Experimental toxoplasmosis in pregnant cats.

Cysts of the K strain of Toxoplasma gondii were administered orally to nine pregnant cats having no antibody to the organism at each of the three stages of gestation, namely early (14 days), middle (30 days), and late (40 and 51 days). Premature and weak or deformed fetuses were observed in the offsprings delivered by mother cats infected with Toxoplasma in the early or middle stage of gestation, while the cats infected at the late stage were delivered of apparently healthy fetuses. Mother cats developed parasitemia excreting Toxoplasma oocysts in their feces and formed the antibody to the organism after the oral administration. Toxoplasma was recovered from the organs or tissues of all fetuses delivered by the mother cats infected in the early stage of gestation. All kittens born healthy from the cats infected in the middle stage of gestation were free from Toxoplasma, but 80% of the premature kittens were found to be infected. Toxoplasma was isolated also from the organs of about half the offsprings born healthy from the mother cats infected in the late stage of gestation. These results indicate that congenital infection with Toxoplasma may occur commonly and cause damage to the fetuses when pregnant cats are infected orally with Toxoplasma cysts in the early or middle stage of gestation.