Methods to determine acute toxoplasmosis

On suspicion of primary infection, the specific IgM, IgA and IgG antibodies to the parasite can be determined. Again, several methods have been developed for this purpose, for example, ELISA, IFL, 'capture'-ELISA, ISAGA (Desmonts et al. 1981). IgM and IgG antibodies can be demonstrated from about 3-4 weeks after infection. With IFL, the specific IgM can be detectable up to 6 months after primary infection. ISAGA and semi-automatized assays seem to be more sensitive, demonstrating IgM up to a year after infection. In around 50 per cent of the cases, specific IgA can also be detected up to several months after infection. Specific IgG will persist for the rest of the infected person's life. The avidity of specific IgG antibodies can also be measured by an ELISA assay (Hedman et al. 1989). A recent primary infection can be indicated by a low avidity of the specific IgG antibodies.

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