The survival of several viruses in feed and feed ingredients for prolonged periods has been demonstrated. Feed and feed ingredients have also been investigated as sources of pathogen introduction to farms and as a potential source of infection to animals post consumption of contaminated feed. In a study led by Leonardo C. Caserta, Cornell University, and funded by the Swine Health Information Center (SHIC), researchers determined the rate of decay of Senecavirus A (SVA) in swine feed ingredients as a function of time and temperature and established half-life estimates for the virus. Study findings demonstrate that feed matrices are able to extend the survival of SVA, protecting the virus from decay. Additionally, it was demonstrated that consumption of contaminated feed can lead to productive SVA infection.
Select feed ingredients were spiked with a constant amount of SVA (105 median tissue culture infectious dose 50) and incubated at 4, 15, and 30◦C for up to 91 days. Virus viability and the presence of viral RNA were assessed in samples collected over time. At the three different temperatures investigated, dried distillers’ grains with solubles (DDGS) and soybean meal (SBM) provided the most stable matrices for SVA, resulting in half-lives of 25.6 and 9.8 days, respectively. At 30◦C, SVA was completely inactivated in all feed ingredients and in the control sample, which did not contain a feed matrix. Although virus infectivity was lost, viral RNA remained stable and at consistent levels throughout the experimental period.
Additionally, the ability of SVA to infect swine via ingestion of contaminated feed was investigated in 3-week-old, weaned pigs. Animals were provided complete feed spiked with three concentrations of SVA (105, 106, and 107 per 200 g of feed) and allowed to naturally consume the contaminated feed. This procedure was repeated for three consecutive days. Infection of pigs through consumption of contaminated feed was confirmed by virus neutralization assay and the detection of SVA in serum, feces and in the tonsil of exposed animals by real-time reverse transcriptase PCR.
SHIC, launched by the National Pork Board in 2015 solely with Pork Checkoff funding, continues to focus efforts on prevention, preparedness, and response to novel and emerging swine disease for the benefit of US swine health. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. SHIC is funded by America’s pork producers to fulfill its mission to protect and enhance the health of the US swine herd. For more information, visit http://www.swinehealth.org or contact Dr. Sundberg at [email protected].