Evidence that primary infection of Charollais sheep withToxoplasma gondiimay not prevent foetal infection and abortion in subsequent lambings

Abstract

SUMMARYA study carried out on a sheep farm examined whetherToxoplasma gondiifoetal infection and associated abortion occur in successive lambings. We identified 29 ewes that gave birth to lambs on at least 2 successive years over our study period, 2000–2003. Tissue samples from the progeny of these ewes were analysed by PCR to determine infection status withT. gondii.T. gondii-infected lambs were born in 31% of successive pregnancies.T. gondii-positive lambs were aborted in successive pregnancies in 21% of lambings during study period, 2000–2003. The frequency of successive abortions within this flock over the period 1992–2003 was 18%. If a lamb was congenitally infected there was a high risk (69%) that the successive lamb from that ewe would also be congenitally infected. Similarly, if a lamb was aborted there was a high risk (55%) of abortion in the next lamb produced. These data suggest that life-long immunity toT. gondiiinfections may not always be acquired following an initial infection and raises the question as to whether the mechanisms ofT. gondiitransmission prior to and during ovine pregnancies are fully understood.