Systemic (mainly pulmonary) mycoses caused by Paecilomyces spp have been described in humans and various other animals, especially those with lowered body temperatures. Infection in captive reptiles and amphibians is probably fairly common; other hosts include dogs, horses, cats (nasal granuloma), and goats (mastitis). More significant causal fungi are P lilacinus and P variotii. The fungi, usually considered nonpathogenic, are widely distributed in soil and decaying organic matter. Infection usually has been secondary to debilitation, immunosuppression, and/or alteration of normal microbial flora by prolonged administration of antibiotics.

Clinical Findings and Lesions

Signs vary and are not specific but may reflect tissue or organ involvement. Involved organs are enlarged and contain raised, gray-white nodules. Granulomatous lesions (multiple, pale foci) that contain septate pseudohyphae (2–3 μm in diameter), oval conidia, and spherical to oval, thin-walled spores (3–6 μm) are found in many tissues (eg, lungs) in disseminated cases and are closely associated with small and medium-sized arterioles.

Diagnosis

The gross lesions can be confused with those of other systemic mycoses. However, the septate hyphae, conidia, and spores of this fungus differ from common pathogenic fungi such as Aspergillus spp and those of mucormycosis. Diagnosis can be made by cultural isolation of the fungus from multiple specimens of lesions. With most species, growth may be absent or restricted at 37°C but good at 5–30°C.

Treatment

No treatment regimens have been described. Paecilomyces spp vary greatly in sensitivity to antifungal agents; P lilacinus appears highly resistant to amphotericin B and flucytosine but sensitive to ketoconazole, while P variotii is sensitive to the first 2 drugs.

Last full review/revision March 2012 by Joseph Taboada, DVM, DACVIM