JPC SYSTEMIC PATHOLOGY
SPECIAL SENSES
April 2018
S-M03 (NP)

Signalment (JPC #4002461):  5-year-old female spayed Rhodesian ridgeback, canine

HISTORY: The dog was presented for a large (approximately 7 cm diameter), subcutaneous moveable mass over the left shoulder. Two weeks after surgical excision, the dog presented with neurologic signs and blindness. Euthanasia was elected because of poor prognosis.

HISTOPATHOLOGIC DESCRIPTION:  Eye:  Within the vitreous chamber, elevating the detached retina and multifocally extending into the subjacent choroid is a dense cellular exudate of many viable and degenerate neutrophils and macrophages admixed with eosinophilic cellular and karyorrhectic debris (necrosis), fibrin, eosinophilic globular protein, and minimal hemorrhage and mineral.  Both free within the exudate as well as within macrophages are many round algae sporangia which are 10-20 um in diameter with a 2-3 um thick amphophilic cell wall and a basophilic nucleus.  Many algae undergo endosporulation characterized by wedge-shaped, radially arranged, angular endospores (daughter cells) divided by septations filling the sporangia.  The detached retina is thickened by fibrin, hemorrhage and edema and multifocally few vessel walls within the retina are expanded by few neutrophils, brightly eosinophilic protein, cellular debris (vasculitis) and are surrounded by few lymphocytes and histiocytes.  There is marked asymmetrical necrosis and loss of varying layers of the retina, most prominently adjacent to areas of exudate.  There is moderate hyperplasia and hypertrophy of the retinal pigment epithelium.  The choroid and clilary body are multifocally infiltrated and/or expanded by few to many neutrophils, macrophages, lymphocytes, plasma cells, congested vessels and dilated lymphatics.  Multifocally within the sclera, lymphatics are dilated and filled with edema and mild hemorrhage and inflammatory cells.

MORPHOLOGIC DIAGNOSIS:  Eye:  Endophthalmitis, pyogranulomatous, diffuse, moderate, with retinal detachment and necrosis, and numerous extracellular and intrahistiocytic endosporulating algae, Rhodesian ridgeback, canine.

ETIOLOGIC DIAGNOSIS:  Ocular protothecosis

CAUSE:  Prototheca zopfii

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

Dogs: 

Cats: 

Cattle: 

TYPICAL GROSS FINDINGS:

Dogs: 

Cats:

Cattle: 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

Dogs: 

Cats: 

Cattle: 

Histomorphology of Algae:

ULTRASTRUCTURAL FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Cheville NF. Algae, fungi, and other eukaryotes. In: Cheville NF, ed. Ultrastructural Pathology The Comparative Cellular Basis of Diseases. 2nd ed. Ames, IA:  Wiley Blackwell; 2009:573-575.
  2. Gelatt KN, Plummer CE. Color Atlas of Veterinary Ophthalmology. 2nd ed. Chichester, UK: John Wiley & Sons, Inc; 2017.359.
  3. Huth N, et al. Prototheca zopfii genotype 2-induced nasal dermatitis in a cat. J Comp Path. 2015;152:287-290.
  4. Lane LV, Meinkoth JH, Brunker J, et al. Disseminated protothecosis diagnosed by evaluation of CSF in a dog. Vet Clin Pathol. 2012;41(1):147-52.
  5. Macedo JTSA, Riet-Correa F, Dantas AFM, Simoes SVD. Cutaneous and nasal protothecosis in a goat. Vet Pathol. 2008;45:352-354.
  6. Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St. Louis, MO: Elsevier; 2016:665.
  7. Pressler BM. Protothecosis and Chlorellosis. In: Greene CE, ed. Infectious Diseases of the Dog and Cat. 4th ed. St. Louis, MO:Elsevier; 2012:696-701.
  8. Schöniger S, Roschanski N, Rösler U, Vidovic A, Nowak M, Dietz O, Wittenbrink MM, Schoon HA. Prototheca species and Pithomyces chartarum as causative agents of rhinitis and/or sinusitis in horses. J Comp Path. 2016;155:121-125.
  9. Uzal FA, Plattner BL, Hostetter JM. Alimentary system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:203-204.
  10. Wilcock BP, Njaa BL. Special senses. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, Vol 1. 6th ed. St. Louis, MO: Elsevier; 2016:451.


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