Canis ISSN: 2398-2942

Blastomycosis

Contributor(s): Rosanna Marsella, Rhea Morgan

Introduction

  • Cause: a systemic mycotic infection caused by a dimorphic fungus Blastomyces dermatitidis Blastomyces dermatitidis.
  • Dogs are most commonly infected but cats, horses, and people may also develop systemic disease.
  • Signs: pulmonary signs, lameness, lymphadenopathy, ocular signs, skin lesions.
  • Diagnosis: serology, cytology, histology.
  • Treatment: prolonged itraconazole Itraconazole , other imidazoles, amphotericin B Amphotericin B.
  • Prognosis: good, unless brain involvement or severe pulmonary disease are present.

Pathogenesis

Etiology

Predisposing factors

General

  • Living in an endemic area.
  • Close proximity to shoreline has been reported as a risk factor.
  • Outdoor activity, eg hunting.

Pathophysiology

  • Infection occurs by inhalation of the spores present in the environment.
  • After the organism becomes established in the lung, dissemination occurs.
  • Cutaneous blastomycosis is usually a manifestation of disseminated disease.
  • Preferred sites in the dog are lungs (80%), eyes (40%), skin (20-40%), bones (30%), subcutaneous tissues, lymph nodes, brain, and testes.
  • Other organs that may become infected include the prostate, liver, mammary glands, and heart.
  • Seasonality has been reported in USA (higher number reported from late spring through late fall).
  • Blastomyces is dimorphic fungus that lives as a saprophytic (mycelial form) in sandy acid soil producing infective spores.
  • Once organism enters the host conversion from the spore into the yeast form occurs.
  • Direct inoculation in the skin is rare (focal cutaneous disease).
  • Dissemination is thought to occur via both hematogenous and lymphatic routes.

Timecourse

  • Incubation in the dog is thought to be 5 12 weeks.
  • A few dogs may show minimal signs for months until the disease suddenly progresses.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • 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.
  • Gortel K, McKiernan B C, Johnson J K & Campbell K L (1999) Calcinosis cutis associated with systemic blastomycosis in three dogs. JAAHA 35 (5), 368-374 PubMed.
  • Arceneaux K A, Taboada J & Hosgood G (1998) Blastomycosis in dogs - 115 cases (1980-1995). JAVMA 213 (5), 658-664 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.
  • Krawiec D R, McKiernan B C, Twardock A R, Swenson C E, Itkin R J, Johnson L R, Kurowsky L K & Marks C A (1996) Use of an amphotericin B lipid complex for treatment of blastomycosis in dogs. JAVMA 209 (12), 2073-2075 PubMed.
  • Legendre A M, Rohrbach B W, Toal R L, Rinaldi M G, Grace L L & Jones J B (1996) Treatment of blastomycosis with itraconazole in 112 dogs. J Vet Intern Med 10 (6), 365-371 PubMed.
  • Garma-Avina A (1995) Cytologic findings in 43 cases of blastomycosis diagnosed ante-mortem in naturally-infected dogs. Mycopathologia 131 (2), 87-91 PubMed.

Other sources of information

  • Legendre A M (1998) Blastomycosis. In: Green CE (ed): Infectious diseases of the Dog and Cat. 2nd Ed. W B Saunders, Philadelphia, pp 371-377.


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