Signalment:  

Tissues from a 2.5 year old Hereford cow (Bos taurus)Patient presented with a 6-8 month duration of upper respiratory noise and a 2 week history of bloody nasal discharge. Physical examination reveals normal temperature and pulse, increased respiration, inspiratory stridor with multiple 0.5-2.0cm in diameter, tan firm sessile to polypoid masses present in both nares (Fig 1).

Gross Description:  

The patient is in excellent nutritional condition. Significant gross findings were limited to the nasal mucosa. The nasal mucosa of the bilateral nasal passages were expanded by multifocal and coalescing, raised, 0.5cm-2.0cm in diameter, granular to smooth, firm nodules that are present beginning 3cm caudal to the opening of the nares extending 15cm back into the nasal passage.

Morphologic Diagnosis:  

Granulomatous rhinitis, multifocal, severe with intralesional fungal organisms identified at culture as Pseudoallescheria boydii.

Lab Results:  

Fungal culture of gross lesions: Pseudoallescheria boydii
Bacterial culture of gross lesions: Small number of contaminants (Streptococcus sp., Bacillus sp.)
BVD immunohistochemistry (ear notch): negative

Condition:  

Pseudoallescheria boydii

Contributor Comment:  

In March to April of 2003, several individual cattle from geographically isolated herds across the state of Oklahoma presented with nearly identical clinical signs and gross lesions consistent with nasal granulomas. Cultures from the lesions revealed either Pseudoallescheria boydii or Bipolaris sp. Interestingly, similar fungal organisms were incidentally present within an ear notch skin sample (granulomatous dermatitis) obtained for BVD immunohistochemistry in this patient. 
Although uncommon, Pseudoallescheria boydii typically causes localized infections in cutaneous and subcutaneous connective tissues. Within lesions, the organism is often arranged as densely entangled hyphae (2-5_m) and swollen cells (15-25 _m) that can be grossly evident as tissue grains or granules. Within the nasal mucosa of this cow, the organisms were disseminated, and even when visualized with silver stains, did not form entangled hyphae. In fact, hyphae were inconspicuous compared to the variably-sized spherical swollen cells. 

Other than the cutaneous and subcutaneous mycetomas, Pseudoallescheria boydii has also been implicated in bovine abortions.

JPC Diagnosis:  

Nasal mucosa: Rhinitis, eosinophilic and granulomatous, diffuse, severe, with numerous fungal conidia and few hyphae, Hereford (Bos Taurus), bovine.

Conference Comment:  

This case, as published in the November 2007 issue of Veterinary Pathology, gives a good overview of Pseudoallescheria boydii.⁹ P. boydii are 5-8um septate hyphae that form 6-30um terminal round conidia with a discrete outer wall. They may exhibit narrow- or broad-based budding. GMS is preferred over PAS for demonstrating the hyphae and conidia. The case presented in conference is unusual in that it consists of numerous 6-30um round, occasionally budding conidia, with relatively few hyphae. In some slides, the conidia are light brown in H&E sections. 

P. boydii are ubiquitous within the environment. However, infections by this fungus are extremely rare and primarily reported in immunocompromised patients. In this case, there was no evidence the cow was immunocompromised. In animals, P. boydii primarily causes trauma-induced eumycotic mycetomas. It has rarely been associated with equine and bovine abortions, pneumonia in a calf, granulomatous rhinitis and onychomycosis in the horse, and eumycotic mycetoma and keratomycosis in the dog and horse. Unlike in dogs, nasal infections of cattle with P. boydii do not typically invade the underlying bone. 

Gross differentials for rhinitis in cattle include atopic rhinitis, neoplasia (e.g. lymphoma, squamous cell carcinoma), foreign body, actinobacilloisis, actinomycosis, and other fungal diseases (e.g. rhinosporidiosis, aspergillosis and phycomycosis). P. boydii differs from Aspergillus and Fusarium sp. by an absence of both angioinvasion and dichotomous branching.

Treatment of P. boydii is difficult and requires antifungal-susceptibility testing since the organism exhibits some level of inherent resistance to most antifungal agents.

References:

1. Chandler FW, Watts JC: Pathologic Diagnosis of Fungal Infections, pp. 75-79, 251-256. American Society of Clinical Pathologists, Chicago, IL, 1987
2. Hargis AM, Ginn PE: The integument. In: Pathologic Basis of Veterinary Disease, eds. McGavin MD, Zachary JF, 4th ed., pp. 1194-1195. Mosby Elsevier, St. Louis, Missouri, 2007
3. Knudtson WU, Kirkbride CA: Fungi associated with bovine abortion in the northern plains states (USA). J Vet Diagn Invest 4:181-185, 1992
4. Kwon-Chung KJ, Bennett JE: Pseudallescheriasis and Scedosporium infection. In: Medical Mycology, pp. 678-694. Lea & Febiger, Malvern, PA, 1992
5. Larone DH: Medically Important Fungi: A Guide to Identification, 4th ed., pp. 196-197. ASM Press, Washington, DC, 2002
6. Rippon JW: Medical Mycology: The Pathogenic Fungi and the Pathogenic Actinomycetes, 3rd ed., pp. 651-677. W. B. Saunders Company, Philadelphia, PA, 1988
7. Schlafer DH, Miller RB: Female genital system. In: Jubb, Kennedy, and Palmers Pathology of Domestic Animals, ed. Maxie MG, 5th ed., vol. 3, pp. 508-509. Elsevier Limited, St. Louis, MO, 2007
8. Schwartz DA: Pseudallescheriasis and Scedosporiasis. In: Pathology of Infectious Diseases, eds. Connor DH, Chandler FW, Schwartz DA, Manz HJ, Lack EE, vol. 2, pp. 1073-1079. Appleton & Lange, Stamford, CT, 1997
9. Singh K, Boileau MJ, Streeter RN, Welsh RD, Meier WA, Ritchey JW: Granulomatous and eosinophilic rhinitis in a cow caused by Pseudallescheria boydii species complex (anamorph Scedosporium apisospermum). Vet Path 44:917-920, 2007

A virtual slide is not available for this case.

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Fig 1

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