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According to a new US study, African Swine Fever (ASFv) virus can be easily transmitted orally by water and feed, although the doses needed for infection are higher in animals. herbal foods.
This was the conclusion of research conducted by a team of scientists at Kansas State University. The team, led by Dr. Megan Niederwerder, Assistant Professor of Diagnostic Medicine and Pathobiology, investigated the potential for spread of the APP virus in feed and feed ingredients. The study was published in Emerging Infectious Diseases, a journal published by the US Centers for Disease Control and Prevention (CDC).
Feed and water can be sources of transmission of African swine fever virus. Photo: Henk Riswick
The PPP levels needed in the liquid are very low
Dr. Niederwerder's team found that the level of virus required to cause an infection in a fluid was extremely low, demonstrating the high infectivity of oral PPP. Although higher levels of virus have been required to cause an infection through feed, the high frequency of exposure can make contaminated food a more important risk factor.
In the document abstract, the team explained that they were using an isolated strain in Georgia, Georgia, in 2007, to determine the minimum and median oral and infectious doses of the strain in natural behaviors. consumption and diet.
Probability of PPP infection in animal feed
In a press release published on the KSU website, Dr. Niederwerder explained: "In collaboration with the statistician Trevor Hefley, we were able to model the likelihood of infection with African swine fever when pigs consume lot of food contaminated over time. The likelihood of infection increases dramatically after even 10 exposures or the consumption of 1 kg of contaminated food. Multiple exposure modeling increases the applicability of our experimental data to what would happen on the farm. "
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Dr. Megan Niederwerder, Kansas State University. Photo: KSU
The abstract of the scientific article stated that the minimum infectious dose of ASFv in a liquid was 100 doses to 50% of infections for tissue culture (TCID50), against 104 TCID50 in the Food for animals. The median infectious dose was 101.0 TCID50 for liquids and 106.8 TCID50 for animal feed.
The reason for studying the link between the APP and the diet
In a peer-reviewed article, the team wrote in more detail that some outbreaks in Russia and China were sometimes difficult to explain, prompting them to pursue this particular research: "Molecular characterization of recent incursions of AFSV in China and Siberia demonstrate similarity in viral isolates with ASFv strain Georgia 2007. These outbreaks occurred in herds separated by thousands of kilometers. […]
"In addition, an ASFv incursion has recently been reported in a large scale and high biosecurity farm in Romania. Contaminated Danube water was involved in the introduction of ASF on the 140,000 pig farm.
"Contaminated food as a transmission vector for the introduction of transboundary animal diseases in high biosecurity pork farms is recognized as a major risk factor since the introduction of the swine diarrhea virus to epidemics ( PEDv) in the United States in 2013. The lesson from PEDv highlights the need to quantify the risk posed by animal feed when introducing other transboundary animal diseases. "
Dr. Niederwerder also recently studied the subject of microbiome modulation in pigs – she described this topic in Pig Progress' special report on intestinal health.
Drying of forage crops on roads
In his press release, Dr. Niederwerder described this study as "the first to demonstrate that ASF can be easily transmitted through the natural consumption of contaminated food and fluids". As a result, it is difficult to overstate the relevance of the finding as agricultural processing methods for animal feed ingredients may expose them to a risk of contamination. The press article refers to the current Chinese practice of drying crops on the roads, which could be contaminated by truck traffic containing infected pigs. The treatment of ingredients on contaminated material is another possible source of transmission of viral particles to food.
Dr. Niederwerder explained on the KSU website: "Millions of kg of feed ingredients are imported from countries where the African swine fever virus is currently circulating." virus after exposure to environmental conditions simulating cross-border shipping.
Next steps of FSA research
The next step for the team will be to identify ways to reduce or eliminate this risk, including chemical additives, storage time, heat treatments or others.
Dr Niederwerder said: "African swine fever is probably the biggest threat to global swine production. In the absence of effective vaccine or treatment, the primary goal of disease-free countries is to prevent the introduction of the virus. We hope that this research will further define possible pathways for spreading the disease and develop mitigation strategies to prevent introduction into the US hog herd. "
The peer-reviewed article was written by Megan C. Niederwerder, Ana MM Stoian, RR Rowland Raymond, Steve S. Dritz, Vlad Petrovan, Laura A. Constance, Jordan T. Gebhardt, Matthew Olcha, Cbadandra K. Jones, Jason C. Woodworth, Ying Fang, Jia Liang and Trevor J. Hefley, all affiliated with Kansas State University, Manhattan, KS, USA.
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