Entomophthoromycosis and mucormycosis are disease processes that were previously included under the now-obsolete heading "zygomycosis." These ubiquitous fungi are present in soil and decaying vegetation and, in the case of Basidiobolus spp, the GI tracts of amphibians, reptiles, and macropods. Conidiobolomycosis coronatus affects predominantly the mucosa of the nose and mouth. Basidiobolus infects the lateral aspects of the head, neck, and body.
Entomophthoromycosis and mucormycosis include infections due to Basidiobolus spp and Conidiobolus spp (order Entomophthorales) and isolated case reports of disease due to organisms in order Mucorales.
These organisms primarily cause infections of the nasopharyngeal mucosa and subcutaneous tissue of dogs, horses, and rarely other animals (llamas, sheep) by C coronatus, C incongruus, C lamprauges, or B ranarum.
Clinical Findings of Entomophthoromycosis and Mucormycosis in Animals
Ulcerative pyogranulomas of the mucous membranes of the nasopharynx or mouth, or nodular growths of the nasal mucosa and the lips that present as nonhealing wounds or draining tracts, may occur with conidiobolomycosis. These lesions may result in mechanical obstruction of the nasal cavity, dyspnea, and nasal discharge. Local dissemination into the retropharyngeal, retrobulbar, or other tissues of the face may be noted and may cause facial deformity.
Lesions of basidiobolomycosis are usually single, circular, ulcerative, pruritic nodules of the skin of the upper body. Fistulous tracts discharge a serosanguineous fluid from the lesions, which frequently are traumatized. Extension to regional lymph nodes results in swelling of the nodes and development of yellow necrotic foci. Lesions may contain a creamy, yellow central core of necrotic tissue.
Gastrointestinal disease similar to GI pythiosis has been reported with clinical signs of vomiting, diarrhea, and weight loss. Disseminated basidiobolomycosis is rare but has been described in dogs and a mandrill. Mucormycosis can affect the GI tract, cerebrum, and skin.
Lesions
In excised tissues or necropsy specimens, a thickened fibrotic dermis has scattered red or creamy white areas. The lesions, which contain hyphal forms, a heavy infiltrate of eosinophils, and sequestered areas of necrosis, have histologic features of infectious granulomas. The lesions are usually easy to differentiate histologically from pythiosis because the hyphae are larger (5–20 mcm), sparsely septate, and surrounded by a broad "sleeve" of eosinophilic material up to 25 mcm thick that makes the hyphae easy to see on H&E stain.
Diagnosis of Entomophthoromycosis and Mucormycosis in Animals
Straightforward histologic diagnosis
Culture and PCR assay required for definitive speciation
Clinically, entomophthoromycosis and mucormycosis may be confused with cutaneous habronemiasis and oomycosis but can be differentiated by microscopic examination of tissues as described above. Culture is required to specifically identify the causative fungus.
Treatment of Entomophthoromycosis and Mucormycosis in Animals
No definitive treatment protocols
Wide surgical resection followed by prolonged antifungal treatment for cutaneous infections
For nasopharyngeal or deep entomophthoromycosis and mucormycosis infections, itraconazole (10 mg/kg every 24 hours, PO) administration is recommended. Although lesions often regress, recurrence is common after treatment is discontinued, and treatment for 12–18 months is suggested. Cutaneous infections should be treated with wide surgical resection followed by longterm itraconazole.
Key Points
Entomophthoromycosis and mucormycosis are clinically indistinguishable from pythiosis and lagenidiosis.
Biopsy and histopathologic examination can confirm diagnosis.
Excision and prolonged antifungal treatment are recommended.
