JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

August 2017

P-B16

 

Signalment (JPC #4081936-02):  domestic brown (fancy) rat

HISTORY:  This 13-month-old female domestic brown (fancy) pet rat presented for acute weight loss, lethargy, behavioral change, and hair loss.  At clinical presentation, the rat was dull but responsive and tachycardic.

HISTOPATHOLOGIC DESCRIPTION:  Lung (2 sections):  Affecting 40-50% of the two lung sections, bronchioles are markedly ectatic (bronchiectasis), compressing adjacent parenchyma.  Bronchiolar lumens are variably occluded by an exudate composed of basophilic to eosinophilic cellular and karryorhectic necrotic debris, mineral, and inflammatory cells composed of viable and degenerate neutrophils, fewer large foamy macrophages, multinucleate giant cells (foreign body and Langhans type), lymphocytes, plasma cells, and mucin.  This exudate often extends thorough the bronchiolar wall, infiltrating the peribronchiolar connective tissue and filling adjacent alveoli. Multifocally, bronchioles exhibit one or more of the following changes: discontinuous walls with loss or sloughing of the bronchiolar epithelium; attenuation with loss of cilia; or hyperplasia, piling up to 5 cell layers deep with goblet cell hyperplasia, and rare mitoses (regeneration). Multifocally, bronchiolar cilia are colonized by numerous lightly basophilic filamentous (0.5 x 8 um) bacilli.  There are peribronchiolar and perivascular infiltrates of lymphocytes, plasma cells (mild BALT hyperplasia), and fewer foamy macrophages that often contain brown globular to granular pigment (hemosiderin). Multifocally within adjacent, less affected alveoli, there is a pale eosinophilic homogenous fluid (edema) admixed with increased numbers of foamy alveolar macrophages.  Multifocally, alveolar septa are mildly expanded by edema and few macrophages.  There is multifocal alveolar emphysema.

Warthin-Starry stain:  There is heavy colonization of the ciliary borders of bronchiolar epithelial cells by slender, filamentous, argyrophilic bacteria that are 0.5 X 8 microns and are usually arranged parallel to the cilia.

MORPHOLOGIC DIAGNOSIS:  Lung:  Bronchopneumonia, necrosuppurative and lymphohistiocytic, chronic-active, multifocal to coalescing, moderate, with bronchiectasis, mineral, bronchiolar associated lymphoid hyperplasia, and many filamentous argyrophilic cilia-associated respiratory bacilli, domestic brown (fancy) rat, rodent.

ETIOLOGIC DIAGNOSIS:  Cilia‚ÄĎassociated respiratory (CAR) bacillary bronchopneumonia

CAUSE:  CAR bacillus

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURAL FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

 COMPARATIVE PATHOLOGY:

References:

  1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents & Rabbits, 4th ed. Ames, IA: Blackwell Publishing Ltd; 2016:61, 63, 125, 133-134, 201, 272-273.
  2. Bergottini R, Mattiello S, Crippa L, Scanziani E. Cilia-associated respiratory (CAR) bacillus infection in adult red deer, chamois, and roe deer. J Wildl Dis 2005;41:459-462.
  3. Caswell JL, Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. Philadelphia, PA: Elsevier; 2015:547.
  4. Fox JG, Anderson LC, Otto GM, Pritchett-Corning KR, Whary MT. Laboratory Animal Medicine. 3rd ed. San Diego, CA: Academic Press; 2015:102-104, 173-74.
  5. Rothenburger JL, Himsworth CG, Clifford CB, Ellis J, Treuting PM, Leighton FA. Respiratory pathology and pathogens in wild urban rats (Rattus norvegicus and Rattus rattus). Vet Pathol. 2015;52(6):1210-1219.
  6. Schoeb TR, Lindsay JR.  Cilia associated respiratory bacillus infection, rat, mouse, and rabbit.  In: Jones T, Dungworth D, Mohr U, eds. Respiratory System: Monographs on Pathology of Laboratory Animals. 2nd ed. Berlin, Germany: Springer-Verlag; 1996:117-126.


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