African swine fever virus is transmissible through animal consumption of contaminated feed. To determine virus survival during transoceanic shipping, we calculated the half-life of the virus in 9 feed ingredients exposed to 30-day shipment conditions. Half-lives ranged from 9.6 to 14.2 days, indicating that the feed matrix environment promotes virus stability.

African swine fever virus (ASFV) is the most significant threat to pork production worldwide. Over the past year, the virus has emerged in new countries and continents, including Belgium (1), and has rapidly disseminated throughout China and several other countries in Asia (2,3). Without effective vaccines or treatment, infection with ASFV results in severe disease in swine, high mortality rates, and preventive culling to halt virus spread. Since the 2013 introduction of porcine epidemic diarrhea virus in the United States, feed and feed ingredients have been recognized as potential routes for transboundary spread of swine diseases (4). Recent work has demonstrated that the stability of ASFV strain Georgia 2007 across animal feed ingredients is broad and that the virus survives in ingredients subjected to environmental conditions mimicking trans-Atlantic shipment (5). Furthermore, experimental infection with ASFV Georgia 2007 can occur through the natural consumption of contaminated plant-based feed; the likelihood of infection increases after repeated consumption of a batch of feed (6). Field reports have also implicated contaminated feed as playing a role in the introduction and transmission of ASFV on farms in China and Latvia (79).

We previously evaluated the stability of ASFV in various feed ingredients during a simulated 30-day trans-Atlantic voyage. We used those data to prepare rough estimates for the half-life of ASFV in each ingredient (5,10). However, half-life calculations were based on the limited data available at the time, including 2 time points representing inoculation dose and titers at the conclusion of the study and insufficient replicates from which to calculate SEs or 95% CIs around the half-life estimates. For this study, our objective was to improve the accuracy of ASFV half-life estimates by increasing the number of time points and replicates in the same trans-Atlantic model.

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Citation:  Stoian A, Zimmerman J, Ji J, et al. Half-Life of African Swine Fever Virus in Shipped Feed. Emerging Infectious Diseases. 2019;25(12):2261-2263. doi:10.3201/eid2512.191002.