Abstract
Blastomyces dermatitidis is a dimorphic fungus and the etiologic agent of North American
blastomycosis.1 Blastomycosis commonly occurs as a primary pulmonary infection with occasional spread to other
viscera.1,3 The disease has been described most often in dogs, cats, horses, and humans, but is apparently rare in
marine mammals.1-3 It has been reported once in a captive Stellar sea lion3 and once in a captive
dolphin.2 This report describes two cases of fatal blastomycosis in long-term captive California sea lions at the
Indianapolis Zoo. Sea lion 1 was an approximately 29-yr-old long-term captive male, kept at the Indianapolis Zoo for 8 yr prior to
death in 1996. The animal had a chronic history of clouded corneas attributed to aging. Two weeks prior to death it developed
lethargy and a tense abdomen and urinalysis revealed hematuria and pyuria. Aerobic culture of the urine revealed Escherichia
coli, Klebsiella pneumoniae and Edwardsiella sp. The sea lion did not respond to antibiotic therapy and died
following a brief period of tachypnea. Necropsy revealed spherical nodules in the skin, lungs, on the pleural surfaces, and in a
mesenteric lymph node. Mycotic culture of fluid from the chest revealed Blastomyces dermatitidis, and the identification was
confirmed by PCR probe of cultured fungus. The animal also had chronic renal disease. Sea lion 2 was a captive-born 13-yr-old
female that had been at the Indianapolis Zoo 1 yr prior to death in 1998. The animal had a chronic history of skin abrasion over
the flippers, pectoral and pelvic areas that was believed to be associated with rubbing in the tank. The sea lion also had a
long-term history of clouded corneas believed to be associated with osmoregulatory disturbances due to inappropriate water quality.
The animal developed a 2-wk history of lethargy, inappetence and tachypnea. During this time, serology was positive for
Blastomyces antibody, and the animal was treated for 3 days prior to death with Itraconazol (Sporanox7 Itraconazole capsules
100mg, Janssen Pharmaceutica Inc., Titusville, NJ 08560 USA; 200 mg p.o. q 24 hr x 2 days, then 400 mg b.i.d. x 1 day). After a
brief mild improvement in clinical signs, the animal died. Necropsy revealed multiple nodules in the lungs and pleura.
Blastomyces sp. was isolated from mycotic culture of a pleural lesion. Histopathology of both animals revealed granulomatous
inflammation associated with yeasts in lung and mesenteric lymph node from both animals. Sea lion 1 also had mycotica granulomas in
the spleen. Sea lion 2 had mycotic granulomas in tracheal-bronchial lymph node, mammary gland, skin, skeletal muscle, and kidney.
The granulomas were comprised predominantly of macrophages and multinucleate giant cells with fewer neutrophils. Extracellular and
intracellular yeasts were frequently detected in areas of inflammation. The yeast were round and 8-20µ, with broad based
budding, and a thick walled capsule. Immunohistochemistry was positive for Blastomyces sp. in sections of affected lung from
both animals.
Because lung was the most affected tissue, respiratory tract was presumed to be the primary route of infection,
but entry through skin abrasions may also have been possible. Aging, captive stressors and perhaps concurrent antibiotic therapy
(sea lion 1) may have compromised immune function in these animals, predisposing them to blastomycosis. In the United States,
Blastomyces dermatitidis is endemic in the environment of the Mississippi, Missouri and Ohio River drainages. Blastomycosis
should be considered a differential diagnosis for respiratory disease in captive sea lions from these areas.
Acknowledgments
We appreciate the technical expertise of Histology Consulting Service for histology slides, and the Indiana
Veterinary Diagnostic Laboratory for Blastomyces serology.
References
1. Hungerford LL, CL Campbell, AR Smith. 1998. Veterinary Mycology laboratory Manual. Iowa
State University Press, Ames, Iowa, Pp. 32-35.
2. Sweeney JC, G Migaki, PM Vainik, RH Conklin. 1976. Systemic mycoses of marine mammals. J. Am.
Vet. Med. Assoc. 169:946-948.
3. Williamson WM, LS Lombard, RE Getty. 1959. North American blastomycosis in a northern sea lion.
J. Am. Vet. Med. Assoc. 153:513-515.