JPC SYSTEMIC PATHOLOGY
DIGESTIVE SYSTEM
October 2018
D-V05

Signalment (JPC# 1902055):  Sprague-Dawley rat

HISTORY:  Swellings of the anteroventral cervical area were noted in 3 Sprague-Dawley rats in a colony of 20 rats.

HISTOPATHOLOGY DESCRIPTION:  Salivary gland, submandibular and parotid:  Approximately 80 percent of the salivary adenomeres exhibit one of the following changes: shrunken acini with loss of central acinar lumina (atrophy); acini lined by swollen epithelial cells with vacuolated, lightly basophilic cytoplasm that are occasionally distended up to 20um by a large clear vacuole (degeneration); acinar cells with condensed, hypereosinophilic cytoplasm with pyknotic nuclei (necrosis); or acini are lost and replaced with fibrin, edema, mild hemorrhage and moderate numbers of neutrophils, fewer lymphocytes, plasma cells and macrophages.  Ducts are often lined by flattened epithelial cells (squamous metaplasia), are up to 5 cells thick with increased mitotic figures (ductular regeneration), or are occasionally lined by necrotic epithelial cells which slough into the lumen, and multifocally contain eosinophilic and karryorhectic cellular debris (necrosis).  Diffusely, the interstitium, interlobular septa, and periglandular tissue are expanded up to three times normal by edema, fibrin and hemorrhage admixed with previously described inflammatory cells, and blood vessels are often lined by reactive endothelium.  The parotid (serous) salivary gland is similarly but less severely affected.

Lymph node, mandibular:  There are large coalescing lymphoid follicles with prominent germinal centers that contain many tingible body macrophages.  The paracortex and medulla are mildly expanded by increased lymphocytes and low to moderate numbers of macrophages.  Blood vessels are mildly congested and there is moderate intranodal and perinodal hemorrhage.

MORPHOLOGIC DIAGNOSIS:

  1. Salivary glands, submandibular and parotid: Sialoadenitis, necrotizing, subacute, diffuse, moderate, with ductular squamous metaplasia and regeneration, Sprague-Dawley rat, rodent.
  2. Lymph node, mandibular: Lymphoid hyperplasia, diffuse, mild, with draining hemorrhage.

ETIOLOGIC DIAGNOSIS:  Coronaviral sialoadenitis

CAUSE: Rat coronavirus (Rat sialodacryoadenitis virus - SDAV)

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

Acute stage: 

ULTRASTRUCTURE:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016:27, 125-127.
  2. Bihun CGD, Percy DH. Morphologic changes in the nasal cavity associated with sialodacryoadenitis virus infection in the Wistar rat. Vet Pathol.  1995;32:1-10.
  3. Boorman GA, Eustis SL. Lung. In: Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds. Pathology of the Fischer Rat. San Diego, CA: Academic Press; 1990:348-349.
  4. Liang SC, Schoeb TR, Davis JK, Simecka JW, Cassell GH, Lindsey JR. Comparative severity of respiratory lesions of sialodacryoadenitis virus and sendai virus infections in Lewis and F344 rats. Vet Pathol. 1995;32:661-667.
  5. Macy JD, Weir EC, Barthold SW. Reproductive abnormalities associated with a coronavirus infection in rats. Lab An Sc. 1996;46:129-132.
  6. Neuenschwander SB, Elwell MR. Salivary glands. In: Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds. Pathology of the Fischer Rat. San Diego, CA: Academic Press; 1990:35-36.
  7. Williams DL. Laboratory animal ophthalmology. In: Gelatt KN, ed. Veterinary Ophthalmology. 3rd ed. Philadelphia, PA: Lippincott, Williams, Wilkins; 1999:1214-1215.
  8. Holmberg BJ. Ophthalmology of exotic pets.  In: Maggs DJ, Miller, PE, Ofri R, eds.  Slatter’s Fundamentals of Veterinary Ophthalmology. 4th ed. St. Louis, MO: Elsevier; 2008:433-434.


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