Some Factors in the Epidemiology of Histoplasmin Sensitivity in Williamson County, Tennessee

Abstract

Studies of the prevalence of histoplasmin sensitivity in 5044 Williamson Co. residents revealed that all segments of the popula-tion come in contact with the sensitizing agent. The percentage of positive reactors is 25 under the age of one, then rises abruptly to a peak of 87 in those 10-14 yrs. of age, after which there is a steady decline in the occurrence of sensitivity. No differences in the percentage of positive reactors were noted in males and females at any age. Negroes generally showed a lower prevalence of sensitivity than whites, but the greatest differences were observed in those under 5 yrs. of age. After an avg. interval of 25 months, 15.8% of 506 originally positive individuals were negative when retested. This loss of sensitivity varied with age, and was highest during the first 5 yrs. of life, and again at 40 yrs. of age and over. In children under five yrs. of age the occurrence of allergy to histoplasmin was lowest during the winter and early spring. The percentage of positive reactors rose during the summer to a peak in the fall and then declined. In children under 15 yrs. of age, 86.1% who lived in a damp environment showed a positive reaction, while only 48.9% of those in a dry environment reacted. Possible explanations for the above observations are offered.