To determine what role, if any, toxoplasmosis plays in the mental retardation of children, sera from 345 mentally retarded children were tested for the presence of antibodies to Toxoplasma gondii. The serological tests employed were the complement-fixation, the Sabin-Feldman dye test and the immunofluorescence test. The donors were also skin-tested with toxoplasmin.
Of 345 mentally retarded donors nine gave a positive skin reaction, 15 possessed complement-fixing antibodies, 21 had immunofluorescent antibodies and 45 had dye test antibodies to T. gondii.
The incidence of antibodies to T. gondii in the mentally retarded group was approximately the same as in the normal control group of the same age, and less than in the group suspected of having toxoplasmosis. It is concluded that in the children in this study toxoplasmosis played little or no role as a predisposing factor in the occurrence of congenital mental deficiency.