Systemic Rasamsonia piperina infection in a German shepherd cross dog

Disseminated Rasamsonia argillacea complex infection presenting as intraventricular brain hemorrhage in a German shepherd dog in Australia

A German Shepherd Dog diagnosed with Rasamsonia argillacea based on fungal culture and DNA sequencing, is the first documented case in Australia, and the Southern Hemisphere. This species is part of R. argillacea complex, which is an emerging concern in immunocompromised human and veterinary patients. Intraventricular brain hemorrhage, noted on MRI, has not been reported previously in a dog with fungal encephalitis. The patient was euthanized due to progression of clinical signs before a final diagnosis was made, so no treatment was attempted in this case.

Disseminated Rasamsonia argillacea infection in a dog

CASE HISTORY

A 4-year-old, male neutered Borzoi presented for unlocalised pain and frequent episodes of vocalisation.

CLINICAL FINDINGS

Pain was localised to the lumbar spine and radiographs revealed a L3-L4 lesion consistent with discospondylitis. The dog was treated for presumptive bacterial discospondylitis with surgical debridement, spinal stabilisation, and cephalexin. Samples collected from the affected intervertebral disc at the time of surgery revealed lymphoplasmacytic inflammation with no causative agent identified on histopathology or bacterial culture. After an initial period of improvement, signs recurred despite an 8-week antibiotic course, with the development of inappetence, weight loss, polydipsia, and polyuria. Repeat radiographs revealed a new cervical intervertebral lesion, and concurrent pyelonephritis was diagnosed based on blood and urine results. Fungal culture of urine resulted in growth of Rasamsonia argillacea species complex and disseminated fungal disease was clinically diagnosed. Antifungal treatment was commenced, however the dog deteriorated, and euthanasia was performed.

PATHOLOGICAL FINDINGS

Multifocal white plaques were grossly visualised in the spleen, mesenteric lymph nodes, cervical vertebrae, and kidneys. Periodic acid-Schiff-positive, fine, parallel-walled, occasionally branching, septate hyphae 5-10 μm in diameter, and conidia 5-7 μm in diameter were found on sectioning all organs. R. argillacea species complex was identified by fungal culture of urine and was considered the species of fungal organism seen histologically. The isolate was subsequently confirmed as R. argillacea by DNA sequencing.

DIAGNOSIS

Disseminated Rasamsonia argillacea infection.

CLINICAL RELEVANCE

Rasamsonia argillacea species complex is a recognised invasive mycosis in veterinary medicine, with disseminated disease causing significant clinical complications and death. This is believed to be the first report of infection caused by R. argillacea in a dog in Australasia and highlights the importance of awareness of a potential fungal aetiology in dogs with discospondylitis.Abbreviations: CLSI: Clinical and Laboratory Standards Institute; CRI: Constant rate infusion; MEC: Minimum effective concentration; MIC: Minimum inhibitory concentration; PAS: Periodic acid-Schiff.

Disseminated Rasamsonia argillacea species complex infections in 8 dogs

Background

Clinical features, treatment, and outcome of opportunistic infections with Rasamsonia spp., a nonpigmented filamentous mold, are not well documented in dogs.

Objectives

Describe clinical, radiographic, pathologic features, and outcome of dogs with disseminated Rasamsonia species complex infections.

Animals

Eight client‐owned dogs.

Methods

Retrospective case series. Medical records were reviewed to describe signalment, history, clinicopathologic and imaging findings, microbiologic and immunologic results, cyto‐ and histopathologic diagnoses, treatment, and outcome.

Results

Presenting complaints were nonspecific with anorexia (n = 5) and back pain (n = 4) most common. Five dogs were German Shepherd dogs. Six dogs had multifocal discospondylitis and 2 had pleural effusion. Six dogs had Rasamsonia piperina and 2 had Rasamsonia argillacea infections with isolates identified using DNA sequencing. Rasamsonia spp. were isolated by urine culture in 5 of 7 dogs. Five of 6 dogs had positive serum Aspergillus galactomannan antigen enzyme immunoassay (EIA) results. Median survival time was 82 days, and 317 days for dogs that survived to discharge. Four died during initial hospitalization (median survival, 6 days). All isolates had low minimum effective concentrations (MECs) to echinocandins with variable minimum inhibitory concentrations (MICs) for azole antifungal drugs.

Conclusions and Clinical Importance

Rasamsonia spp. infections in dogs are associated with multisystemic disease involving the vertebral column, central nervous system, kidneys, spleen, lymph nodes, lungs, and heart. The infection shares clinical features with other systemic mold infections and can be misidentified when using phenotypical microbiologic methods. Molecular techniques are required to identify the organism and guide appropriate antifungal treatment.