Young male York-shire/Hampshire cross pig (Sus domestica).Two piglets (about three-weeks-old) had been growing slowly and showed respiratory symptoms with rapid breathing. They were both treated with antibiotics (penicillin) but died suddenly. The piglets were sent to necropsy. A few weeks later a small number of fattening pigs had reduced growth rate and were in poor body condition, the pigs were euthanized and sent to necropsy.  All pigs were from the same specific pathogen-free farm (SPF). The submitted slide is from one of the fattening pigs.

Once a year tests are taken to show freedom from: swine influenza virus, Actinobacillus pleuropneumoniae (APP), Mycoplasma hyopneumoniae (SEP), Sarcoptes scabiei, Swine dysentery (Brachyspira hyo-dysenteriae), Intestinal spirochetosis (Brachyspira pilosicoli), other Brachyspira-subspecies, toxin-producing Pasteurella multocida, Salmonella and Lawsonia intracellularis. The farm was not vaccinated against PCV-2.

Gross Description:  

At necropsy, the fattening pig was in poor body condition and presented with a mottled myocardium, enlarged lymph nodes, multiple white foci scattered throughout the kidneys, firm cranioventral lung, and mild ascites. The two piglets were in poor body condition, the hearts had marked dilatation of left and right ventricle and atrium (dilated cardio-myopathy) and the piglets presented signs of cardiac failure with acute stasis in liver, ascites, and pulmonary edema.

Histopathologic Description:

Heart: Multifocal to coalescing chronic severe granulomatous interstitial inflammation with loss of myocytes is present. The inflammatory cells are dominated by lymphocytes, plasma cells, and macrophages with fewer neutrophils and eosinophils. Few multinucleated giant cells are also seen. Multifocally, the myocytes are degenerated or necrotic with loss of striations and eosinophilic swollen cytoplasm, loss of nuclei, and occasionally pyknotic nuclei, scattered degenerated Purkinje fibers are also seen. Multifocally, there are small foci of basophilic homogenous material (mineralization). The outer walls of medium and large sized vessels are infiltrated by varies amount of mononucleated inflammatory cells and the vessels have marked thickened tunica adventitia due to inflammation and edema, multifocal small sized vessels have degenerated walls with infiltration of mixed inflammatory cells (vasculitis). The endocardium is moderately thickened with abundant mixed inflammatory cells, reactive fibroblasts and angiogenesis (granulation tissue). On the Masson trichrome stain, there is a moderate amount of extracellular collagen present in areas with myocyte loss and with reactive fibroblasts.

Morphologic Diagnosis:  

Heart: Myocarditis and endocarditis, multifocal to coalescing, interstitial, severe, chronic, lymphoplasmacytic and histiocytic with multinucleated giant cells (granulomatous) and vasculitis.

Lab Results:  

Immunohistochemistry heart: positive for PCV-2 (piglet). PCR lymph node: Positive for PCV 2 (fattening pig).


Myocarditis and endocarditis/PCV-2

Contributor Comment:  

Porcine circovirus (genus Circovirus, family Circoviridae) is a small (17nm diameter), non-enveloped virus that contains circular single-stranded DNA.3,8 The virus was initially discovered in 1998 and was first isolated from pigs with post weaning multisystemic wasting syndrome (PMWS). The virus is highly prevalent in the domestic pig population all over the world and PCV-2 infection is common in herds as a subclinical disease. PCV-2 infection has been associated with several disease complexes including PMWS, enteric disease, respiratory disease, porcine dermatitis and nephropathy syndrome and reproductive disorders.3,8,10 Vaccine against PCV-2 has been used since 2006, which have been effective controlling and preventing PCV-2 associated diseases. Although the majority of the conventional pigs entering the market are now vaccinated, PCV-2 still remains an important differential diagnosis for various disease manifestations in pigs.8 In PMWS, pigs exhibit a systemic infection involving several organ systems and the disease is characterized by loss of weight or wasting in combination with various other clinical signs such as dyspnea, diarrhea, pallor, and jaundice. Other clinical signs include coughing, fever, central nervous signs, or sudden death.3,8 On gross necropsy, lymphadenopathy is the most consistent feature of PMWS, but the gross lesions and severity are highly variable.8  Diagnosis is mainly based on clinical findings and typical gross and histological lesions, and is supported by demonstration of active PCV2 infection by immuno-histochemistry or PCR. 3

Porcine circoviral antigen and nucleic acid are most consistently present in the cytoplasm of monocytes, macrophages and dendritic cells throughout the body. Vascular smooth muscle and endothelial cells occasionally express circoviral antigen.3 PCV2 induces characteristic lesions in the lymphoid system which includes lymphoid depletion and granulo-matous inflammation with multi-nucleated giant cells, lesions are commonly observed in the tonsils, spleen, Peyer´s patches, and lymph nodes. In the respiratory system, bronchinterstitial pneumonia may be a feature and the virus can cause meningoencephalitis and vasculitis in CNS. In the digestive system, the most frequent lesion is granulomatous enteritis characterized by increased number of macrophages and scattered multinucleated giant cells in the mucosa and submucosa of the ileum and occasionally the colon and cecum. In the kidney, lesions are characterized by lymphoplasmacytic or granulomatous interstitial nephritis. In the vascular system, PCV2 antigen has been demonstrated in endothelial cells and in inflammatory cells in the arterial walls and chronic lymphoplasmacytic vascular lesions has been described among pigs infected with PCV2.8,10 In foetuses, lesions are most prominent in the cardiovascular system, especially in the heart where cardio-myocytes are degenerated, or lost and replaced by fibrous connective tissue. In addition, there is non-suppurative myo-carditis and occasionally multinucleated giant cells.2,6, 8,11  Heart failure and dilated cardiomyopathy is described as a feature among aborted foetuses and very young animals secondary to myocarditis.2,6,8,11

The presented case from the pig-farm showed typical gross and histological lesions of PCV2 infection that are compatible with the described cases in the literature. The fattening pig had lymphoid depletion and granulomatous inflammation in lymph node and granulomatous inflammation with vasculitis in kidney and heart. A purulent bronchopneumonia was seen in the lungs; however, the material was not cultured but secondary bacterial infection is most likely. The two young piglets with dilated cardiomyopathy had chronic granulomatous myocarditis at on histopathology. The diagnosis was supported by demonstrating active PCV2 infection with PCR and immuno-histochemistry.

JPC Diagnosis:  

Heart: Pancarditis, transmural, lymphohistiocytic, multifocal to coalescing, marked, with vasculitis, myocardial loss, and fibrosis, York-shire/Hampshire cross pig, Sus domestica.

Conference Comment:  

The contributor provides an excellent summary of porcine circovirus-2 (PCV-2) infection in swine. There are two separate genotypes of PCV have been implicated in this species. PCV type 1 (PCV-1) is generally thought to be nonpathogenic and does not cause disease in pigs, although it has been implicated as a potential cause of congenital tremors in newborn piglets.3 PCV-2 is pathogenic in pigs and causes post weaning multisystemic wasting syndrome (PMWS) discussed by the contributor above. PMWS is a multifactorial systemic disease and clinically manifests at 25-150 days of age with most cases occurring between 7 and 15 weeks.3-6,9 The six fundamental clinical signs include wasting, dyspnea, lymphadenopathy, diarrhea, pallor, and jaundice. Coughing, fever, gastric ulceration, and meningitis have also been reported. Serum antibodies to PCV-2 are very common in swine herds around the world, and positive antibody titer does not necessarily equate to clinical PMWS.3 However, co-infection of PCV-2 with porcine reproductive and respiratory syndrome virus (PRRSV), and/or porcine parvovirus (PPV), produces more severe clinical disease; although, PCV-2 has been shown to be sufficient to produce disease in susceptible animals without co-infection.3,4,6,9,10

Conference participants discussed that lymphoplasmacytic and histiocytic myo-carditis with varied numbers of multi-nucleated giant cells and myocardial degeneration, loss, and replacement by fibrosis are typical histologic changes associated with infection by PCV-2.3,4 In addition, necrotizing vasculitis, a key histologic feature in this case, has been implicated as a hallmark lesion in PCV-2 infection, as well as the severe form of systemic porcine circovirus-associated disease (PCVAD), discussed below.1-3,9 Participants also noted the lack of unique and characteristic intracytoplasmic baso-philic botryoid viral inclusion bodies, typically associated with PCV-2 infection. Inclusion bodies may be present within macrophages; however, they are not always identified. Definitive diagnosis of PMWS is based on a combination of typical clinical signs of disease, typical histologic lesions, and detection of PCV-2 in affected tissues via immunohistochemistry, as demonstrated by the contributor in this case. 3 As mentioned above, infection with PCV-2 alone can cause disease in pigs; however, it is more commonly identified in a complex of multiple pathogen infection, known as PCVAD.  This syndrome results from co-infection of PCV-2 with PPV, PRRSV, encephalomyocarditis virus (EMCV), swine influenza virus, or Mycoplasma hyo-pneumonia, or a combination of these agents.1,3,4,10 It can also occur from PCV-2 infection in association with recent vaccination.3,4 Despite the economic losses caused by PCV-2, PMWS, and PCVAD, the pathogeneses underlying the clinical findings remain largely unclear; however, they are likely related to macrophage activation prior to infection and subsequent endothelial cell modulation.7 Conference participants discussed that antigens for PCV-2 can be found in macrophages, monocytes, and dendritic cells, as well as endothelial cells and vascular smooth muscle.


1. Allan GM, Ellis JA. Porcine circoviruses: A review. J Vet Diagn Invest. 2000; 12:3-14.
2. Brunborg IM, Jonassen CM, Mildal T, et al. Association of myocarditis with viral load of porcine circovirus type 2 in several tissues in cases of foetal death and high mortality in piglets. A case study.  J Vet Diagn Invest 2007; 19:368-375
3. Caswell JL and Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy and Palmer´s. Pathology of Domestic Animals 6th ed Vol. 2. St Louis, MO: Elsevier Saunders; 2016:527-529.
4. Cushing TL, Steffen D, Duhamel GE. Pathology in practice: Myocarditis attributable to PCV-2 infection in a pig fetus. J Am Vet Med Assoc. 2013; 242:317-319.
5. Harding JC. The clinical expression and emergence of porcine circovirus 2. Vet Microbiol. 2004; 98:131-135.
6. Madson DM, Patterson AR, Ramamoorthy S, et al. Effect of Porcine Circovirus Type 2 (PCV2) vaccination of the dam on PCV2 Replication in utero. Clinical and vaccine immunology. 2009; 830-834.
7. Marks FS, Almeida LL, et al. Porcine circovirus 2 (PCV2) increases the expression of endothelial adhesion/junctional molecules. Braz J Microbiol. 2016; 47:870-875.
8. Opressnig T, Janke BH and Halbur PG. Cardiovascular lesions in pigs naturally or experimentally Infected with porcine circovirus type 2. J Comp. Path. 2006; 134:104-110.
9. Opriessnig T, Langohr I. Current state of knowledge on porcine circovirus type 2-associated lesions.  Vet Pathol. 2012; 50(1):23-33.
10. Segalés J. Porcine circovirus type 2 (PCV2) infections: Clinical signs, pathology and laboratory signs. Virus Res. 2012; 164:10-19.
11. West KH, Bystrom JM, Wojnarowicz C, Shantz N, et al. Myocarditis and abortion associated with intrauterine infection of sows with porcine circovirus 2. J Vet Diagn Invest. 1999; 11:530-532

Click the slide to view.

2-1 Heart, piglet.

2-2 Heart, piglet.

2-3 Heart, piglet.

2-4 Heart, piglet.

2-5 Heart, piglet.

2-6 Heart, piglet.

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