Clinical and serologic evaluation of cats with cryptococcosis

To evaluate the long-term clinical outcomes and serologic changes in cryptococcal antigen and antibody titers in cats with confirmed Cryptococcus neoformans infection.

Prospective case series.

47 cats with cryptococcosis.

Cats included in this study were determined to have cryptococcosis on the basis of identification of C neoformans on histologic or cytologic examination, isolation of C neoformans in culture, or positive serologic test results for cryptococcal antigens. Information concerning the signalment, history, physical examination findings, FeLV and feline immunodeficiency virus status, serologic testing, treatment, and outcome for each cat was requested on a survey form. Follow-up measurements of serum cryptococcal antigen and antibody titers were requested for all surviving cats.

Signalment and clinical signs of cats with cryptococcosis reported here were consistent with previous reports. Treatment consisted primarily of azole antifungal drugs. All cats were seronegative for cryptococcal antibody titers, whether tested initially or at follow-up examination. All but 1 cat tested were seropositive for cryptococcal antigens when initially tested. Cats with and without clinical signs of C neoformans infection were seropositive for cryptococcal antigens months to years after initial diagnosis of cryptococcosis.

The results of this study indicate that serum titers to cryptococcal antigens in cats can persist with or without clinical signs for months to years after an initial diagnosis of cryptococcosis is made. Repeated evaluation of serum cryptococcal antigen titers is advised during the treatment of cats to monitor progress, evaluate prognosis, and guide cessation of treatment.