New Study Explores the Risk and Mitigation of Foot-and-Mouth Disease Virus in Feed

Introducing important work examining the role of contaminated feed as a vector for transmission of foot-and-mouth disease virus (FMDV), a new study, funded by SHIC, the National Pork Board and ARS/USDA, was published in July 2021.* Specifically, the study performed by researchers from ARS/USDA at Plum Island, evaluated the potential risk of incursion of FMDV into naïve pig herds through contamination of feed. Per the study report, the goal of the project was the assessment of the infectiousness (viability) of FMDV in commercial whole pig feed and pig feed ingredients. Additionally, the researchers, led by Drs. Stenfeldt and Arzt, determined the dose required to infect pigs through natural feeding behavior. Finally, the project looked at the ability of select commercially available feed additives to reduce infectivity of contaminated feed. “While comparable research investigating the potential biosecurity risks of imported feed exists for other viral pig pathogens (Dee et al., 2018; Niederwerder et al., 2020; Niederwerder et al., 2019), this is the first comprehensive evaluation of the risk of FMDV infection of pigs through ingestion of contaminated feed under controlled experimental conditions,” wrote the authors.

In discussion of the study, authors noted many conditions must be met for transmission of viral diseases through pig feed to occur. They also acknowledged that understanding these conditions is critical in order to quantitate the associated risk as well as consider preventative measures. Per their report:

• The feed must first become contaminated with the virus.
• The virus in the feed must then remain viable until it is fed, and the quantity of infectious virus must be sufficient to surpass the minimum infectious dose.
• Finally, at least one pig must consume enough virus to become infected over one or multiple feedings.

In this study, these requirements were considered in the context of pathogen incursion occurring before or during transoceanic transport (Dee et al., 2018). The combined output from the current investigation demonstrated that the likelihood of all of these conditions being met will depend on:

• specific feed ingredient (and any added mitigants)
• strain of the virus
• environmental conditions during storage and transport of the feed

In the conclusion, authors wrote, “The combined output of this investigation demonstrated that FMDV can remain viable as a contaminant of pig feed products through 37 days. In addition to expected variation associated with storage temperature, there was also substantial variability in viability of different FMDV strains in different feed matrices. FMDV exposure by feeding of experimentally contaminated feed to pigs caused FMD with dose dependency. The minimum dose required to cause FMD varied between virus strains and with experimental design and the probability of infection increased when a given dose of virus was divided across three consecutive feedings, likely due to increased exposure time.”

Findings of this work demonstrate:

• FMDV introduction through import of contaminated feed products is plausible
• Addition of additives to feed may mitigate this risk
• Risk of infection varies depending on the contaminated product, the viral strain, and feeding conditions

SHIC, launched in 2015 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 psundberg@swinehealth.org.

* Stenfeldt, C., Bertram,M. R., Meek, H. C.,Hartwig, E. J., Smoliga, G. R., Niederwerder,M. C., Diel, D. G., Dee, S. A., & Arzt, J. (2021). The risk and mitigation of foot-and-mouth disease virus infection of pigs through consumption of contaminated feed. Transboundary and Emerging Diseases, 1–16. https://doi.org/10.1111/tbed.14230