Detection of T. gondii Antibodies in Dog Heart Juice and Sera

Sera (n = 260) and heart juice (n = 81) from 341 dogs were tested for T. gondii antibodies using a modified agglutination test (MAT) (Dubey and Desmonts, 1987). Whole formalin-treated T. gondii tachyzoites were obtained from the University of Tennessee Research Foundation (Dr. CL Su, Knoxville, TN, USA). All heart juice and serum samples collected from 2015 to 2018 were tested at a titer of 1:25; the dilution was subsequently doubled to a titer of 1:1,600 ( Table 1 ). Serum samples collected from 2020 to 2021 were tested at a titer of 1:5 and 1:10. Positive samples were tested at a titer of 1:25; the dilution was subsequently doubled to a titer of 1:200 ( Table 1 ). Negative and positive controls were included in each plate. Heart juice and serum samples with a titer of ≥1:25 were considered as a sign of exposure to this parasite.