JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

October 2017

P-V23

 

Signalment (JPC #627741):  A six-month old colt

HISTORY:  This colt’s mother was immune to African horse sickness.  This animal had been vaccinated once against African horse sickness at three months of age.

HISTOPATHOLOGIC DESCRIPTION:  Lung:  Over 90% of alveoli are filled with abundant pale, eosinophilic, homogenous to fibrillar material (edema and fibrin) admixed with low numbers of macrophages, lymphocytes, and minimal hemorrhage.  Diffusely, alveolar septa are expanded up to 3 times normal diameter by fibrin, edema, markedly hypertrophied capillary endothelial cells, and few lymphocytes and macrophages.  Diffusely, interlobular septa, perivascular and peribronchial adventitia, subpleural connective tissue, and bronchiole-associated lymphoid tissue are moderately to markedly expanded by edema, fibrin, and low numbers of lymphocytes, plasma cells, and macrophages.  Endothelial cells within venules are swollen with vacuolated cytoplasm and large, reactive nuclei.  Multifocally bronchi and bronchioles contain moderate amounts of hemorrhage, fibrin, and edema.  In less affected areas, occasional alveolar lumina are confluent and lined by shortened alveolar septa with blunt, clubbed ends (emphysema).

MORPHOLOGIC DIAGNOSIS:  Lung: Edema, acute, multifocal,  severe, with reactive endothelium and mild interstitial pneumonia, breed unspecified, equine.

ETIOLOGIC DIAGNOSIS:  Orbiviral pneumonia

CAUSE:  African Horse Sickness virus (AHSV)

CONDITION:  African Horse Sickness

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

 TYPICAL GROSS FINDINGS:

 TYPICAL LIGHT MICROSCOPIC FINDINGS:

 ULTRASTRUCTURE:

 ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

 Orbiviruses:  Vasculitis-induced lesions

 REFERENCES:

  1. Lopez A, et al. Respiratory system, mediastinum and pleurae. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Mosby Elsevier; 2016: 526.
  2. Miller LM, Gal A. Cardiovascular system and lymphatic vessels. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Mosby Elsevier; 2016: 603-604.
  3. Robinson WF, Robinson NA. Cardiovascular system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. Philadelphia, PA: Elsevier; 2016:72-74.
  4. Weyer C, Grewar JD, Burger P, Rossouw E, Lourens C, Joone C, et al. African horse sickness caused by genome reassortment and reversion to virulence of live, attenuated vaccine viruses, South Africa, 2004–2014. Emerg Infect Dis. 2016;22(12):2087-2096.
  5. Zachary JF. Mechanisms of microbial infections. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Mosby Elsevier; 2016:212-214.


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