Disseminated Penicillium labradoris (synonym: P. labradorum) in three dogs from Western Australia

This case series presents three new cases of disseminated Penicillium labradoris (syn. P. labradorum) infection in unrelated dogs from Western Australia, illustrating varied clinical presentations and outcomes. P. labradoris infections are rare in dogs, with only three prior cases reported worldwide. Typically considered low-virulence mycotic pathogens, Penicillium species can occasionally cause severe disease in dogs likely affected by some genetically programmed immune defect.

Case one was a three-year-old Staffordshire bull terrier crossbreed who presented for lameness, metatarsal swelling and lymphadenomegaly. Radiographs showed osteomyelitis and P. labradoris was cultured from both bone and lymph node biopsy specimens. Treatment included en bloc metatarsal excision and long-term antifungal therapy, initially with voriconazole and terbinafine, and subsequently delayed-release posaconazole. Currently, 1217 days post-diagnosis, the dog remains clinically well with only mild biomarker elevations. The second case featured bilateral asymmetrical forelimb fungal osteomyelitis with more severe left forelimb involvement and demonstrated a good clinical response to delayed-release posaconazole and terbinafine. The third case presented with severe disseminated infection affecting multiple organ systems, including lymphadenomegaly, gastrointestinal and pulmonary involvement, and tri-cavitary effusion. Despite treatment with posaconazole, terbinafine, and voriconazole, the dog succumbed.

This series underscores the variability of P. labradoris presentations in dogs and highlights potential for successful long-term management with posaconazole therapy. Serial biomarker determinations and therapeutic drug monitoring play a crucial role in guiding treatment. These cases suggest intriguing aspects of pathogen virulence and potential genetic susceptibility in individual unrelated dogs. Although this fungal species is present in the US, France, and Brazil, it is of great interest that all three Australian cases were from Perth, Western Australia.