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A description of the incidence of threadworms in United States of America has a familiar ring. It was found to be highest in school-children, lowest in adults, and intermediate in pre-school children*. There was evidence that if young children attended nursery schools, their incidence rose until it equalled that of children of school age. The highest incidence recorded was in a group of 504 boys aged 6-16 years, of whom 57 per cent, were infested. When families in which one member was known to be infested were investigated (cf. our studies of household contacts of poliomyelitis cases), an unusually high incidence was found. In 286 white families, 1,353 persons were examined ; 72 per cent, of the children and 36 per cent, of the adults were infested. In 34 negro families, 172 persons were examined ; 51 per cent, of the children, but only 7 per cent, of the adults, were infested. A leading authority concluded that " even stringent measures cannot be relied on to control the infection." All this is reminiscent of some of the more puzzling aspects of poliomyelitis. Growing emphasis has been laid in recent years on the role of fecal organisms in the spread of the disease. It seems possible, therefore, that something might be learned, by analogy, if we look further into the threadworm question. This leads us to a startling aspect of the epidemiology of threadworms, only recently recognized, but already well established as a fact on both sides of the Atlantic. It is now known that where threadworm infestation is common (and where is it not ?) the eggs can be recovered in large numbers from the dust in schools and in homes, where they seem to be blown about everywhere. The height above the floor of the surface examined is immaterial. In the homes of infested families they have been found in all rooms, and at all levels from the floor to the ceiling lights. In the United States of America, in 7 infested households, 91-7 per cent, of 241 samples of dust yielded eggs. The largest numbers were found in the bedrooms, and about half of the eggs were viable or had recently been so. In Amsterdam, where all children are said to be infested, the numbers of eggs found"j" on a square foot of surface was 119 in a school dining-hall, 305 in class-rooms, and 5,000 in closets. More eggs were found in girls' closets, but girls were not more heavily infested than boys. The main source of the eggs appeared to be the anal region, where they are deposited by the female worm during the hours of sleep Movements of the clothing cause them to be rubbed off, and they are then spread about in the dust. Bedmaking was noted as being favourable to dissemination. Dust-borne spread has been accepted as an important source of light infestation, thereafter convertible by finger transference into a severe and active condition. Does this throw any light on the poliomyelitis problem ? I think it may. We know that the virus of poliomyelitis is principally eliminated in the feces and that contacts and persons who have had abortive attacks may harbour it for weeks or months in the intestine. We know that it may retain its infectivity in dried feces for a long time. If, therefore, the relatively enormous ova of Enterobius have been found so readily in the dust in schools and in private houses and have been proved to be blown about indoors and to be liable to inhalation or swallowing, surely it is reasonable to suppose that spread of the poliomyelitis virus may well take place in the same way—possibly at the same time. The ova themselves might be contaminated with infective virus ; tiny particles of dried feces, derived in a similar manner from the anal region of a poliomyelitis carrier, almost certainly must be, at least occasionally.

* Eloise B. Gram (1944): Am. J. Dis. Child, 68, 376. t See " Threadworms," Lancet, 18th May, 1946, p. 742—various references.

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