In dogs, which organ is most frequently the primary site of blastomycosis?

Blastomycosis is a fungal infection caused by the organism Blastomyces dermatitidis, which is primarily associated with moist soil and decaying organic matter. In dogs, the most common primary site of infection is the lungs. This is due to the route of infection; when dogs inhale the fungal spores, they predominantly affect the respiratory system before potentially disseminating to other organs.

Infecting the lungs causes a range of respiratory symptoms and can lead to pneumonia or other pulmonary issues. While the fungus can spread to other organs such as the liver, spleen, or intestines, the initial and most frequent site of infection remains the lungs. The pathology and clinical presentation in dogs with blastomycosis typically center around respiratory signs, further emphasizing the lungs as the primary organ involved in this condition.