The Canadian Food Inspection Agency (CFIA) released information on 18 February 2014, related to preliminary findings of a bioassay concerning feed or feed ingredients contributing to recent cases of PED in Ontario. Though the CFIA reported the sample of porcine plasma collected at a feed mill infected pigs, the results of the CFIA bioassay do not identify the source of infective virus present in the sample tested.

During a telephone meeting with Ontario Pork Producers, Canada’s Chief Veterinary Officer, Dr Harpreet Kochhar stated: "The results are 'very preliminary' and CFIA is continuing its tests. He speculates there could have been contamination of the plasma after production or “there is some compromise in the plasma production. The plasma in piglet feed is 'sprayed at a very high temperature, which should kill the virus," he notes. (BetterFarming.com)

There are many issues to consider:

1) After years of use around the world, spray-dried plasma has never been identified as a vector of disease

Spray-dried plasma has been commonly used in swine diets for over 30 years. During this time, spray-dried plasma has never been identified as a vector for the spread of any disease. In fact, it is recognized as a feed ingredient that reduces the extent and severity of disease including diarrhea and inflammation associated with many infections. Many controlled studies have confirmed this observation (Dewey et al., 2006; Torrallardona, 2010; Bosi et al., 2004; Coffey and Cromwell, 2001; Van Djik et al., 2001).

Spray-dried porcine plasma imported from the US and Canada has been safely used for many years in swine populations free of swine diseases such as PRRSv (Pileri et al., 2013).

2) Commercially-produced spray-dried plasma has been shown to be a safe feed ingredient

Research has shown that few viruses survive the spray drying process. The PRRSv and Pseudorabies virus (PRv) are envelope viruses inactivated by heat treatment (Polo et al., 2005). In these experiments, plasma was inoculated with either infective PRRSv (Experiment 1) or infective PRv (Experiment 2). In both experiments, it was reported that after spray drying PRRSv and PRv were not infective. Subsequent bioassays confirmed that pigs fed diets with high levels of spray-dried porcine plasma did not become infected with PRRSv, PRv or any other disease (Polo et al., 2005). Spray drying has also been shown to inactivate Swine Vesicular Disease Virus (SVDv), a non-enveloped virus that is more heat stable than most enveloped viruses (Pujols et al., 2007).

Porcine circovirus type 2 (PCV2) is a small, circular, DNA virus highly resistant to heat treatment. Commercially-produced, spray-dried porcine plasma PCR positive for the PCV2 genome fed to naïve pigs did not transmit PCV2 (Shen et al., 2011; Pujols et al., 2008). Furthermore, neutralizing antibodies present in commercially-collected pooled plasma are able to inactivate potential viral contamination (Shen et al., 2011; Polo et al., 2013). Antibody titer in commercially-collected porcine plasma is a reflection of pathogen exposure of the swine population (Borg et al., 2002).

Recent bioassays conducted with spray-dried porcine plasma PCR positive for PEDv genome (Rovira, 2014, personal communication) did not infect pigs with PEDv. Likewise, a number of bioassays testing the infectivity of PCR-positive feeds have failed to result in disease transmission (Rovira, 2013).

Heat treatment has been shown to inactivate PEDv infectivity in swine feces kept on aluminum trays if heated to and held at 160°F (71°C) for 10 minutes or if left at room temperature (68oF or 20°C) for seven days (National Pork Board PED Research Update #13-227). Similarly, PEDv survived in experimentally infected dry feed stored at room temperature (around 24°C) for only one week but not for two, three, four and five weeks (National Pork Board PED Research Update #13-215).

Spray-dried plasma is heated to 176°F (80°C) throughout substance. The dry feed ingredient is eight per cent moisture with a very low water activity (Aw<0.60). Typical storage in dry warehouse conditions can range between four weeks to over one year. Coronaviruses would not be expected to survive such dry conditions over extended periods of time.

Responding to the potential animal health risk of spreading PEDv by blood products to swine, the Department of Environment, Food and Rural Affairs (DEFRA) acknowledged that spray drying is an effective heat treatment for producing a safe feed ingredient (DEFRA, VITT/1200 PED in USA; 24/07/2013 ). Heat treatment of 176°F (80°C) throughout substance of meat and dairy proteins is recognized by the EU to inactivate many viruses including Foot and Mouth Disease, Classical Swine Fever, Swine Vesicular Disease, African Swine Fever, Avian Influenza, Newcastle Disease, Rinderpest, and Sheep and Goat Plague (EU Directive 2002/99/EC, Annex III).

In summary, results of the CFIA bioassay do not indicate the source of infective virus present in the sample tested. The scientific evidence to date indicates that spray-dried plasma is safe. Commercial plasma produced following Good Manufacturing Practices has never been shown to be infective. The potential exists for post-processing contamination of this sample. Consequently NASDBPP is undertaking a thorough investigation into all possible ways this could have occurred. NASDBPP will continue working to understand processing conditions and safety issues related to spray-dried blood products and will fully cooperate with government officials in both the US and Canada in the investigation.

For the references cited, click here.