Iowa State University College of Veterinary Medicine (ISU CVM) and the North American Spray Dried Blood and Plasma Producers (NASDBPP) wish to submit a clarification statement regarding an article published in the December 15, 2009 issue of National Hog Farmer entitled Circovirus Shedding, Transmission, Plasma, Transport Roles Scrutinized.
In the section where plasma is discussed as a potential vector for the spread of PCV2, the research summary did not include the Materials and Methods of the study. This section provides critical information outlining the specifics of the experimental spray dried porcine plasma product used in this study. It is important for the reader to understand the significant differences between commercially produced spray dried porcine plasma and the experimentally produced spray dried porcine plasma product used.
Although the outcome of the research raises concern about the potential for transmission of viruses in spray dried plasma and warrants conducting more research in this area, it is not appropriate to conclude that the experimentally produced plasma product represents commercially produced spray dried porcine plasma.
Some of the differences between experimentally produced product and commercially produced product include, but are not limited to, the source animal(s), pooling effects, processing temperatures, product retention time and post drying conditions. These differences are significant and are outlined in the table below.
| Experimental Plasma | Commercial Plasma (Typical) | Animal Source | Plasma from a single pig infected with PCV2 exhibiting clinical signs of PMWS. High viremia. |
Plasma from pigs inspected by Federal Authorities and passed as fit for slaughter for human consumption. Pigs are ambulatory and free of clinical sign of disease. |
|---|---|---|
| Pooling | No pooling; plasma collected from single clinically ill grower pig. Minimal neutralizing antibody titer. |
Pooled collection from 8,000 – 20,000 healthy, mature market weight pigs. Contains neutralizing antibodies to wide range of pathogens. |
| Inlet temperature (°C ) |
166 | 200 to 240 |
| Outlet temperature (°C) | 67 | 80 to 90 |
| Dwell/Retention time (drying chamber) |
< 1 second | 20 seconds to 1 minute |
| Post drying configuration (cyclone, bag house) | None Immediate cooling to ambient temperature. |
Product collection and conveyance extend the time exposed to heat. Packaged in 25 kg bags or 1 ton totes extending time for dissipation of heat. |
Pooling plasma from healthy source pigs maximizes the potential for antibodies from previous pathogen exposure and vaccinations to neutralize virus in the plasma. In general, higher drying temperatures and extended dwell times reduce pathogen survival, based on work with Pseudorabies, Porcine Reproductive and Respiratory Syndrome, Swine Vesicular Disease Virus, Classical Swine Fever, Salmonella, E. coli K88 and E. coli K99. To date, no experiment involving the feeding of commercial spray dried plasma protein has demonstrated transmission of PCV2.
In summary, it is not appropriate to conclude that the experimentally produced plasma product fully represents commercially produced spray dried porcine plasma used in the swine industry today. Collaborative research in this area is in progress.
Sincerely,
| Tanja Opriessnig, DVM, PhD Assistant Professor, Veterinary Pathologist Veterinary Diagnostic Laboratory College of Veterinary Medicine Iowa State University Phone: 515-294-1950 Email: tanjaopr@iastate.edu |
Abby Patterson, DVM, MS Adjunct Instructor, Graduate Student College of Veterinary Medicine Iowa State University Phone: (515) 294-1950 Email: aguard@iastate.edu |
| Pat Halbur, DVM, MS, PhD Professor and Chair Dept of Veterinary Diagnostic & Production Animal Medicine Executive Director – ISU Veterinary Diagnostic Laboratory Iowa State University College of Veterinary Medicine Phone: (515)294-6970 Email: pghalbur@iastate.edu |
Louis E. Russell, PhD Chairman North American Spray Dried Blood & Plasma Producers Phone: (515) 289-7607 Email: louis.russell@functionalproteins.com |