CReSA Studies Boundary between PMWS and PRC14 August 2013
SPAIN - Researchers at the Centre for Research in Animal Health (CReSA) have published a retrospective study indicating that pulmonary diseases caused by porcine circovirus type 2 are probably insignificant, whereas systemic infections by porcine circovirus type 2 contribute greatly to porcine respiratory complex (PRC).
The porcine respiratory complex is a clinical presentation characterised by respiratory signs and growth retardation in pigs. Morbidity ranges between 10 and 40 per cent and mortality between two and 20 per cent.
CRP injuries are multifactorial in etiology, being circovirus type 2 (PCV2) - a pathogen potentially involved in the presentation of this complex. PCV2 has been particularly associated with PMWS or PCV2-associated systemic disease, but some studies have indicated that injuries can cause respiratory damage in the absence of the systemic lymphoid. This condition is apparently different and is known as pulmonary disease PCV2 (PCV2-EP).
The study retrospectively analysed the relationship between CRP and the PCV2 infection from a pathological perspective.
In 317 selected pigs suffering from CRP that underwent autopsy between 1998 and 2011, the most prevalent injuries were subacute interstitial pneumonia (27.7 per cent) and the combination of interstitial pneumonia with subacute catarrhal-purulent bronchopneumonia (28.4 per cent).
A total of 226 pigs tested positive for PCV2 hybridization in situ (HIS). Of these, 184 suffered from CP. The remaining 42 pigs that tested positive for PCV2 had no lymphoid lesions and showed a low amount of viral nucleic acid in these tissues and, therefore, did not qualify as CP. Only nine were positive for PCV2 by HIS in concomitant lung, even in low amounts.
In conclusion, all positive cases by HIS in PCV2-CRP showed evidence of systemic viral infection. These results indicate that PD-PCV2 is probably an insignificant disease and PCV2 contributes greatly to the CRP.
Ticó G Segalés J, Martinez J. The blurred border between Porcine circovirus type 2-systemic disease and Porcine respiratory disease complex. Vet Microbiol. 3 May 2013, 163 (3-4) :242-7.
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