-21 years, respectively. When all raw corn was assumed to be contaminated (p0 = 100%), and no recontamination was assumed to occur (pR = 0%), the median probability of one vessel with ASFV-contaminated corn entering the United States was 2.02% (0.28%-9.43% 95% PI) or once every 50 years. Values of recontamination between 1% and 75% did not substantially change the risk of corn. Days

Developing a gateway program for importing non‐animal origin ingredients from regions with African swine fever virus

“…While Schambow et al. ( 2022 ) developed a model to predict ASFV entry more accurately through non‐animal origin feed ingredients. Innovative steps such as these can take the place of government regulations and can instead demonstrate the unity and forward thinking of the swine industry.…”

Thermal inactivation of African swine fever virus in feed ingredients

“…As far as we are aware, this is the first report of the thermal inactivation of ASFV in animal and non-animal origin feed ingredients. The heat resistance in terms of D 60 , D 70 , D 80 , and D 85 fulfilled the need of the D T of ASFV in feed ingredients, particularly to estimate the probability of at least one ASFV-contaminated vessel of feed ingredients entering an importing country 12 . Such probability is part of the quantitative risk assessment model developed to evaluate the risk of ASFV entry into ASFV-free countries through imported feed ingredients.…”

“…Medium-chain fatty acid and formaldehyde-based feed additives served as a chemical additive to reduce the ASFV infectivity and the risk of ASFV transmission through feed ingredients 11 . A previous study developed a quantitative risk assessment to evaluate the probability of importing corn or soybean meal on ocean vessels contaminated with ASFV 12 . The D T of ASFV from the thermal inactivation of corn and soybean meal was assumed from that of ASFV in pork serum 12 .…”

“…A previous study developed a quantitative risk assessment to evaluate the probability of importing corn or soybean meal on ocean vessels contaminated with ASFV 12 . The D T of ASFV from the thermal inactivation of corn and soybean meal was assumed from that of ASFV in pork serum 12 . Additionally, the effective thermal inactivation of ASFV at 56 °C for 70 min or 60 °C for 20 min was not specific to the feed ingredient 1 .…”

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

“…Finally, the Special Issue explores the North American response to the risk of infection associated with feed, beginning with the initial attempt to quantify the risk of ASFV introduction to the United States through feed (Schambow et al, 2021), followed by a review of Canada's national approach to manage the risk of ASFV-entry through plantbased feed ingredients (Calvin et al, 2021). The Special Issue closes with a comprehensive review of the collaborations within this new area of science, a description of progress made and obstacles encountered, as the topic of feed risk was introduced and advanced across agriculture, followed by a discussion of the challenges of the risk of feed to the US swine industry: past, present and future (Becton et al, 2021).…”