COVER STOR ▶▶▶Y Five questions about the
Ever since the introduction of Porcine Epidemic Diarrhoea virus into the United States in 2013, the US has been extra aware of the risk of animal diseases entering through feedstuffs. No wonder that the role of feed gets a major emphasis in US research on African Swine Fever. What role exactly can feed play in transmission and mitigation of the virus?
BY DR MEGAN NIEDERWERDER, DVM, PHD, ASSISTANT PROFESSOR, KANSAS STATE UNIVERSITY, USA*
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wine enteric coronaviruses, including Porcine Epi- demic Diarrhoea virus (PEDv) and porcine delta- coronavirus (PDCoV), are considered the last major transboundary swine diseases introduced into the
US pig herd in 2013 and 2014, respectively. Several epidemiological analyses into the introduction and rapid spread across new farms revealed the potential source of the virus as contaminated feed and feed ingredients. Although there are other risk factors, such as illegally smug- gled pork products, for introduction of ASFv into the US, plant-based feeds and feed ingredients are of particular concern due to several unique characteristics. What are the relevant questions to ask?
Which ingredients support ASFv stability? Identifying which feed ingredients provide an envi- ronmental matrix that supports ASFv stability is an
▶ ALL ABOUT FEED | Volume 29, No. 4, 2021
important step in determining risk. To evaluate this risk us- ing a transboundary shipment model, in 2018 a team of re- searchers led by Dr Scott Dee selected 12 feeds, ingredients or products of animal origin based on import volume and use in swine feed for evaluating ASFv stability. Ingredients included conventional soybean meal, organic soybean meal, soy oilcake, distillers dried grains with sol- ubles (DDGS), lysine, choline, vitamin D, moist cat food, moist dog food, dry dog food, pork sausage casings and complete feed. After 30 days of transatlantic shipment conditions, ASFv Georgia 2007 was broadly stable across diverse ingredients, with infectious virus being detected in 75% of the tested in- gredients, including conventional soybean meal, organic soybean meal, soy oilcake, choline, moist cat food, moist dog food, dry dog food, pork sausage casings and complete feed.
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Is ASFv transmitted through plant-based feed? ASFv transmissibility through the oral route has been appreciated for a century and was recognised
early on as having more variability than parenteral routes of inoculation. However, transmissibility of the modern ASFv Georgia 2007 isolate through natural drinking of contaminat- ed liquid and natural eating of contaminated plant-based feed was only recently characterised. For this study, infectivity rates in nursery pigs were determined at various ASFv doses consumed naturally in small volumes of liquid media (100ml) or complete feed in meal form (100g). Confirmed infection occurred through both drinking and eating routes, with lower doses required for transmission in liquid compared to feed.
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