Experimental toxoplasmosis in calves and pregnant cows

Experimental Toxoplasma gondii infections were studied in pregnant cows and in calves. In tests to compare their virulence, three strains of the toxoplasmal parasite were red to cats; then fecal oocysts were collected and given per os to calves. In tests to determine their effects, virulent tachyzoites or oocysts were given to 10 calves and to 22 pregnant cows by the oral, IV, or intraamniotic routes. Clinical signs were fever and inappetence. One cow in early gestation aborted 24 days after IV administration of tachyzoites. Gross and microscopic changes were slight and nonspecific. Toxoplasmas were isolaated from brain or liver of 4 cows, placenta of 2 cows, gastric contents of 2 near-term fetuses, and blood and tissues of calves. Toxoplasmas were not isolated from control cows.