Cryptococcal infection in cats: factors influencing treatment outcome, and results of sequential serum antigen titers in 35 cats.

The relationship between treatment outcome and location of cryptococcal infection, gender, magnitude of pretreatment cryptococcal antigen titers, results of feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) serology, and serial changes in antigen titers during and after treatment were evaluated in a prospective and nonrandomized study of 35 cats with cryptococcosis. A commercial cryptococcal latex agglutination kit (CALAS; Meridian Diagnostic Inc, Cincinnati, OH) was used to detect cryptococcal antigen in sera. All cats were treated with itraconazole (Sporanox; Janssen Pharmaceutica Inc, Titusville, NJ). Pretreatment mean log titers for serum cryptococcal antigen were not influenced by location of the infection. Treatment outcome was not influenced by gender, location of the infection, or magnitude of pretreatment serum antigen titer. Treatment outcome was influenced by FeLV and FIV status; cats seropositive for FeLV or FIV had a higher likelihood of treatment failure (P = .008). The cryptococcal antigen titers of cats successfully treated decreased with significant linearity over time during treatment (r = -.64, P < .000001), whereas the corresponding titers for cats not treated successfully did not decrease with significant linearity (r = -.03, P > .9). For cats in which treatment was successful, antigen titers decreased significantly from pretreatment values by 1.3 orders of magnitude at 2 months after initiation of treatment. By 10 months after initiating treatment, log titers decreased by at least 2 orders of magnitude in all cats successfully treated, and 9 of 16 cats had undetectable titers. In contrast, in 5 of 6 cats in which treatment failed, antigen titers were unchanged or increased in magnitude even after at least 6 months of treatment.