Parasitology

Research Article

Evidence that primary infection of Charollais sheep with Toxoplasma gondii may not prevent foetal infection and abortion in subsequent lambings

E. K. MORLEYa1, R. H. WILLIAMSa1, J. M. HUGHESa1, D. THOMASSONa1, R. S. TERRYa2, P. DUNCANSONa1, J. E. SMITHa2 and G. HIDEa1 c1

a1 Centre for Parasitology and Disease, Biomedical Sciences Research Institute, School of Environment and Life Sciences, University of Salford, Salford M5 4WT, UK

a2 School of Biology, University of Leeds, Leeds LS2 9JT, UK

SUMMARY

A study carried out on a sheep farm examined whether Toxoplasma gondii foetal 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 with T. 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 to T. gondii infections may not always be acquired following an initial infection and raises the question as to whether the mechanisms of T. gondii transmission prior to and during ovine pregnancies are fully understood.

(Received June 22 2007)

(Revised August 20 2007)

(Accepted August 21 2007)

(Online publication October 09 2007)

Correspondence:

c1 Corresponding author: Centre for Parasitology and Disease, Biomedical Sciences Research Institute, School of Environment and Life Sciences, University of Salford, Salford M5 4WT, UK. Tel: +0161 295 3371. Fax: +0161 295 5015. E-mail: g.hide@salford.ac.uk

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