Quantification of porcine circovirus type 2 (PCV2) DNA in serum and tonsillar, nasal, tracheo-bronchial, urinary and faecal swabs of pigs with and without postweaning multisystemic wasting syndrome (PMWS)

Abstract

The present study focused on PCV2 quantification by TaqMan PCR in nasal (n=99), tonsillar (n=108), tracheo-bronchial (n=72), urinary (n=91) and faecal (n=42) swabs, as well as in serum (n=57), from a total of 146 pigs received at the Pathological Diagnostic Service at the Veterinary School of Barcelona (Spain). Animals were classified into three categories based on histopathological and in situ hybridisation (ISH) results: PMWS affected pigs (Group A, n=42), PCV2 subclinically infected pigs (Group B, n=29), and non-PMWS with PCV2 ISH negative pigs (Group C, n=75). Overall, tracheo-bronchial swabs had the higher PCV2 load followed by serum, tonsillar, nasal, faecal and, finally, urinary swabs. PCV2 genome was also detected in different proportions in all three categories of pigs; in all tested sites, viral load means were significantly higher (P<or=0.02) in animals with PMWS (Group A pigs) than in animals without PMWS (Group B and C pigs). Therefore, the more severe the lesions, the higher amounts of viral genome by ISH, and the higher PCV2 load in serum and swab specimens. Except for the tracheo-bronchial swab, no significant differences (p>0.05) were observed among tested specimens when age-groups (pigs younger than 1.5 months, and equal or older than 1.5 months of age) were compared. In summary, PCV2 is presumably excreted through respiratory (nasal and tracheo-bronchial) and oral (tonsillar) secretions, urine and faeces of both PMWS and non-PMWS affected pigs, with higher viral loads being associated with the presence of PMWS lesions.