Seroprevalence of Toxoplasma gondii in harbor seals (Phoca vitulina) in southern Puget Sound, Washington

As part of the Puget Sound Ambient Monitoring Program of the Washington Dep artment of Fish and Wildlife, serum samples from 380 harbor seals (Phoca vi tulina) were tested for antibodies to Toxoplasma gondii in the modified agg lutination test (MAT) incorporating formalin-fixed tachyzoites and mercapto ethanol. Antibodies to T. gondii were found in 29 of 380 (7.6%) seals with titers of 1:25 in 13, 1:50 in 14, and greater than or equal to1:500 in 2 se als. Results indicate natural exposure of these wild marine mammals to T. g ondii oocysts.