Introduction

Classification

Taxonomy

• Dimorphic fungus.

Active Forms

Clinical Effects

Epidemiology

Habitat

• There is limited evidence of natural reservoirs of Blastomyces.
• Soil saprophyte, but attempts to isolate the organism from soil have been inconsistent.
• Colonizes animal wastes and decaying vegetation at low pH and in moist conditions.

Lifecycle

• Yeast form is found in tissues → reproduces by broad-based budding.
• Yeast form occurs in soil and when grown at room temperature → reproduces asexually using conidia.
• Also has a sexual stage, Ajellomyces dermatitidis.

Transmission

• Most commonly by inhalation.
• Rarely percutaneous transmission from a bite.

Pathological effects

• Impaired cell-mediated immunity predisposes to the infection and may be the result of the infection.
• Both cell-mediated and humoral responses occur.

• Entry of conidia occurs, usually via the respiratory tract.
• Change to yeast form occurs in the tissues.
• Inflammatory response occurs resulting in pyogranulomatous lesions in the terminal bronchioles and lymph nodes.
• Dissemination may occur to:
  • Bones.
  • Bone marrow.
  • Eyes.
  • Skin.
  • Urogenital tract.
  • Mammary glands.
• Animal usually presents with:
  • Skin or respiratory signs.
  • Fever.
  • Anorexia.
  • Weight loss.
  • Ocular disease.
  • Locomotor disturbances.
• Rarely central nervous system signs.

Control

Control via chemotherapies

• Amphotericin B Amphotericin B (drug of choice in immunocompromised hosts), ketoconazole Ketoconazole and itraconazole Itraconazole.

Vaccination

• Not available.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Baumgardner D J & Paretsky D P (1999) The in vitro isolation of Blastomyces dermatitidis from a woodpile in north central Wisconsin, USA. Med Mycol 37 (3), 163-168 PubMed.
• Giles S, Klein B & Czuprynski C (1999) The effect of canine macrophages on the adherence and growth of Blastomyces dermatitidis yeast - evidence of a soluble factor that enhances the growth of B. dermatitidis yeast. Microbiol Pathog 27 (6), 395-405 PubMed.
• Arceneaux K A, Taboada J & Hosgood G (1998) Blastomycosis in dogs: 115 cases (1980-1995). JAVMA 213 (5), 658-664 PubMed.
• Côté E, Barr S C & Allen C (1997) Possible transmission of Blastomycosis dermatitidis via culture specimen. JAVMA 210 (4), 479-480 PubMed.
• Bloom J D, Hamor R E, Gerding P A Jr. (1996) Ocular blastomycosis in dogs: 73 cases, 108 eyes (1985-1993). JAVMA 209 (7), 1271-1274 PubMed.
• Kraweic D R, McKiernan B C, Twardock A R et al (1996) Use of an amphotericin B lipid complex for the treatment of blastomycosis in dogs. JAVMA 209 (12), 2073-5 PubMed.
• Legendre A M, Rohrbach B W, Toal R L et al (1996) Treatment of blastomycosis with itraconazole in 112 dogs. J Vet Intern Med 10 (6), 365-71 PubMed.
• Rudmann D G, Coolman B R, Perez C M et al (1992) Evaluation of risk factors for blastomycosis in dogs: 857 cases (1980-1990)​. JAVMA 201 (11), 1754-1759 PubMed.
• Hawkins E C & DeNicola D B (1990) Cytologic analysis of tracheal wash specimens and bronchoalveolar lavage fluid in the diagnosis of mycotic infections in dogs. JAVMA 197 (1), 79-83 PubMed.