ADVANCES IN PORCINE CIRCOVIRUS TYPE 2 (PCV2) RESEARCH: RESULTS OF THE EUROPEAN PROJECT NO. 513928: CONTROL OF PORCINE CIRCOVIRUS DISEASES (PCVDs) TOWARDS IMPROVED FOOD QUALITY AND SAFETY
G.M. Allan

Abstract
A case definition has now been arrived at. However, not all clinical signs and not all pathological lesions will be seen in one animal. The occurrence of PMWS (Post-weaning multi-systemic wasting syndrome) is characterised by an excessive increase in mortality and wasting post-weaning compared with the historical level in the herd. At least 5 pigs per herd should be subjected to post-mortem examination.

Clinical signs include growth retardation and wasting, enlargement of lymph nodes, dyspnoea, diarrhoea and jaundice.

Presence of moderate to severe characteristic histopathological lesions in lymphoid tissues with lymphiotic depletion, together with histiocytic infiltration and/or inclusion bodies and/or giant cells. The confirmation is by using immunohistochemistry or in-situ hybridisation.

Porcine circovirus type 2 may also be associated with reproductive disease, proliferative and necrotising pneumonia, PDNS, respiratory disease, and sow abortion and mortality syndrome.

A considerable amount of work is continuing into the possibility that high viral load is indicative of PMWS. The target will appear to be cells of the macrophage/monocyte system. The primary site of replication has still not been discovered. The effect of other agents in the pathogenesis of PMWS has still not been fully worked out and this has led to the search for more pathogenic genotypes, e.g. three distinct genotypes in Sweden.

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