si/.ed (Schmidt, IIIU; Loiitze, lilST); Wright and Cram, 11)37; 

 Hall and Cram, 193!)). From a study of about 300 piinvorm- 

 infected families in Washington, D. C, it was apparent that 

 multiple eases are the rule rather than the exeeption and that 

 frequently all the children of the family, and one or both par- 

 ents, may be infected. Bozicevich and Brady (1938) found a 

 correlation between the size of the family and the incidence 

 of Enterobiiis, easily explained in that the larger the number of 

 persons in a family, the more chance there is for introduction 

 of the infection into the household and, once introduced, the 

 easier its spread, the infection increasing in a geometrical, not 

 an arithmetrical rate. Under institutional conditions Sawitz 

 et al found the incidence of infection much lower among chil- 

 dren occupying rooms with one or two beds than where larger 

 groups were quartered in dormitories. Families with pinworm 

 infections are found most numerous in older, comparatively 

 congested residential sections but are by no means confined to 

 those sections (Cram and Reardon, 1939); the social-economic 

 status is not limited to any one level. 



T.\BLE 12. — liwicJeticc of Enterobiiis vermicidaris according to 

 age and race of children in camps and iiiirxirii sclioolt:. 



Reported by 



Waxhington. D. C. 

 Race Age 



Xum- % Swabs 

 ber posi- per 

 .Sex exam, five person 



Bozicevich White' 6-18 M 230 31 1 



Bozicevich & Bradv White' 618 M 504 57 2 4 



Cram White (Jewish)' 6-12 MF 147 25 4 



Negro" 6-12 MF 63 21 4 



Ciam & Nolan White" 2- 5 MF 91 -55 av. 9 



Cram White"' 2- 5 MF 62 52 4 



Negro' 2- 5 M F 68 ^19 4 _ 



'Camps. "Private nursery school. 'Public nursery schools. 



CONTROI. 



Control of pinworm infection is extremely difficult. The 

 number of eggs deposited may be enormous, one worm being 

 capable of producing from 5,000 to 17,000 eggs (Reardon, 

 1938), and the time of development of eggs on the skin of the 

 perianal region is short, as little as 6 hours. The infected 

 individual may contaminate the hands while scratching or when 

 using the toilet and subsequently carry the eggs to the month 

 or may contaminate other objects. Eggs which fall off of the 

 person develop more slowly, depending on temperature and 

 humidity; they can pass through cloth and there is considerable 

 evidence that airborne infection is a possiliility (Lentze, 1932; 

 Oleinikov, 1929; Nolan and Reardon, 1939; Sondak, 1935). 

 In households and schools with infected members pinworm eggs 

 have been found in dust from a large variety of locations and 

 objects at various levels. The eggs may float on the surface 

 of water and a certain proportion would therefore remain on 

 the sides of wash bowls, bath tubs, laundry tubs and similar 

 containers when they are emptied. 



The eggs are very resistant to i)h3-sical and chemical agents. 

 Temperature and humidity influence the length of their sur 

 vival. Lentze (1935) found that a temperature of 55° C. and 

 above killed the eggs in a few seconds; at the optimum tempera- 

 ture (36° to 37° C.) on a damp base, as on the human skin, 

 especially under the nails, eggs survived for about 10 days. 

 Jones and Jacobs found that temperatures above 28° C, with 

 humidities below 50 percent, detinitely aft'ect the eggs within 

 24 hours; less than 10 percent of eggs survived after 2 to 3 

 hours and none survived after 16 hours at a temperature of 3))° 

 to 37° C. and relative humidity of 38 to 41 percent. On the 

 other hand, at lower temperatures, 20° to 24%° C, and higher 

 humidity, 62 to 91 percent, 30 percent of eggs survived 6 days; 

 on water at 3° to 5° C. a maximum of 93 percent survived 18 

 days. According to Sondak (1935), eggs were still viable after 

 drying at room temperatures averaging 10° to 12° C. for 3 

 weeks but not viable after 35 days. Exposure of eggs to mea- 

 sured quantities of monochromatic ultraviolet radiation (Hol- 

 laender, Jones and Jacobs, 1941 ; Jones, Hollaender and Jacobs, 

 1941) showed an increased sensitivity of the eggs at wave- 

 lengths below 2400A. As regards the effect of chemicals, Son 

 dak (1935) found that eggs were not killed by formalin in 

 strengths of 1, 2, 5, and 10 percent; by corrosive sublimate 

 1:1,000; by saturated solution of corrosive sublimate and cop- 

 per (eupric sulphate) ; by 5 percent antif ormin ; by 1 and 2 

 percent solutions of carbolic acid or by 1, 2, and 5 percent 

 lysol solutions, but they were killed by 5 percent carbolic acid 

 and by 10 percent lysol. 



Because of the large numbers of eggs scattered by an infected 

 individual and because of the resistance of the eggs, hygienic 

 measures alone can not be relied upon to control the spread of 



pinworm infection. This was pointed out by Wright and Cram 

 (1937) and was given a practical demonstration by D'Antoni 

 and Sawitz (1940) who put in force a vigorous cleanliness pro- 

 gram for (i weeks in one of the institutions studied by them; 

 at the end of that period swab examination showed an increase 

 from 38 percent to 51 percent in incidence of pinworms. The 

 greatust promise for control lies in medicinal treatment admin- 

 istered over a period which is sufficiently long to cover the 

 period of survival of eggs in the surroundings, tlms preventing 

 reinfection of the individual. 



Bibliography 



THE HOOKWORMS 



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324 



