JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

October 2017

P-V18

 

SIGNALMENT (JPC Accession #4048859): Four-week old male crossbred pig (Sus scrofa)

HISTORY: A respiratory disease in a pig herd quickly spread from the finishing unit to the growing and breeding units. The affected animals showed prostration with respiratory signs including sneezing. The disease disappeared two weeks after onset, except in the breeding unit. The presently examined pig was one of two in the breeding unit submitted for necropsy.

HISTOPATHOLOGIC DESCRIPTION: Lung: Affecting approximately 40% of this section, there are multifocal areas of atelectasis and consolidation centered around or adjacent to bronchi and bronchioles.  Diffusely affecting the bronchioles, and to a lesser extent the bronchi, the epithelium is circumferentially  either attenuated, degenerate and/or necrotic, sloughed and replaced by karryorhectic and cellular debris with infiltrating macrophages, neutrophils, lymphocytes, and plasma cells.  This necrotic and inflammatory material variably fills bronchial and bronchiolar lumina which are mildly to moderately ectatic.  The epithelium of less affected bronchi is often hyperplastic up to three cell layers thick, forming folds into the lumina or eroded and replaced by similar necrosis and inflammation which infiltrates through the lamina propria.  Surrounding alveolar septa are diffusely thickened up to three times normal by lymphocytes, plasma cells, macrophages, and type II pneumocyte hyperplasia.  Alveolar septa are often fragmented and necrotic with karryorhectic and cellular debris extending into the alveolar lumina which contain scattered neutrophils, macrophages, fibrin, and necrotic debris.  There is mild perivascular and interlobular edema, and vessels often have hypertrophied endothelium.

MORPHOLOGIC DIAGNOSIS: Lung: Pneumonia, bronchointerstitial, necrotizing, multifocal, moderate, with type II pneumocyte hyperplasia, crossbred pig, porcine.

ETIOLOGIC DIAGNOSIS: Orthomyxoviral pneumonia

CAUSE:  Swine orthomyxovirus (Influenza A virus)

CONDITION: Swine Influenza

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS: 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURAL FINDINGS: 

ADDITIONAL DIAGNOSTIC TESTS: 

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

References:

  1. Caswell JL, Williams KJ. Respiratory system. In: Maxie MG. ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2017:526-527, 567, 577, 587.
  2. Constable PD, Hinchcliff KW, Done SH, Grünberg W. Veterinary Medicine: A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs, and Goats. 11th ed. St. Louis, MO: Elsevier; 2017:1075-1085.
  3. Detmer SE, Gramer MR, Goyal SM, Torremorell M. In vitro characterization of influenza A virus attachment in the upper and lower respiratory tracts in pigs. Vet Pathol. 2012;50(4):648-658.
  4. Janke BH. Influenza A virus infections in swine: Pathogenesis and diagnosis. Vet Pathol. 2014;51(2):410-426.
  5. Löhr CV, et al. Pathology and viral antigen distribution of lethal pneumonia in domestic cats due to pandemic (H1N1) 2009 influenza A virus. Vet Pathol. 2010; 47(3): 378-386.
  6. Sutherland-Smith M. Suidae and tayassuidae (wild pigs, peccaries). In: Miller RE, Fowler ME. eds. Fowler’s Zoo and Wild Animal Medicine. 8. St. Louis, MO: Elsevier Saunders; 2015:576.
  7. Watson CE, Bell C, Toohey-Hurth K. H3N2 canine influenza virus infection in a dog. Vet Pathol. 2017;54(3):527-530.
  8. Yoon KJ, Schwartz K, Sun D, Zhang J, Hildenbrandt H. Naturally occurring influenza A virus subtype H1N2 infection in Midwest United States mink (Mustela vison) J Vet Diagn Invest. 2012; 24(2): 388-391.
  9. Zachary JF. Mechanisms of microbial infections. In: Zachary JF. ed. Pathologic Basis of Veterinary Disease. 6th ed., St. Louis, MO: Elsevier; 2017:207, 210.


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