Serological Response of a Rural Negro Population to the Sabin-Feldman Cytoplasm-Modifying Test for Toxoplasmosis

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  • National Institutes of Health, National Institute of Allergy and Infectious Diseases, Laboratory of Tropical Diseases


Using the Sabin-Feldman “dye test”, 987 sera from the rural, Negro population of Fayette County, Tennessee, were tested for antitoxoplasmic antibodies. The following conclusions were established:

  1. 1.There is no significant difference between the sexes at any age with regard to anti-toxoplasmic antibodies.
  2. 2.With the exception of the youngest age group, the percentage of positive titers in the population increases with age.
  3. 3.There is a highly significant shift of modal titer, from positive at a dilution of 1:64 or higher in persons under 20 years of age to 1:16 or less in persons 20 years of age or more.
  4. 4.Considerable evidence can be seen of a bimodal distribution of titers, with an abnormally large number of undiluted positive sera.
  5. 5.When the data for each age group are standardized to the actual census population, the overall prevalence of positive reactors is 29.9 per cent for all positive titers, and 21.8 per cent for titers of 1:16 or higher.

Author Notes

Located at the Medical School of the University of Tennessee, 874 Union Avenue, Memphis 3, Tennessee.