Cryptococcus neoformans var. grubii can be found in multiple environmental sources, although bird droppings (especially from pigeons) are the most common. While infections in humans usually occur among the immunocompromised, the fungus appears to act as a primary pathogen in dogs and cats. This may also be true for ferrets. Cryptococcosis has been repeatedly reported in Canada and Australia, but reports in the United States have been very limited. This case report documents the first antemortem diagnosis and successful treatment of cryptococcosis in a ferret in the United States. An 18-month-old, castrated male ferret presented with a 48-hour history of regurgitation. The ferret had an enlarged right submandibular lymph node, monocytosis, hypocalcemia, hypophosphatemia, hypoproteinemia, and hypoalbuminemia. All other findings were normal, and the ferret was active and in good body condition. Cytologic examination and culture of the enlarged lymph node confirmed infection with C neoformans var. grubii. The ferret was treated with itraconazole, 15 mg/kg orally Q 24 H. At recheck 3 weeks later, the owners reported no further regurgitation or development of any other clinical signs. Cryptococcus-antigen titer had dropped from > 1:4096 at presentation to 1:64. The lymph node had decreased to one third its initial size. Within 6 weeks, the lymph node had returned to normal size. Titers continued to steadily decline during subsequent rechecks and were negative nearly 10 months after initial presentation. A biochemical profile revealed resolution of all previous abnormalities. Treatment was continued for an additional 3 weeks after the negative titer.

COMMENTARY: The source of infection for this ferret was never found. However, this report drives home the point that C neoformans can infect ferrets as well as cats and dogs. Signs of cryptococcosis will vary according to the location and severity of disease, but possible infection should be included on a differential list in any ferrets that present with lymphadenopathy, swollen limbs, or respiratory signs. Neurologic signs have also been noted in cats and dogs. Treatment with an antifungal may require many months, although it is encouraging to note that in this case, hepatic enzymes remained within normal range after 10 months of itraconazole treatment. Cryptococcosis is not considered zoonotic, but owners of infected pets should be warned that there may be an increased environmental risk for them, especially if they are immunocompromised.

Diagnosis and successful treatment of Cryptococcus neoformans variety grubii in a domestic ferret. Hanley CS, MacWilliams P, Giles S, Pare J. CAN VET J 47:1015-1017, 2006.