Introduction

• Systemic mycotic infection.
• Etiological agent:dimorphic fungusBlastomyces dermatitidis Blastomyces dermatitidis.
• Signs of infection:respiratory system, eyes, skin, lymph nodes, and bone.
• Route of infection:inhalation.
• Diagnosis:characteristic pulmonary changes in a young, large breed, male dog.
• Identification:in cytological or histopathological samples.
• Treatment:Itraconazole and other antifungal agents.
• Prognosis:Good to fair.

Pathogenesis

Etiology

• Blastomyces dermatitidis Blastomyces dermatitidis.

Predisposing factors

• Exposure to a common source in an endemic area.
• Large-breed, young male dogs (1-5 years of age; most common age = 2 years).
• Subclinical infection may occur, and immune-compromise of the animal may predispose to the development of clinical disease.

Pathophysiology

• The dimorphic yeast organism usually gains entry into the body via inhalation.
• Organism converts into a yeast form at body temperature.
• Infection first develops in the lungs, then disseminates via hematogenous and lymphatic routes to the rest of body. Specific target organs include the eyes, bone, brain, skin, soft tissues, lymph nodes and testes.

• Organisms cause a pulmonary infection.
• Immune system mounts response to clear infection, with variable success.
• Host immune system failure -> generalized infection -> host death.

Timecourse

• Incubation time -> 5-12 weeks.

Epidemiology

• Exists in concentrated areas within endemic areas.
• Several dogs in a neighborhood or household may be affected.
• Dogs are more susceptible to infection, so may be considered a sentinel for human infection.

Diagnosis

Treatment

Prevention

Outcomes