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Studies on the epidemiology, early pathogenesis and control of Porcine Circovirus Diseases (PCVDs)

Final Report Summary - PCVD (Studies on the epidemiology, early pathogenesis and control of Porcine Circovirus Diseases (PCVDs))

Porcine circovirus diseases (PCVD) was first identified in 1991, in Canada. Newly weaned pigs were primarily affected. The consequences of the disease were not severe at this stage. Since 1991 various versions of PCVD have been confirmed in Canada, the Unites States and Europe. The newer version of the disease seems a lot more severe and also affects older pigs. This form of PCVD was first identified in Europe and is often referred to as the European strain.

PCV associated diseases are now recognised all over the world. Most pig populations are serologically positive for PCV-2, although they do not necessarily show signs of disease. The Porcine Circovirus alone does not cause disease. Management practices, feeding and other viruses (e.g. PRRSV) also play a part in disease development. It is also believed that part of the explanation as to why some pigs are more severely affected than others could be an inheritable natural resistance or an inheritable increased susceptibility to PCV-2. An increased susceptibility to developing PCVD's has been seen in offspring from specific boar lines.

The project brought together a multidisciplinary scientific team of 15 partners representing diagnostic institutes, universities, and industry. This project established an EU-led multidisciplinary consortium containing expertise in epidemiology, pig genetics, pig nutrition, pathology, molecular biology, immunology, vaccinology, bacteriology and PCV virology to generate scientifically sound information on the aetiology and early pathogenesis of PCVDs.

The project met all the objectives and the information generated has been used to generate control measures for PMWS / PCVD resulting in the reduction of use of antibiotics and secondary zoonotic bacterial infections, meeting consumer concerns for quality / safety of pork products.

At the initiation of this project, very little was known about the pathogenesis of PMWS, except that PCV2 was the necessary causal agent and that this virus appeared to act as an immunosuppressive viral agent, inducing lymphoid tissues lesions and progressive growth retardation in infected pigs. Early target cells for PCV2 replication had not been clearly identified although very high PCV2 loads had been found within Dendritic cells (DC) where the virus was able to escape lysis and to stay unprocessed in large quantities for a long period of time. Foetuses were known to be sensitive to PCV2 infection In pigs, experimental acute clinical cases with greater than 50 % incidence were obtained only when pigs were younger than three to four weeks of age.

Diseases associated with PCV2 continue to have a major impact on pig production throughout the EU although reports of results from vaccination have been very promising. Interest remains high in control measures and the ready provision of access to the most recent research findings through was much appreciated by industry. COPA-COGECA welcomed the updates through their working group on pigs in particular. The information dissemination work package made good progress and through its proactive approach achieved its milestones and deliverables communicating the results of research not just at a scientific level but also at a practical level. It is important that similar projects in the future also seek to reach beyond the scientific community to those with a practical responsibility for the health and welfare of pigs. Overall the interactions between the STREP and the NMSACC-PCVD consortia were very positive and there were benefits from the collaboration for partners in both of the projects. The collaboration could form a template for similar projects in the future.