Polymerase chain reaction for the detection of Toxoplasma gondii in aqueous humor of cats.

To develop Toxoplasma gondii B1 gene polymerase chain reaction (PCR) for use with aqueous humor of cats, and to report PCR and antibody detection results in naturally exposed cats with and without uveitis. Serum and aqueous humor samples from client-owned, healthy cats (n = 23) and client-owned cats with uveitis (n = 43). T gondii-specific IgM and IgG were measured in serum and aqueous humor from all cats. The Goldman-Witmer coefficient for ocular antibody production was calculated for cats positive for T gondii-specific IgM or IgG in aqueous humor. Aqueous humor from all cats was assessed by the B1 gene PCR. T gondii was detected in aqueous humor by PCR from 2 of 23 (8.7%) healthy cats and 8 of 43 (18.6%) cats with uveitis. T gondii-specific IgM in either serum or aqueous humor was detected in 5 of 8 (62.5%) cats with uveitis and T gondii in aqueous humor. All cats with uveitis and T gondii in aqueous humor had anterior segment disease. In 5 of 8 (62.5%) cats with uveitis and T gondii in aqueous humor, ocular production of T gondii antibodies was not detected. T gondii was not detected in aqueous humor from 14 of 17 (82.4%) cats with ocular production of T gondii-specific antibody. The presence of T gondii in aqueous humor may correlate to clinical disease in some, but not all, cats. T gondii-specific aqueous humor antibody tests and PCR should be used together to aid in the diagnosis of ocular toxoplasmosis in cats.