Aspergillus spp

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Discospondylitis of the sternal vertebrae as a result of Aspergillus versicolor[1]
Endoscopic view of a sinonasal tumor developing subsequent to nasal aspergillosis in a dog[2]

Aspergillus spp are a commensal filamentous fungus found as part of the normal skin flora of dogs worldwide.

Their pathogenic role may be related to host immune system as well the fungus virulence factors such as aflatoxin B1 and ochratoxins A and B[3] which contaminates cereals and causes aflatoxicosis.

Systemic dissemination of the organism is common, and the German Shepherd appears predisposed to Aspergillus-induced meningoencephalitis due to an inappropriate mucosal IgA response[4].

Species which are pathogenic to dogs include:

  • Aspergillus fumigatus[5]
  • Aspergillus versicolor
  • Aspergillus terreus
  • Aspergillus deflectus (Neosartorya fischeri)[6]
  • Aspergillus ochraceus[7]

This dermatophyte primarily causes dermal disease such as otitis externa or paronychia[8].

In immunocompromised dogs, systemic disease may occur, such as sinusitis, rhinitis[9], bronchopneumonia[10]discospondylitis, osteomyelitis, pyelonephritis and pyometra[11] have occurred in dogs.

A correlation between chronic inflammation and sequential development of tumors has to be considered, especially with nasal aspergillosis, as the risk of developing nasal granulomas is relatively high.

Diagnosis is based on clinical presentation and culture of the fungus in the laboratory. The fungus usually stains positively with periodic acid-Schiff and Grocott stains[12]. Sensitive ELISA and PCR assays are available for establishing a definitive diagnosis[13].

A differential diagnosis would include phaeohyphomycosis and lymphoma.

Parenteral treatment is usually required with systemic involvement.

Itraconazole[14] is the drug of choice, given for 5 - 6 months to effect elimination of fungal spores, but other drugs such as ketoconazole, itraconazole and enilconazole have also been trialed in dogs both parenterally and topically[15].

Topical treatment with clotrimazole gel has also shown benefit in some cases, when applied intranasally[15].

In dogs with localized pulmonary cavitations, a lobectomy is usually indicated[16].

References

  1. Zhang S et al (2012) Aspergillus versicolor, a new causative agent of canine disseminated aspergillosis. J Clin Microbiol 50(1):187-191
  2. Greci V et al (2009) Sinonasal tumor in 3 dogs after successful topical treatment for frontal sinus aspergillosis. Can Vet J 50(11):1191-1194
  3. Dirheimer G & Creppy EE (1991) Mechanism of action of ochratoxin A. IARC Sci Publ 115:171-186
  4. Day MJ (1996) Low IgA concentration in the tears of German Shepherd Dogs. Aust Vet J 74:433–434
  5. Anagnostou TL et al (2012) Anesthesia and perioperative management of a pneumonectomized dog. J Am Anim Hosp Assoc 48(2):145-149
  6. Krockenberger MB et al (2011) Sequential opportunistic infections in two German Shepherd dogs. Aust Vet J 89(1-2):9-14
  7. Ghibaudo G & Peano A (2010) Chronic monolateral otomycosis in a dog caused by Aspergillus ochraceus. Vet Dermatol 21(5):522-526
  8. Coyner K (2010) Otomycosis due to Aspergillus spp. in a dog: case report and literature review. Vet Dermatol 21(6):613-618
  9. Vanherberghen M et al (2012) Analysis of gene expression in canine sino-nasal aspergillosis and idiopathic lymphoplasmacytic rhinitis: a transcriptomic analysis. Vet Microbiol 157(1-2):143-151
  10. Jones BG & Pollard RE (2012) Relationship between radiographic evidence of tracheobronchial lymph node enlargement and definitive or presumptive diagnosis. Vet Radiol Ultrasound 53(5):486-491
  11. Walker JT et al' (2012) A novel case of canine disseminated aspergillosis following mating. Can Vet J 53(2):190-192
  12. Adamama-Moraitou KK et al (2011) Aspergillus fumigatus Bronchopneumonia in a Hellenic Shepherd Dog. J Am Anim Hosp Assoc 47(2):e13-18
  13. Garcia RS et al (2012) Sensitivity and specificity of a blood and urine galactomannan antigen assay for diagnosis of systemic aspergillosis in dogs. J Vet Intern Med 26(4):911-919
  14. Cafarchia C et al (2012) In vitro antifungal susceptibility of Malassezia pachydermatis from dogs with and without skin lesions. Vet Microbiol 155(2-4):395-398
  15. 15.0 15.1 Sharman M et al (2012) Clotrimazole and enilconazole distribution within the frontal sinuses and nasal cavity of nine dogs with sinonasal aspergillosis. J Small Anim Pract 53(3):161-167
  16. Kulendra E et al (2010) Cavitary pulmonary lesion associated with Aspergillus fumigatus infection in a German shepherd dog. J Small Anim Pract 51(5):271-274