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Toxoplasma skin- and dye-test surveys of severely subnormal patients in Lincolnshire*
Published online by Cambridge University Press: 15 May 2009
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Of 918 severely subnormal patients in mental deficiency hospitals in Lincolnshire 917 were tested by the toxoplasmin skin tests, forty-nine out of 265 patients were dye tested because of a positive skin test or other indication. All patients in another group of 655 subnormals were dye tested, and comparison of these results with those of groups from the normal population showed that in children there was an excess of about 20% of dye-test positivity among the subnormals—a figure identical with that found by Thalhammer in Vienna.
The excess of positives became progressively less with increasing age and by middle age the incidence was the same in subnormals as among blood donors in the county. It is suggested that this indicates that patients in hospital are exposed to a lower risk of acquiring infection and that the higher incidence among adult males than among adult female defectives is due to the fact that more of them go out to work, many of them on farms. This factor could also explain the lower incidence of positivity in adult mongols and epileptics who are less commonly employable.
Possible explanations of the higher incidence among subnormal than among control children are discussed. Although it is tempting to assume that it indicates that some may be cases of congenital toxoplasmosis, the lack of gradient between child mongols, child epileptics and other subnormal children does not support this hypothesis. The numbers of mongol and epileptic children were too small to give statistically significant results. It is possible that the home environments of severely subnormal children exposed them to a higher risk of infection than did the homes of the control children and that the observed excess of dye and skin-test positivity may be due to increased incidence of acquired infection before their admission to hospital.
It was found that there was reasonable concordance between the dye test at a titre of 1/8 and skin sensitivity reactions exceeding 7 mm. in diameter, but poor agreement if 10 mm. was taken as the criterion of positivity.
Despite the lesser sensitivity of the skin test, the pattern of the results was the same as that observed in the dye-test survey, and the value of the skin-test for epidemiological surveys was confirmed.
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- Copyright © Cambridge University Press 1965
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