Viral Viability and Infectivity in Contaminated Feed and Opportunities for Feed Additives to Mitigate the Challenge

The link between diet and disease transmission has raised concerns that U.S. herds could become infected with foreign pathogens through contaminated feed and feed ingredients originating from countries with endemic disease and lax sanitation and quality assurance procedures. Experimental data has already demonstrated that some feed ingredients, particularly soy-based products, can support the viability of at least three significant viral pathogens of swine (i.e., Classical Swine Fever or CSF, ASF, and PRV) (Dee and others, 2018, Niederwerder and others, 2019). ASF survival has been successfully confirmed in a total of 9 distinct feed ingredients, including three soy-based products, choline chloride, three pet diets, pork sausage casings, and complete feed exported from China to the U.S. (Dee et al., 2018). Two key variables that influence the viability of viruses in feed include the specific virus’s phenotypic properties and the feed matrix that is produced by specific feed ingredients and additives. Some matrices are more conducive to survival and can support several different viruses at the same time.

This discovery had added significance in 2018, when ASF was first isolated in Chinese swine herds. As the US imports soy-based products from several ASFV-positive countries, it becomes important to quantity the amount and type of these products that enter the US and to identify at what seaports does this importation occur. Specifically, the type and quantity of soy-based feed ingredients and specific ports of entry (POE) was evaluated during 2018 and 2019 using data from the International Trade Commission Harmonized Tariff Schedule website. In 2018, 104,707 metric tons (MT) of soy-based ingredients (soybeans, soybean meal, soy oil cake and soy oil) were imported to the US with 52.6 % (55,101 MT) originating from China and 42.9% (44,775 MT) originating from the Ukraine. In 2019, 73,331 MT entered the US with 54.7% (40,143 MT) originating from the Ukraine and 8.4% (6182 MT) coming from China. Regarding POEs, approximately 81% of soy-based imports from China entered the US at San Francisco/Oakland, CA (60.36%) and Seattle, WA (20.54%), while 89.4-100% entered from the Ukraine at New Orleans, LA and Charlotte, NC. The approach allows for the identification and quantification of potential channels of foreign disease entry to the US and allows for the focusing of mitigation efforts and resources at high-risk points (Patterson et al, 2020).

Contaminated feed and feed ingredients are now widely recognized as likely vehicles for the transport and transmission of viral pathogens, highlighting the need for improved biosecurity policies and procedures for imported products intended for use in animal diets. In Canada, restrictions are placed on feed ingredients imported from countries known to be positive for ASF virus that are known to enhance the survival of pathogens, predominantly soy-based products. The Canadian Food Inspection Agency has also established secondary control zones around all national seaports where these high-risk ingredients are received. After arrival, products must be stored under controlled environmental conditions for a specified interval to all adequate time for viral decay prior to distribution to milling facilities. Similar programs have been implemented in Australia and the European Food Safety Authority recently released their scientific opinion that the risk of ASFV movement between countries via feed is “low but cannot be ignored”. In their evaluation, the risk of feed was ranked as a higher risk than transport vehicles returning from ASFV-positive countries as well as blood products and bedding.

New Knowledge This discovery had added significance in 2018, when ASF was first isolated in Chinese swine herds. As the US imports soy-based products from several ASFV-positive countries, it becomes important to quantity the amount and type of these products that enter the US and to identify at what seaports does this importation occur. Specifically, the type and quantity of soy-based feed ingredients and specific ports of entry (POE) was evaluated during 2018 and 2019 using data from the International Trade Commission Harmonized Tariff Schedule website. In 2018, 104,707 metric tons (MT) of soy-based ingredients (soybeans, soybean meal, soy oil cake and soy oil) were imported to the US with 52.6 % (55,101 MT) originating from China and 42.9% (44,775 MT) originating from the Ukraine. In 2019, 73,331 MT entered the US with 54.7% (40,143 MT) originating from the Ukraine and 8.4% (6182 MT) coming from China. Regarding POEs, approximately 81% of soy-based imports from China entered the US at San Francisco/Oakland, CA (60.36%) and Seattle, WA (20.54%), while 89.4-100% entered from the Ukraine at New Orleans, LA and Charlotte, NC. The approach allows for the identification and quantification of potential channels of foreign disease entry to the US and allows for the focusing of mitigation efforts and resources at high-risk points (Patterson et al, 2020). Industry Actions Contaminated feed and feed ingredients are now widely recognized as likely vehicles for the transport and transmission of viral pathogens, highlighting the need for improved biosecurity policies and procedures for imported products intended for use in animal diets. In Canada, restrictions are placed on feed ingredients imported from countries known to be positive for ASF virus that are known to enhance the survival of pathogens, predominantly soy-based products. The Canadian Food Inspection Agency has also established secondary control zones around all national seaports where these high-risk ingredients are received. After arrival, products must be stored under controlled environmental conditions for a specified interval to all adequate time for viral decay prior to distribution to milling facilities. Similar programs have been implemented in Australia and the European Food Safety Authority recently released their scientific opinion that the risk of ASFV movement between countries via feed is “low but cannot be ignored”. In their evaluation, the risk of feed was ranked as a higher risk than transport vehicles returning from ASFV-positive countries as well as blood products and bedding.

Expanding knowledge on the half-lives of viruses found in essential animal feed ingredients has led to science-based protocols in the U.S., which allow these materials to be safely introduced from high-risk countries. This approach is referred to as “Responsible Imports” and relies on a comprehensive risk assessment process that considers: 1) the absolute necessity of importing the material(s); 2) the availability of alternative ingredients that can be obtained through other sources (i.e., countries free of foreign diseases of concern); 3) prevalence of specific virus(es) regarded as credible threats; 4) access to reliable data that describes the half-lives of these agents in designated ingredients and their substrates; 5) projected transport times of feed substrates, from source to end destination; 6) mitigation methods and strategies that can be implemented to reduce viral load during transit; and 7) optimal storage temperatures and times that will eliminate residual virus from various ingredients after receipt and prior to use. The relatively new concept of “feed quarantine” is rapidly evolving, as production companies design storage facilities to safely accommodate incoming products and facilitate secure, long-term trade with a wider range of international partners. (Patterson et al., 2019)

In contrast to the rapid industry-based response to the PEDV epidemic, the risk of feed was immediately downplayed by US governmental agencies, resulting in criticism by the Government Accountability Office (GAO). In their report, the GAO found fault with USDA’s lack of response to the outbreaks in 2013 and 2014, and for insufficient actions taken afterward to prevent future outbreaks. In addition, it stated that the government is not fully prepared to track and respond to emerging diseases that could harm animal health, decrease availability of food, and increase food prices. Unfortunately, despite the growing body of scientific evidence in support of the risk as it pertains to other pathogens, the risk of feed ingredients continues to be ignored, thereby continuing to expose US agriculture to the risk of the introduction of foreign animal diseases via contaminated feed ingredients.

Currently, all parties continue to work together to reach consensus. Research on feed risk mitigation is ongoing and results are being communicated between all parties. Industry stakeholder groups and federal agencies continue to interact via a national task force, focusing on the risk of foreign animal disease entry through contaminated feed. In the end, it is hoped that these efforts will stimulate communication and collaboration between the feed and livestock industries, and governmental agencies, furthering the emerging concept of “global feed biosecurity”.