The ultrastructure of macrophages in granulomatous colitis of Boxer dogs

Area of Science:

• Veterinary Pathology
• Canine Infectious Diseases
• Microbiology

Background:

• Granulomatous colitis is a rare inflammatory bowel disease affecting Boxer dogs.
• The etiology of this condition remains largely unknown, prompting further investigation into potential causative agents.

Purpose of the Study:

• To characterize the ultrastructural contents of macrophages in Boxer dogs with granulomatous colitis.
• To identify potential infectious agents contributing to the pathogenesis of this disease.

Main Methods:

• Electron microscopy was utilized to examine tissue samples from thirteen Boxer dogs diagnosed with granulomatous colitis.
• Macrophages were analyzed for intracellular inclusions and the presence of microorganisms.

Main Results:

• Three types of macrophages were identified, with the most common containing residual bodies and phagosomes with granular spheres.
• Rare macrophages harbored bacteria, while others contained abundant coccoid to lobulated granular structures (100-500 nm) resembling chlamydia.
• Evidence suggested a transition from phagocytic particles to residual bodies within macrophages.

Conclusions:

• Granulomatous colitis in Boxer dogs is likely caused by a lipid-rich, ribosome-rich organism (100-500 nm) with characteristics of chlamydia.
• This organism possesses a cell membrane and occasionally a nucleoid, representing a potential novel pathogen in canine colitis.