Relationship between Toxoplasma gondii seroprevalence and lamb marking in South Australian sheep flocks.

Abstract

Toxoplasmosis in sheep has negative impacts on reproductive performance. This study aimed to estimate the prevalence in Toxoplasma gondii infection in the South Australian sheep population, and assess any association between within-flock prevalence and reproductive efficiency (measured by lamb marking percentage), climatic region and rainfall. A total of 875 individual mixed-age breeding ewes from 29 South Australian properties were blood sampled with an average of 30.2 ewes per property (min 28, max 32). Sera were tested for T. gondii-specific IgG antibody using a commercial Modified Agglutination Test kit. Overall, 209 of 875 (23.9%; 95% confidence interval [CI] 16.3% to 31.4%) of individual ewes tested seropositive for T. gondii-specific IgG antibodies, with a flock level seroprevalence of 28/29 (96.6%, 95% CI 96.6% to 100%). On individual farms, the seroprevalence ranged from 0% to 93.3%. Analysis showed that Kangaroo Island properties had significantly higher mean seroprevalence than any mainland climatic regions, and that the mainland regions did not significantly differ from each other. Linear regression revealed a significant association between seroprevalence and lamb marking percentage, with a slope of -5.4% lamb marking per +10% seroprevalence.