Porcine Multisystemic Wasting Syndrome – PCV-2


Whats your diagnosis #3

Porcine Multisystemic Wasting Syndrome – PCV-2

See original post here

History: A feeder pig was found dead in the morning, it was thinner than its penmates.

Gross Necropsy: (no photos)

The lungs were loosely adhered to the thoracic body wall by multiple strands of fibrin. The lungs were diffusely edematous and firm.

The pericardium contained approximately 200 mls of fluid. The right ventricle was severely enlarged and the pulmonary trunk was dilated.

There was diffuse serous atrophy of fat.

Histopathology:

Lungs: Alveolar septa contain large numbers of lymphocytes, macrophages, plasma cells and lesser numbers of neutrophils and eosinophils. Small bronchioles and a few alveoli contain neutrophils. There are perivascular infiltrates of lymphocytes and macrophages. Within the walls of arterioles there are neutrohilic and lymphocytic infriltrates and there is vacuolar degeneration of the tunica media. There is proliferation of fibrous tissue which occludes the lumens of multifocal small arterioles and bronchioles.

Lung: Vasculitis and perivasculitis, proliferative, and bronchointerstitial pneumonia

Lung: Vasculitis and perivasculitis, proliferative, and bronchointerstitial pneumonia

Kidneys: The renal interstitium is infiltrated with large numbers of lymphocytes, macrophages, and plasma cells with lesser numbers of neutrophils and eosinophils. There are macrophages containing multiple basophilic round cytoplasmic inclusions.

Kidney:  Interstitial nephritis, eosinophilic and granulomatous

Kidney: Interstitial nephritis, eosinophilic and granulomatous

Kidney, renal cortical tubule: Sloughed necrotic epithelial cells with basophilic cytoplasmic inclusions in epithelial cells and macrophages

Kidney, renal cortical tubule: Sloughed necrotic epithelial cells with basophilic cytoplasmic inclusions in epithelial cells and macrophages

Lymph nodes: There is diffuse lymphoid depletion characterized by loss of lymphoid follicles and germinal centers. There are moderate numbers of multinucleated giant cells in the medullary sinuses along with moderate numbers of lymphocytes, neutrophils, macrophages, and some eosinophils.

Lymph node:  Granulomatous lymphadenitis- Macrophages and multinucleated giant macrophages replace normal architecture

Lymph node: Granulomatous lymphadenitis- Macrophages and multinucleated giant macrophages replace normal architecture

Spleen: There is diffuse lymphoid depletion in the spleen similar to the lymph node.

Ileum: There is diffuse lymphoid depletion in the Peyer’s patches of the ileum, and there are large numbers of macrophages and lymphocytes infiltrating the submucosa along with small numbers of neutrophils.

Brain: There are a few foci of perivascular histiocytic and lymphocytic infiltrates in the brain stem.

Kidney, PCV-2 IHC: Strong immunoreactivity in tubular epithelial cells

Kidney, PCV-2 IHC: Strong immunoreactivity in tubular epithelial cells

Lung, PCV-2 IHC:  Strong immunostaining in macrophages around blood vessels

Lung, PCV-2 IHC: Strong immunostaining in macrophages around blood vessels

Lymph node, PCV-2 IHC:  The centers of follicles stain strongly with PCV-2 antigen

Lymph node, PCV-2 IHC: The centers of follicles are devoid of lymphocytes and macrophages/ dendritic cells stain strongly with PCV-2 antigen

Diagnosis:

1. Lungs: Interstitial pneumonia, granulomatous, severe, diffuse, with arteritis, perivasculitis, and multifocal proliferation of vascular fibrous tissue

2. Kidneys: Interstitial nephritis, granulomatous, multifocal, moderate, with intrahistiocytic basophilic cytoplasmic inclusions.

3. Brain: Perivasculitis, granulomatous, mild, multifocal

4. Spleen/Lymph nodes/ Ileum: Diffuse lymphoid depletion

5. Lymph nodes: Granulomatous lymphadenitis, moderate, diffuse

6. Ileum : Granulomatous enteritis, mild, multifocal

A feeder pig was presented for necropsy 12/8/08. This pig is thinner than its pen mates. It was found
dead 12/08/08 in the morning. The farm has had APP and Strep on the premises.

Comment:

The gross and microscopic lesions are consistent with PMWS, and PCV- 2 was detected in pooled tissues by PCR. No significant bacterial agents were isolated from the lymph node or intestines, and no bacteria were isolated from the lung. The PCR test for PRRSV was negative. An ELISA for swine flu was negative as well.

This case demonstrates the usefulness of histopathology as a diagnostic tool.  The gross lesions alone suggest polyserositis such as would be caused by Streptococcus suis or Haemophilus parasuis.  The histopathologic lesions of granulomatous inflammation with multinucleated giant macrophages and intracytoplasmic basophilic inclusions are specific for PCV-2 associated disease.  Immunohistochemistry and PCR confirmed the presence of PCV-2 antigen in the affected tissues, and other viruses (PRRS and Influenza) were ruled out by PCR and ELISA tests.

A diagnosis of PMWS is made based on 1) clinical signs of failure to grow, weight loss, and pneumonia, 2) typical histologic lesions including granulomatous lymphadenitis/ lymphoid depletion, and 3) detection of the virus in tissues by IHC or ISH.  Affected pigs are 5-18 weeks old and may have gastric ulcers, pleural and perioneal effusions and diarrhea.

Due to the ubiquitous presence of PCV-2 in swine herds and the broad variety of diseases that can involve PCV-2 it is proposed to introduce the term Porcine Circovirus Associated Disease (PCVAD).   PCVAD  can  be  subclinical  or  include  one or more of the following:  multisystemic disease with weight loss,  respiratory  signs,  PDNS,  diarrhea, and reproductive disorders.

Other proposed systems of classification of  PCVAD   includes: systemic infection (such as PMWS),  PCV2-associated  pneumonia,  PCV2-associated enteritis,  PCV2-associated  reproductive  failure,  and PCV2-associated  PDNS.

References:

Opriessnig T,  Xiang-Jin M, Halbur  P G.  2007. Porcine circovirus type 2–associated disease: Update on current terminology, clinical manifestations, pathogenesis, diagnosis, and intervention strategies.  J Vet Diagn Invest 19:591–615.

Advertisements

About Brian

Anatomic Pathologist, VetPath Services, Stone Ridge, NY- musculoskeletal, oral/dental, and sinonasal diseases
This entry was posted in Necropsy Cases and tagged , , , , , , . Bookmark the permalink.

One Response to Porcine Multisystemic Wasting Syndrome – PCV-2

  1. Francis Ian Roces says:

    it helps me a lot 🙂

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s