Survival of porcine coronaviruses in feed ingredients and impact of feed additives

A lot of research has been done at the University of Minnesota regarding the survival of porcine coronaviruses in the feed and how to impact their survival. We are presenting today two papers published this spring looking at this important topic. First, Trudeau et al. showed that the feed ingredient which lead to the longest porcine coronaviruses’ survivability was soybean meal. Then, Cottingim et al. showed that some feed additives could inactivate PDCoV.

Importance of porcine coronaviruses and their relationship to swine feed

Porcine coronaviruses of importance in the swine industry nowadays are Porcine Epidemic Diarrhea virus (PEDV), Transmissible Gastroentiritis virus (TGEV), and Porcine Delta Coronavirus (PDCoV). All cause enteric issues in swine and some can lead to up to 100% mortality in nursing piglets. The role of feed ingredients in spreading PEDV and causing outbreaks in Northern America in 2013 has been questioned since then.

Survival of PEDV, TGEV, and PDCoV in complete feed and feed ingredients

The first research project evaluated the persistence of PEDV, TGEV, and PDCoV in porcine feed and feed ingredients. To do so, complete feed and major feed ingredients samples (spray dried porcine plasma, meat meal, meat and bone meal, blood meal, corn,
soybean meal, and corn dried distillers grains with solubles) where inoculated with PEDV, TGEV, or PDCoV and kept for up to 56 days. Aliquots were tested 11 times between the inoculation day and the end of the trial. Time necessary to reduce the viral concentration by 1 log was recorded.

Soybean meal took the longest time to attain the reduction in concentration for all of the coronaviruses, reaching 7.5 days for PEDV, and 42 days for both PDCoV and TGEV. This study also demonstrated that there was a modest positive correlation between moisture content and persistence of TGEV and PDCoV. On the other end, there was a moderate negative correlation between ether extract content and TGEV survival, not observed with the other two viruses.

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Trudeau coronavirus feed swine survival PED

Feed additives and PDCoV survival

In this second project, the survival of PDCoV was evaluated after being put in contact with nursery feed samples containing one of six different commercial feed acids (UltraAcid P, Activate DA, KEMGEST, Acid Booster, Luprosil, and Amasil), salt, or sugar. Acids were added following the recommended concentrations in the first part of the experiment and then, were double-dosed. Feed samples were inoculated with PDCoV and kept for up to 35 days. Like in the previous article, days to achieve a reduction of virus concentration by 1 log were recorded.

At recommended values, there was no difference between viral load reduction in feed samples with or without additives. When acids were added to the feed at a double concentration, the time period to attain the reduction in viral load was decreased to 0.28 days or less for all acids except for Amasil which increased it to 4.95 days (control: 0.35 days). The difference between acidifiers may be explained by the active ingredients used in the products. Furthermore, the addition of salt decreased PDCoV survival whereas sugar increased it.

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Cottingim feed additives survival PDCoV coronavirus swine

 

Can biosecurity measures prevent PEDV transmission?

Summary:

Porcine Epidemic Diarrhea virus is highly contagious.

The 2013 Porcine Epidemic Diarrhea virus’ (PEDV) outbreak in the USA taught the swine industry that the virus is highly contagious. This event forced producers and veterinarians to review and upgrade their biosecurity procedures.

Drs. Torremorell, Cheeran, and Goyal from the University of Minnesota evaluated some of these measures and how they can prevent PEDV transmission.

Changing Personal Protective Equipment (PPE) and showering before entering a new room prevented contamination.

Among the measures included in this study were the use and change of PPE as well as showering in and out of a facility. In the low biosecurity setting, personnel went from a room with PEDV positive pig straight to a room with naive pigs, contaminating them after the very first movement. In the medium biosecurity setting, personnel washed their hands and face and change their PPE before being in contact with the naive pigs. In this situation, pigs stayed negative for PEDV but  two personnel hair/face swabs came back positive for viral genetic material. On the contrary, personnel showered before getting in contact with the high biosecurity group. Those pigs as well as all personnel tests remained negative for PEDV during the study.

 

Torremorell PEDV biosecurity 2017

Abstract

Background:

The effectiveness of biosecurity methods to mitigate the transmission of porcine epidemic diarrhea virus (PEDV) via farm personnel or contaminated fomites is poorly understood. This study was undertaken to evaluate the effectiveness of biosecurity procedures directed at minimizing transmission via personnel following different biosecurity protocols using a controlled experimental setting.

Results:
PEDV RNA was detected from rectal swabs of experimentally infected (INF) and sentinel pigs by real-time reverse transcription polymerase chain reactio n (rRT-PCR). Virus shedding in INF pigs peaked at 1 day post infection (dpi) and viral RNA levels remained elevated through 19 dpi. Sentinel pigs in the low biosecurity group (LB) became PEDV positive after the first movement of study personnel from the INF group. However, rectal swabs from pigs in the medium biosecurity (MB) and high biosecurity (HB) groups were negative during the 10 consecutive days of movements and remained negative through 24 days post movement (dpm) when the first trial was terminated. Viral RNA was detected at 1 dpm through 3 dpm from the personal protective equipment (PPE) of LB personnel. In addition, at 1 dpm, 2 hair/face swabs from MB personnel were positive; however, transmission of virus was not detected. All swabs of fomite from the HB study personnel were negative.
Conclusions:
These results indicate that indirect PEDV transmission through contaminated PPE occurs rapidly (within 24 h) under modeled conditions. Biosecurity procedures such as changing PPE, washing expose d skin areas, or taking a shower are recommended for pig production systems and appear to be an effective option for lowering the risk of PEDV transmission between groups of pigs.

Link to the full text

Air samples successful in detecting on-farm PRRSV, PEDV, and high-path avian influenza virus