Clinical and serological response of pregnant gimmers to experimentally induced toxoplasmosis.

Thirty-five Scottish blackface gimmers in mid or late pregnancy were infected with Toxoplasma gondii by subcutaneous injection of 2000 tissue cysts. Approximately half the gimmers developed a mild febrile response between eight and 10 days after infection but were otherwise unaffected until lambing. Only seven gimmers lambed without loss; in the remainder abortions and neonatal deaths accounted for 27 of the 31 lambs born. These losses occurred predominantly among gimmers which had been infected in mid pregnancy. Antibody titres in the toxoplasma indirect haemagglutination test rose sharply after the 10th day post infection and remained high for over 200 days. The majority of abortions and neonatal deaths occurred after the 40th day post infection by which time mean indirect haemagglutination titres had exceeded 1/320.