Comparison of porcine circovirus type 2 load in serum quantified by a real time PCR in postweaning multisystemic wasting syndrome and porcine dermatitis and nephropathy syndrome naturally affected pigs.

Postweaning multisystemic wasting syndrome (PMWS) diagnosis is based on the presence of characteristic histopathological lymphoid lesions and porcine circovirus type 2 (PCV2) within these lesions. Previous studies indicate that PCV2 load is higher in PMWS affected than in PCV2 infected, healthy pigs. On the other hand, PCV2 has been suggested to play a role in porcine dermatitis and nephropathy syndrome (PDNS) pathogenesis. This study describes a new TaqMan real time PCR assay and its use to quantify viral load in serum samples. Serum viral loads were related with different degrees of PMWS characteristic lesions and PDNS cases. DNA extracted from serum samples from 75 animals with mild, moderate and severe PMWS lesions and 12 animals with PDNS was used as template. PCV2 DNA was quantified in 69 of 75 PMWS cases and in 11 of 12 PDNS cases. Significant differences in PCV2 load were observed between animals with severe, moderate and mild PMWS lesions, although variability within each group was high, probably due to heterogeneity in disease progression. These results suggest that high viral load is a major feature of PMWS affected pigs. PDNS affected animals had lower PCV2 loads. No significant differences in viral load were found between animals suffering from PDNS and animals with mild PMWS characteristic lesions, which were unaffected clinically.