Senecavirus A in the environment of sow slaughter plants

Authors: HOFFMAN, KYLE - Orise Fellow; HUMPHREY, NICKI - Animal And Plant Health Inspection Service (APHIS); KORSLUND, JOHN - Animal And Plant Health Inspection Service (APHIS); Faaberg, Kay; Lager, Kelly; Buckley, Alexandra

Submitted to: Conference Research Workers Disease Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/20/2021
Publication Date: 12/6/2022
Citation: Hoffman, K., Humphrey, N., Korslund, J., Faaberg, K.S., Lager, K.M., Devries, A.C. 2022. Senecavirus A in the environment of sow slaughter plants. Conference Research Workers Disease Meeting. 2022 Jun 22;9:923878. https://doi.org/10.3389/fvets.2022.923878.
DOI: https://doi.org/10.3389/fvets.2022.923878

Interpretive Summary:

Technical Abstract: Introduction Vesicular disease caused by Senecavirus A (SVA) is clinically indistinguishable from other vesicular diseases of swine. A foreign animal disease investigation (FADI) is required every time a vesicular lesion is observed. Since 2015 there has been an increase in the number of FADIs and SVA positive samples at slaughter plants in the U.S. The objectives of this study were to: 1) understand the environmental burden of SVA in select sow slaughter plants, 2) correlate PCR, VI and swine bioassay results, and 3) sequence 2020 SVA isolates for comparison to previously sequenced SVA isolates. Materials and Methods Environmental swabs were collected from four sow slaughter plants (Plants 1-4) from June to December 2020. All swab samples were tested for SVA by PCR and virus isolation (VI). Eighteen samples of various Ct values were selected to inoculate individually housed pigs (n=2/sample). Fecal and oral swabs and serum samples were tested for SVA by PCR to determine infectivity to swine. Finally, two isolates from Plants 1-3 (n=6 total) were selected for next-generation sequencing and analysis. Results SVA PCR positive samples were consistently found at Plants 1-3, while Plant 4 had no positive samples. The greatest percentage of SVA positive samples was found in the summer and peaked in August. Among 450 samples taken from Plants 1-3, 308 samples were PCR positive. Of the samples with a Ct value below 30, 76.5% were VI positive, while only 11.2% of samples with a Ct value greater than 32 were VI positive. Samples for the swine bioassay had Ct values ranging from 24 to 33 and only one sample (Ct value = 24) infected pigs and had detectable nucleic acid in samples collected. Genome sequences of the 2020 isolates generally clustered together and with other contemporary US isolates. Conclusion The work in this study demonstrated that SVA is in the environment of sow slaughter plants, but the virus detected may be unlikely to infect to swine. A better understanding of the epidemiology of SVA in the marketing chain may help reduce the number of FADIs and aide in the development of control measures to reduce the spread of SVA.