Disseminated Pneumocystosis in a Toy Poodle

Area of Science:

• Veterinary Pathology
• Mycology
• Canine Infectious Diseases

Background:

• Pneumocystis pneumonia (PCP) is a severe opportunistic infection.
• Disseminated PCP is rare in immunocompetent hosts, including dogs.
• Toy poodles may be predisposed to certain conditions.

Observation:

• A 1.5-year-old male toy poodle presented with respiratory distress, weight loss, and melena.
• Thoracic radiography revealed an interstitial lung pattern.
• Necropsy showed disseminated Pneumocystis carinii infection in multiple organs.

Findings:

• Pneumocystis carinii organisms were identified in lungs, lymph nodes, liver, heart, kidneys, spleen, GI tract, and pancreas.
• Calcified foci containing P. carinii were observed in the lungs.
• Evidence of lymphogenous spread was noted in non-thoracic lymph nodes.
• Diagnostic confirmation utilized Grocott methenamine silver staining, immunohistochemistry (IHC), and PCR for P. carinii.

Implications:

• This case demonstrates disseminated pneumocystosis in a dog.
• Immunohistochemistry confirmed depletion of IgA and IgG, suggesting an underlying immunodeficiency.
• Accurate diagnosis requires advanced histopathological and molecular techniques.