JPC SYSTEMIC PATHOLOGY
CARDIOVASCULAR SYSTEM
APRIL 2019
C-B02

Signalment (JPC #1482029):  5-month-old guinea pig

HISTORY:  This animal died following a brief period of depression and anorexia. 

HISTOPATHOLOGIC DESCRIPTION (Slide 6a):  Heart:  The epicardium is diffusely replaced by an adherent, variably thick (up to 1mm) mat of pale eosinophilic, homogenous to fibrillar material (fibrin) that contains numerous enmeshed viable and degenerate heterophils, moderate numbers of erythrocytes (hemorrhage), eosinophilic cellular and karyorrhectic debris (necrosis), and fewer scattered lymphocytes, plasma cells, and macrophages.  The mat multifocally extends into the subjacent myocardium where it separates, surrounds, and replaces cardiomyocytes.  Subjacent to this infiltrate are reactive fibroblasts separated by minimal amounts of loose fibrous connective tissue and many perpendicular, evenly spaced, small caliber blood vessels lined by hypertrophic endothelium (granulation tissue).  Multifocally, vessel lumina are partially to completely occluded by adherent fibrinocellular thrombi that contain enmeshed heterophils, macrophages, and fewer lymphocytes and plasma cells, and endothelial cells are often hypertrophic. There is focal mild chondrous metaplasia within tunica media of the proximal ascending aorta.

(Slide 6b):  Heart (Brown & Brenn stain):  The fibrinous mat contains abundant scattered extracellular and intraheterophilic Gram-positive diplococci.

MORPHOLOGIC DIAGNOSIS:  Heart:  Epicarditis, fibrinosuppurative, chronic-active, diffuse, severe, with mild subepicardial myocarditis, fibrin thrombi, and abundant intralesional Gram-positive diplococci, guinea pig, rodent.

ETIOLOGY:  Streptococcus pneumoniae

ETIOLOGIC DIAGNOSIS:  Diplococcal (pneumococcal) epicarditis

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

Pericarditis in the guinea pig: 

Respiratory infection in the guinea pig: 

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Abee CR, Mansfeld K, Tardiff S, Morris T. Nonhuman Primates in Biomedical Research, Volume 2: Diseases. San Diego, CA: Academic Press; 2012:107-109,452-453.
  2. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents & Rabbits. 4th ed. Ames, IA: Blackwell Publishing Ltd; 2016:144-145,186,230.
  3. Lopez A, Martinson SA. Respiratory system, mediastinum, and pleurae, In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2016:518.
  4. Lowenstine LJ, McManamon R, Terio KA.   In: Terio KA, McAllose D, St. Leger J, eds.  Pathology of Wildlife and Zoo Animals.  San Diego, CA: Elsevier; 2018:387, 392.
  5. Matz-Rensing K, Lowenstine LJ. New world and old world monkeys.  In: Terio KA, McAllose D, St. Leger J, eds.  Pathology of Wildlife and Zoo Animals.  San Diego, CA: Elsevier; 2018:363, 364.
  6. Miller AD, Zachary JF. Nervous system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th St. Louis, MO: Mosby Elsevier; 2016: 836-837.
  7. Robinson WF, Robinson NA. Cardiovascular system.  In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016:25-32.
  8. Swennes AG, Fox JG. Bacterial and mycoplasmal diseases. In: Fox JG, Marini RP eds. Biology and Diseases of the Ferret. 3rd ed. Ames, IA: Wiley Blackwell; 2014:520.


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