and environmental conditions simulating shipment from Warsaw, Poland to the port of LeHarve, France, to the port of New York City, NY, US and then to Des Moines, IA, US. [17] Under the conditions of this study, SVA (representing FMDV), FCV (representing VESV), BHV-1 (representing PRV), PRRSV, PSV (representing SVDV), ASFV and PCV2 maintained infectivity, while BVDV (representing CSFV), VSV, CDV (representing NiV) and IAV-S did not. As before, the majority of viruses survived in conventional soybean meal, lysine hydrochloride, choline chloride, vitamin D and pork sausage casings. These collective results led to the development of the concept of “high-risk combination” (the right virus in the right ingredient) and contributed to the growing body of evidence that contaminated feed ingredients may represent a risk for the transport of pathogens at domestic and global levels.


“The world’s worst pig virus enters the world’s biggest pig farm”, GD Spronk DVM These findings became significant following the announcement of the initial cases of ASFV in China’s pig population during August, 2018 for several reasons: 1. Fifty percent of the world’s pigs were in China at the time. 2. The Chinese national herd was naïve to ASFV. 3. ASFV survived in nine of 12 of the ingredients utilized in the study, including three varieties of soy-based products, choline chloride, three types of pet food, pork sausage casings and complete feed [17]. 4. The US imported approximately 2 M metric tons of agricultural products, including 55,000 metric tons of soy-based products from China, along with 45,000 metric tons and 3,000 metric tons of soy-based products from the Ukraine and Russia, respectively, in 2018 [18].


This crisis accelerated the research efforts to better understand


the risk of feed, specifically as it pertained to ASFV. This resulted in the seminal work of Niederwerder et al., who documented transmission of ASFV to naïve pigs following natural consumption of contaminated feed and water [19]. This study determined the minimum infectious dose of ASFV in liquid (101 TCID50) and in feed (104 TCID50) following a one-time exposure. However, further analysis indicated that the more frequent the exposure (3x, 10x, 30x) to virus in feed or water, the higher the probability of infection, even in the presence of lower doses (102 TCID50). Another significant finding was the calculation of ASFV half-life in feed ingredients. Original estimates, based on limited (n =2) data points derived from the trans-Atlantic model indicated that half-life ranged from 4-5 days across all nine of the virus-positive ingredients [17]. Niederwerder again used the Trans-Atlantic model to conduct a more comprehensive half-life evaluation, incorporating data from all four sampling points in the model, resulting in half-live values that ranged from 9.6-14.2 days (inclusive of 95% confidence intervals) across all nine supportive ingredients [20], suggesting that ASFV survival could occur far beyond the 30-day transport period used in the model. In conclusion, there appears is a growing body of experimental


evidence that specific viral agents in combination with the proper ingredient can survive long-distance transport under simulated transboundary conditions. It is now clear that pathogens such as PEDV and ASFV can be transmitted through feed, and the minimum oral infectious doses have been calculated. Furthermore, additional work has documented survival of both PRV and CSFV throughout the Trans- Pacific model in feed ingredients [21], bringing up the need to address the management of this novel risk factor.


PART 2: WHAT DO WE DO? Since the discovery of PEDV in the US and the role that feed appears to play in the epidemiology of the disease, there has been extensive effort put forth to evaluate the efficacy of multiple protocols and products to reduce risk. Reviewing the literature, current publications have centered on one of four approaches: mechanical reduction (flushing and sequencing of feed batches), heat treatment, chemical mitigation and/ or storage time of feed prior to feeding. As a complement to this work, a validated sampling method has been developed [22]. A recent publication by Jones et al indicated that the sampling of bulk ingredients for PEDV should include compositing at least 10 individual samples and that the ability to detect is dependent upon dose and loss of viral load (~10 Ct) during the extraction methods involving feed samples can be expected [22]. While more work is needed, this is a good first step to not only conduct surveillance and measure the risk of potentially contaminated feed, but to validate the efficacy of mitigation protocols as well.


Strategy 1: Mechanical reduction (flushing and sequencing) Several experiments have been conducted to assess the efficacy of decontaminating feed and feed manufacturing facilities through the physical process of mixing, using repeated sequencing of clean feed following known contaminated batches or through the use of chemically treated rice hulls [23,24]. In regards to sequencing, results demonstrated that sequenced batches of feed had reduced quantities of PEDV RNA, although sequenced feed without detectible PEDV RNA was still infectious [23]. Therefore, this protocol can reduce but not eliminate the risk of producing infectious PEDV carryover from the first batch of feed. In regards to the use of chemically treated rice hulls, flushes treated with formaldehyde or medium chain fatty acid blends reduced the quantity of detectible RNA present after mixing a batch of PEDV- positive feed [24].


Strategy 2: Heat treatment Several studies have demonstrated a positive effect of temperature on the survival of PEDV in feed [25-28]. Early work on the effect of heat-treatment by Trudeau et al indicated that heating swine feed at temperatures over 130°C effectively reduced PEDV survival [24,25]. Furthermore, the spray drying process also was effective in inactivating infectious PEDV in plasma protein [27]. Finally, in regards to pelleting, conditioning and pelleting temperatures above 54.4°C were effective in reducing the quantity and infectivity of PEDV in swine feed [28]. In contrast, viable virus was present following exposure to lower (37.80C and 46.1°C) conditioning temperatures.


Strategy 3: Chemical mitigation Extensive studies has been conducted to evaluate the effect of chemical mitigation on PEDV-contaminated feed. The initial work revolved around a product called Sal CURB®


(Kemin Industries, Des Moines, IA,


USA), an FDA-approved liquid antimicrobial used to control Salmonella contamination in poultry and swine diets. In groups of pigs fed Sal CURB®


-treated feed spiked with PEDV versus non-treated feed, clinical


signs of PEDV infection (vomiting and diarrhea) and viral shedding in feces were observed 2-3 days post-consumption of non-treated feed. In contrast, no evidence of infection was observed in pigs fed Sal CURB®


-treated feed [29]. In another study, feed samples were spiked


with PEDV and mixed with either organic acid mixtures, sugar, or salt was incubated at room temperature for up to 21 days. All additives


FEED COMPOUNDER NOVEMBER/DECEMBER 2019 PAGE 59


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68