Blastomyces spp

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Nodular nasal blastomycosis in a dog[1]
Blastomyces dermatitidis osteomyelitis in the proximal tibia of a dog[2]

Blastomyces are a soil-dwelling saprophytic and zoonotic dimorphic fungus which sometimes causes blastomycosis, a severe, commonly fatal infection in dogs that live in the United States, Canada, and parts of Africa[3].

The fungus is presumably inhaled from infected soil into the lungs of a susceptible animal, initially causing a pneumonia. In dogs, the fungus often disseminates from the lungs to the skin, eyes, lymph nodes, and bones[4]. The mortality rate exceeds 90% for dogs that do not receive prompt antifungal treatment[5].

Co-infections with other fungi are common, such as Pythium insidiosum[6].

In rare cases, often immunocompromised dogs, it can cause systemic illness.

Species which are pathogenic to dogs include:

  • Blastomyces dermatitidis[7]

Clinically affected dogs often present with fever, subcutaneous nodules[8], rhinitis, gastroenteritis, pneumonia, lymphadenitis, mastitis, prostatitis[9] or endophthalmitis[10].

Diagnosis is based on cytologic evaluation, histologic examination with special stains, and immunohistochemical analysis of tissues collected antemortem or at necropsy[11].

Treatment can be difficult due to the systemic spread and slow-growing nature of this mycosis. Drugs such as amphotericin B, itraconazole, ketoconazole or turbinafine[12] for 4 - 6 months are empirically recommended[13].

Prognosis is guarded in most cases, although recently a live-attenuated vaccine has been developed which shows promise[14].

References

  1. Dog Health Guide
  2. University of Pennsylvania
  3. Herrmann JA et al (2011) Temporal and spatial distribution of blastomycosis cases among humans and dogs in Illinois (2001-2007). J Am Vet Med Assoc 239(3):335-343
  4. Wüthrich M et al (2011) Safety, tolerability, and immunogenicity of a recombinant, genetically engineered, live-attenuated vaccine against canine blastomycosis. Clin Vaccine Immunol 18(5):783-789
  5. Legendre AM (2006) Blastomycosis. Saunders Elsevier, St. Louis, MO
  6. Connolly SL et al (2012) Dual infection with Pythium insidiosum and Blastomyces dermatitidis in a dog. Vet Clin Pathol 41(3):419-423
  7. Anderson JL et al (2013) Clinical and molecular epidemiology of veterinary blastomycosis in Wisconsin. BMC Vet Res 9(1):84
  8. Bulla C & Thomas JS (2009) What is your diagnosis? Subcutaneous mass fluid from a febrile dog. Vet Clin Pathol 38(3):403-405
  9. Reed LT et al (2010) Pathology in practice. Granulomatous pneumonia, prostatitis and uveitis with intralesional yeasts consistent with Blastomyces. J Am Vet Med Assoc 236(4):411-413
  10. Ditmyer H & Craig L (2011) Mycotic mastitis in three dogs due to Blastomyces dermatitidis. J Am Anim Hosp Assoc 47(5):356-358
  11. Greene JP et al (2012) What is your diagnosis? Infection with dimorphic Blastomyces dermatitidis. J Am Vet Med Assoc 240(8):945-946
  12. Sakai MR et al (2011) Terbinafine pharmacokinetics after single dose oral administration in the dog. Vet Dermatol 22(6):528-534
  13. Totten AK et al (2011) Blastomyces dermatitidis prostatic and testicular infection in eight dogs (1992-2005). J Am Anim Hosp Assoc 47(6):413-418
  14. Wüthrich M et al (2011) Safety, tolerability, and immunogenicity of a recombinant, genetically engineered, live-attenuated vaccine against canine blastomycosis. Clin Vaccine Immunol 18(5):783-789