title: High levels of congenital transmission of Toxoplasma gondii in longitudinal and cross-sectional studies on sheep farms provides evidence of vertical transmission in ovine hosts.
abstract: Recent research suggests that vertical transmission may play an important role in sustaining Toxoplasma gondii infection in some species. We report here that congenital transmission occurs at consistently high levels in pedigree Charollais and outbred sheep flocks sampled over a 3-year period. Overall rates of transmission per pregnancy determined by PCR based diagnosis, were consistent over time in a commercial sheep flock (69%) and in sympatric (60%) and allopatric (41%) populations of Charollais sheep. The result of this was that 53.7 % of lambs were acquiring an infection prior to birth: 46.4% of live lambs and 90.0% of dead lambs (in agreement with the association made between T. gondii and abortion). No significant differences were observed between lamb sexes. Although we cannot distinguish between congenital transmission occurring due to primary infection at pregnancy or reactivation of chronic infection during pregnancy, our observations of consistently high levels of congenital transmission over successive lambings favour the latter.
authors.affiliation: Centre for Parasitology, Molecular Epidemiology and Ecology, Bioscience Research Institute, School of Environment and Life Sciences, University of Salford, Salford M5 4WT, UK.
authors.forename: R H
authors.initials: RH
authors.lastname: Williams
authors.forename: E K
authors.initials: EK
authors.lastname: Morley
authors.forename: J M
authors.initials: JM
authors.lastname: Hughes
authors.forename: P
authors.initials: P
authors.lastname: Duncanson
authors.forename: R S
authors.initials: RS
authors.lastname: Terry
authors.forename: J E
authors.initials: JE
authors.lastname: Smith
authors.forename: G
authors.initials: G
authors.lastname: Hide
mesh_terms: D000034:Abortion, Veterinary / Q000469:parasitology*; D000818:Animals; D003430:Cross-Sectional Studies; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary*; D008137:Longitudinal Studies; D012756:Sheep; D012757:Sheep Diseases / Q000151:congenital* / Q000453:epidemiology* / Q000635:transmission; D014124:Toxoplasmosis, Animal / Q000151:congenital* / Q000453:epidemiology*