Abstract

An Atlantic bottlenose dolphin, Tursiops truncatus, collected in the Gulf of Mexico and maintained in Kaneohe Bay, Hawaii for eleven months, presented clinical signs of cellulitis and pneumonia prior to death. Response to antibiotic and antifungal therapy was unremarkable. A necropsy revealed granulomatous pneumonia and severe thoracic lymphadenitis. Fungal cells, morphologically and tinctorially compatible with Blastomyces dermatitidis, were found in the heart, lung, kidney, spleen, liver, lymph node, gastrointestinal tract, and skin. The diagnosis of systemic blastomycosis was established by specific immunofluorescent staining of the fungus in tissues and detection of specific serum precipitins by immunodiffusion tests.

The attending veterinarian, exposed to the diseased dolphin during treatment and necropsy, developed a pustular dermatitis two weeks after the animal's death. Cellulitis, lymphangitis, and lymphadenitis followed, and B. dermatitidis was cultured from a skin biopsy. Normal healing occurred without antifungal therapy.

Introduction

Blastomycosis is a granulomatous and suppurative disease of various animals and humans caused by the dimorphic fungus, Blastomyces dermatitidis. This organism is a soil inhabiting saprophyte which produces mycelia and conidia. The lungs are the primary focus of infection from the airborne conidia, and cutaneous or systemic disease may result from dissemination.(1-3) Primary cutaneous blastomycosis is rare but may follow subcutaneous inoculation of the fungus into humans and animals.(3-10) The disease is endemic in most of the eastern United States, especially in the Mississippi and Ohio River basin areas.(3, 10) Aside from humans, dogs are the most susceptible species, but the disease has also been reported in cats,(11-16) a horse,(17) a Steller's sea lion,(18) a ferret,(19) 6 lion,(20) and a deer.(21) A review of systemic mycoses in marine mammals included a case of blastomycosis in a dolphin; however, the anatomic location and severity of lesions were not mentioned.(22)

Case History

An adult female Atlantic bottlenose dolphin, Tursiops truncatus, presented clinical signs of cranial swelling, lethargy and anorexia one year after collection in the Mississippi Sound, Gulf of Mexico.

The initial clinical sign noted was a swelling, 5 cm in diameter, discolored and firm, located on the melon. Initial hematology results showed a leukocytosis (17,700/ul) with a slight left shift. Marked lymphopenia and eosinopenia were evident. Other blood parameters were considered normal.

The swelling was an abscess with sanguinopurulent exudate. The animal was treated both topically (antiseptic flushes) and systemically (oral antibiotics based on culture isolate-, of a Vibrio spp. and another gram-positive anaerobe. Normal healing of the open wound was complicated by cellulitis, but the total leukocyte number fell to 2,200/ul.

Improvement was noted in appetite, activity, and hematology (regenerative left shift and a return of lymphocytes, eosinophils, and monocytes) during the third week of treatment. However, a diphtheritic membrane from which a Candida sp. was subsequently cultured was seen in the mucosal lining of the blow hole. Despite the addition of an antifungal agent (Ketoconazole) to the treatment regimen. Dyspnea and anorexia progressed until the animal died four weeks after the onset of initial symptoms.

The attending veterinarian, exposed to the diseased dolphin during treatment and necropsy, developed pustular dermatitis two weeks after the animal lied. Lymphangitis and lymphadenitis (subtrochlear and axillary) developed one week later. When antibiotic, treatment based on cultures was unsuccessful , a skin biopsy was performed.

Materials and Methods

All dolphin tissues were examined by light microscopy and immunofluorescence techniques.(23) Serial serum samples were analyzed for antibodies specific for Blastomyces dermatitidis by the microimmunodiffusion test.(24) The Veterinaria 8 skin biopsy was processed for fungal culture.

Results

Gross Observations

Gross lesions were noted in the dolphin lungs, stomach, liver, lymph nodes and the skin. The lungs were characterized by hemorrhage, edema, and severe necrosis and weighed 6.8 kg. There was no significant fluid either in the trachea or bronchi. Accentuation of lobular markings as well as hypertrophy were noted in the liver. Severe lymphadenitis was seen throughout the thorax. Small, firm nodules were observed in the stomach. The tissue surrounding the melon abscess showed necrosis and cellulitis extending 10 cm caudomedially and included the blubber and subcutaneous musculature.

Histopathologic Observations

Much of the lung parenchyma and bronchiole epithelium was totally effaced by myriads of spherical yeast cells.

The renal cortex contained discrete pyogranulomas with central yeast-like forms. Many renal corpuscles contained fungal cells organisms either filling Bowman's -pace or distending the glomerular tuft with little or no inflammation. The lesions were limited to the cortex, and the medulla was essentially normal.

Severe necrosis with minimal pyogranulomatous inflammation was present in the thoracic lymph nodes. It was in these nodes that the most dramatic numbers of yeast cells were present. The nodal architecture was virtually replaced by necrotic debris and myriads of yeast-like cells interrupted only by areas containing neutrophils and macrophages.

Other major organs, including spleen, gastrointestinal tract, liver, heart and skin showed large numbers of yeast cells.

The fungal cells seen in all affected tissues were morphologically compatible with the tissue form cells of B. dermatitidis.

Immunological Observations

Four of five sera taken from the dolphin from June 1984 to April 1985 contained the antibody diagnostic for blastomycosis. A trace precipitin response was noted in the January serum with a more intense precipitin response in samples taken thereafter.

All of the yeast-like forms in the tissues stained intensely with the fluorescein conjugated specific anti-B. dermatitidis globulin.

Culture Results

The fungal culture taken from the skin biopsy of the veterinarian's hand was identified as Blastomyces dermatitidis.

Discussion

Immunologic studies correlated with the histological identification of B. dermatitidis from the dolphin tissues, and the culture from the human revealed the same organism.

Blastomycosis is not considered autochthonous in Hawaii,(25) where only four cases have been reported.(a,b) Our dolphin had been in Hawaii almost a year after transport from an endemic area. The other cases had similar histories. Exposure in this case most likely had occurred in the Mississippi Sound, but the thought of spore inhalation in those coastal waters brings questions about the environmental source and viability of B. dermatitidis.

Although the infection was well established as indicated by the dissemination of organisms to all major organs, the rate of progression is unknown.

The fungal organisms were evidently transmitted to the veterianarian during his treatment of the dolphin, and he developed the primary cutaneous form of the disease.

B. dermatitidis should be considered as a differential diagnosis and zoonoses related to cetaceans in captivity. Factors, such as the mechanisms of the immune system, nutrition, stress and their interrelationships, are all poorly defined in cetaceans and may have been involved in the exacerbation of the disease process in this dolphin.

(a) Sawa T, Dept. of Agriculture, State of Hawaii, Honolulu, HI: Personal Communication, 1986.
(b)Higa H, Dept. of Health, State of Hawaii, Honolulu, HI: Personal Communication, 1986.

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