Nonsuppurative Myocarditis Caused by Porcine Circovirus Type 2 in a Weak-Born Piglet

Abstract

ABSTRACT. Reproductive failure associated with porcine circovirus type 2 (PCV2) was observed in a farm, and a weak-born 8-day-old piglet was examined pathologically. Focal to locally extensive lesions, including infiltration of macrophages and lymphocytes, fibrosis and degeneration of the myocardium were observed in the heart. PCV2 antigens and nucleic acids were detected in degenerated cardiomyocytes and macrophages infiltrating the heart by immunohistochemical staining and in situ hybridization. Depletion of lymphocytes with occasional infiltration of multinucleated giant cells was seen in the lymphoid organs and PCV2 antigens were demonstrated in histiocytic cells. Crystalline arrays of viral particles were observed in infiltrated macrophages in the heart and, rarely, in cardiomyocytes by electron microscopy. Although myocarditis is a common finding in aborted or stillborn piglets in reproductive failure due to PCV2, it was also observed in the 8-day-old piglet with PCV2 association. KEY WORDS: myocarditis, porcine circovirus type 2, reproductive failure.J. Vet. Med. Sci. 67 (7): [735][736][737][738] 2005 Porcine circovirus type 2 (PCV2) is known as the causative agent for postweaning multisystemic wasting syndrome (PMWS), which is characterized by wasting or unthriftiness, dyspnea and jaundice [11,20]. PCV2 was also related to porcine dermatitis and nephropathy syndrome (PDNS) and reproductive failure [7,12,17,23]. Several reports suggested that nonsuppurative myocarditis is a common microscopic finding in PCV2-infected fetuses [17,19,23]. In this report, we focus on a weak-born piglet that died at 8 days old in a chain of PCV2-associated reproductive failure.The herd was a 177-sow, farrow-to-finish operation and was kept under good hygienic conditions. Reproductive failure including mummified fetuses and late-term dead fetuses occurred on the farm from June to August, 2001. The gilts had been vaccinated for Japanese encephalitis virus (JEV), porcine parvovirus (PPV) and Bordetella bronchiseptica. The herd was free from classical swine fever (CSF), Aujeszky's disease (AD) and porcine reproductive and respiratory syndrome (PRRS). PMWS and PDNS had been never found on the farm before the occurrence of reproductive failure.One gilt in the farm farrowed seven dead fetuses including autolyzed fetuses and one weak-born piglet. This piglet died at 8 days old and was necropsied for etiology. Mild to moderate enlargement of the superficial lymph nodes was observed at the necropsy. Tissue samples were fixed in 10% neutral buffered formalin, routinely paraffin-embedded and sectioned at 4 µm for hematoxylin and eosin stain, Masson trichrome stain (MT), phosphotungstic acid hematoxylin stain (PTAH), immunohistochemical staining (IHC) [9] and in situ hybridization (ISH) for PCV2. For ISH, sections were deparaffinized and pretreated by 40 µg/ml proteinase K solution at 37°C for 20 min and 0.2 M HCl at room temperature for 10 min. PCR product (primer pair; 5'-A G A A G G G T T G G G G G A T T G T A T G -3 ' a n d 5 ' -GG...

Lawsonia intracellularis and Porcine Circovirus type-2 infection in Estonia

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PMWS-like Lesions in Preweaned Crossbred Piglets Naturally Infected with Porcine Circovirus 2 in India

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