Serodiagnosis of postnatally and prenatally induced toxoplasmosis in sheep.

Nineteen pregnant (45 to 90 days of gestation) and 9 nonpregnant ewes were inoculated orally with 1,000 or 10,000 oocysts of Toxoplasma gondii. Pregnant ewes were euthanatized at days 14 (2 ewes), 21 (1 ewe), 23 (1 ewe), 28 (2 ewes), 35 to 42 (6 ewes), and 49 to 62 (6 ewes), and antibody titers in fetal and maternal sera were assayed, using the modified agglutination, latex agglutination, indirect hemagglutination, and dye tests. Although all ewes developed antibody titers of greater than or equal to 1,024 within 28 days after inoculation, fetuses were seronegative up to 28 days, using the modified agglutination test. Toxoplasma gondii antibodies were found in fetuses, using the modified agglutination and dye tests 35 days after ewes were inoculated. Latex agglutination and indirect hemagglutination tests were insensitive for detection of T gondii antibodies in ovine fetal sera. Toxoplasma gondii antibody titers in nonpregnant ewes were similar to those in pregnant ewes. Passively acquired T gondii antibodies from the colostrum decreased from 1,024 to less than 16 between 49 and 56 days of age in 1 lamb and between 62 and 106 days in its twin.