Utility of antigen testing for the diagnosis of ocular histoplasmosis in four cats: a case series and literature review.

Case series summaryThis case series describes the clinical utility of antigen testing for the diagnosis of feline ocular histoplasmosis. Four cats with suspected (n = 2) or confirmed (n = 2) ocular histoplasmosis are described: three from Oklahoma and one from California. In one case, serial urine antigen tests, as well as a serum antigen test for Histoplasma capsulatum, were negative; however, light microscopy identified microorganisms consistent with H capsulatum in ocular tissues at necropsy. In a further two cats with recurrent ocular histoplasmosis following long-term systemic antifungal therapy, Histoplasma species urine antigen concentrations were negative, but both cats improved clinically following systemic antifungal therapy and remained in apparent clinical remission after treatment cessation (9–16 months). The final cat displayed profound bilateral endophthalmitis; however, Histoplasma species antigen testing of vitreous humor and subretinal fluid from the left eye was negative. Intralesional ...