TOXOPLASMOSIS IN RATS (RATTUS-NORVEGICUS) - CONGENITAL TRANSMISSION TO FIRST AND 2ND-GENERATION OFFSPRING AND ISOLATION OF TOXOPLASMA-GONDII FROM SERONEGATIVE RATS

To study congenital transmission of Toxoplasma gondii during acute and chronic infections, 4 pregnant Sprague-Dawley rats were each fed 1000 0 oocysts of the VEG strain. Toxoplasma gondii was recovered from 33, 55, 83 and 57 % of rats (F1) when darns were inoculated at 6, 9, 12 or 15 days of gestation, respectively. Progeny of 15 congenitally infect ed female rats were examined for T. gondii. Toxoplasma gondii was reco vered from tissues of 1 of 155 rats (F2) born to congenitally infected darns. A total of 4 (F2) females were mated; 0 of 40 (F3) rats born t o them were infected. None of the acutely infected 4 dams that had giv en birth to congenitally infected litters produced congenitally infect ed offspring during the second pregnancy. Thus, unlike mice, evidence for repeated congenital transmission of T. gondii in the rat was found in < 1 % of cases. Of the 16 congenitally T. gondii infected pups wit h demonstrable tissue cysts, 5 were seronegative (< 1:4) in the Sabin- Feldman dye test and 5 were seronegative (< 1:20) in the modified aggl utination test by the use of whole formalinized tachyzoites and mercap toethanol.