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Anti-''Toxoplasma gondii'' IgG antibodies can be detected in the maternal circulation from thirty days post-infection and remain increased for years afterwards. This means that for clinical diagnosis, IgG titres must be measured in paired serum samples taken 3-4 weeks apart, and must show at least a four-fold increase in titre<sup>3</sup>. In an outbreak of disease, this time scale may be too great to be useful. IgM antibodies become apparent sooner after infection and persist for a much shorter time, and so increased IgM titres are consistent with recent infection.
Anti-''Toxoplasma gondii'' IgG antibodies can be detected in the maternal circulation from thirty days post-infection and remain increased for years afterwards. This means that for clinical diagnosis, IgG titres must be measured in paired serum samples taken 3-4 weeks apart, and must show at least a four-fold increase in titre<sup>3</sup>. In an outbreak of disease, this time scale may be too great to be useful. IgM antibodies become apparent sooner after infection and persist for a much shorter time, and so increased IgM titres are consistent with recent infection.
Serology is the usual method of diagnosis in the VI labs and gives fairly quick results. Indirect fluorescent antibody test to detect toxoplasma antibody in foetal fluids is the most accurate method, but if abortion products are not available latex agglutination test can be performed on blood from the ewe. Interpretation of titres from the latex test can be subjective - low titres, e.g. 1/80, show exposure at some point whereas higher titres >160 suggest recent exposure and abortion likely due to toxoplasmosis.
===Pathology===
===Pathology===