Whats your diagnosis #3
Porcine Multisystemic Wasting Syndrome – PCV-2
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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.
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.
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.
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.
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.
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
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.
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.