Isolation and genetic characterization of Toxoplasma gondii from mute swan (Cygnus olor) from the USA

a b s t r a c t Little is known of the genetic diversity of Toxoplasma gondii circulating in wildlife. In the present study, antibodies to T. gondii were determined in serum samples from 632 mute swans (Cygnus olor) collected from different areas of the USA. Sera were tested by T. gondii modified agglutination test; 54 (8.5%) of 632 samples were seropositive with titers of 25 in 28 sera, 50 in 22 sera, 100 in three samples, and 200 or higher in one swan. Hearts from 14 seropositive swans were bioassayed in mice and viable T. gondii (designated TgSwanUs1-3) were isolated from the hearts of three. These three T. gondii isolates were further propa- gated in cell culture, and DNA isolated from culture-derived tachyzoites was characterized using 11 PCR-RFLP markers (SAG1, 5 � - and 3