Characterization of a new disease syndrome associated with porcine circovirus type 2 in previously vaccinated herds

Abstract

Porcine circovirus-associated disease (PCVAD) encompasses a group of wasting syndromes linked to porcine circovirus type 2 (PCV2). This paper describes a new PCV2 disease syndrome, called acute pulmonary edema (APE), which, unlike other PCVAD syndromes, has a peracute onset and is associated with herds vaccinated for PCV2.

Fig. 1.

Anatomical and microscopic features associated with APE. (A) Thoracic cavity from a pig that died acutely. The thorax contains a large amount of serosanguineous fluid, and the lungs are markedly edematous and possess dark red areas of consolidation. (B) Hematoxylin-eosin-stained thin section from a lung showing interstitial infiltration of macrophages, lymphocytes, and plasma cells and fibrinoid necrosis of the smooth muscle in the wall of an artery (arrows). Bar = 50 μm. (C) Hematoxylin-eosin-stained lung thin section with pulmonary edema, showing a marked distention of the tissue surrounding an artery (arrows). Bar = 50 μm. (D) IHC staining for PCV2 antigen in an affected lung. Note the cytoplasmic staining of many cells (mononuclear cells), which are free within the lumen of an artery. Also note the nuclear staining in an endothelial cell lining the artery (arrow). Tissue was counterstained with hematoxylin. Bar = 25 μm.

Fig. 2.

Comparison of APE-associated PCV2 ORF2 peptide sequence D71923 with those of representative historical isolates. Historical sequences were obtained during the 2009 outbreaks of PCVAD in Kansas (14). Sequences were aligned by using CLUSTAL X (30).