The food handlers at a professional school in Philadelphia, Pa. were examined annually for intestinal protozoa for the seven years, 1932–39. Of the 190 persons examined, 50 were older, more permanent employees, who were examined on successive years an average of 3.2 times per person. The 140 student helpers were examined an average of 1.4 times per person. Methods were the same as for the survey of 1060 freshmen at the same institution.
Incidences were higher for the employee group, when single (first) examinations alone are compared, for Blastocystis, Total Protozoa, Endolimax, Endamoeba coli, Dientamoeba, Chilomastix and Enteromonas. The student group had an incidence of 10.7 per cent for E. histolytica as compared with 8 per cent for the employees after one examination. On one (first) examination the 140 students showed higher incidences for Total Protozoa, Endolimax, Endamoeba coli, E. histolytica, and Giardia, but lower for Dientamoeba as compared to the 1060 freshmen who were examined only once.
The incidences derived from 3.2 examinations of the employee group are considerably higher than for the first examination alone in respect to most of the items in the list. The added percentages for 1.4 examinations of the students in comparison with one examination alone are relatively slight. Of the 6 infections with E. histolytica detected in the employee group, four were found at the first examination, one at the fourth and one at the fifth. All of the 15 infections with this species discovered in the students were found at the first examination.
Persons found infected with E. histolytica were treated to eliminate the infection and in this connection daily examinations were made just before, during, and following, treatment. These additional examinations revealed very few additional infections.
The carriers of E. histolytica revealed no more gastro-intestinal symptoms than the others.
All six of the carriers of E. histolytica among the employees and one among the students lived in or near Philadelphia. The remainder came from homes in various parts of Pennsylvania and from other states.
The use of permanent fixed and stained slides added greatly to the number of positives for Endolimax, Endamoeba histolytica, Dientamoeba, Iodamoeba, and Enteromonas.