Abstract

Mycotic diseases of marine mammals have been increasingly recognized. However, diagnosis of fungal disease continues to be a clinical challenge hampering initiation of adequate treatment. Increased awareness of the potential for involvement by a variety of mycotic agents in systemic marine mammal disease may improve the chances of detecting the organism and of successfully treating the disease.

A recently weaned male northern elephant seal (Mirounga angustirostris) pup that had stranded along the central California coast and had been undergoing rehabilitation was found severely obtunded and with marked hyponatremia and hypochloremia after a history of intermittent regurgitation. The animal was euthanatized after little response to therapy. Gross post mortem findings included multifocal abscessing affecting brain, spleen, kidney, muscle and subcutaneous tissue. Scedosporium apiospermum was cultured from brain, kidney and subcutaneous tissue along with Enterococcus sp., Providencia retgerii and Pseudomonas putida. Histopathologic examination revealed multiple, variably sized fungal granulomas in the kidneys, brain, liver and skeletal muscle. The distribution of the lesions in multiple organs and the pattern of lesions in the lungs indicates hematogenous spread of the fungus. The portal of fungal entry is not known. The lesions were acute, probably of less than 1 wk duration, and the necrotizing nature of the lesions and the accompanying vasculitis was consistent with a primary fungal infection. The mixed bacteria also obtained from culture were considered to be secondary or post mortem invaders.

S. apiospermum is the asexual state of the fungus Pseudallescheria boydii. The fungus has been isolated from a number of substrates including soil, sewage, polluted water, poultry and cattle manure, as well as materials from coastal tidelands such as algae. In humans, S. apiospermum has been shown to affect a variety of tissues including brain and bone in patients that are usually immunocompromised and also brain abscesses following aspiration of contaminated water during near drowning. In experimentally affected mice, the fungus was shown to have an affinity for kidney and brain causing abscesses and necrosis. It is unknown whether the fungus in the elephant seal was a primary pathogen or if it was secondary to immune compromise by an unknown factor. This seal had been treated with a variety of antibiotics, anthelmintics, and a short course of low dose (0.25 mg/kg) dexamethasone almost 3 mo prior to euthanasia. It is possible that the rehabilitation process may have resulted in chronic stress and depressed immune function. This is the first report of the isolation of Scedosporium apiospermum associated with lesions from a marine mammal. The current report underscores the importance of fungal organisms in marine mammal disease and strongly suggests that the marine mammal clinician not discount a fungal etiology when initiating treatment.