HUMAN INFESTATION WITH THE DWARF TAPEWORM (HYMENOLEPIS NANA) IN THE SOUTHERN UNITED STATES.1 BY Downloaded from https://academic.oup.com/aje/article/23/1/25/182937 by guest on 27 September 2021 G. F. OTTO. (Received for publication September 6, 1935.) Human infestation with the dwarf tapeworm has been reported from a wide variety of places in the United States but most of the evidence suggests that it is largely restricted to the southern part of the country. Even in the southern United States the incidence is low according to most of the data. Of the older surveys Greil (1915) re- ports 6 per cent dwarf tapeworm in 665 children examined in Alabama. The Rockefeller Sanitary Commission for the Eradication of Hook- worm Disease Reports for 1914 and 1915 record from 0 to 2.5 per cent dwarf tapeworm in eleven southern states (Alabama, Arkansas, Geor- gia, Kentucky, Louisiana, Mississippi, North and South Carolina, Ten- nessee, Texas, and Virginia) with an average of 1.8 per cent in the 141,247 persons examined. Wood (1912) tabulated the results of 62,786 routine fecal examinations made in the state laboratories of eight southern states (Arkansas, Florida, Georgia, Kentucky, Missis- sippi, North Carolina, Tennessee, and Virginia) and found an average of less than 1 per cent infection with this worm. Of the more recent reports on the frequency of the dwarf tapeworm in the general population, three are based on extensive surveys. Spindler (1929) records that 3.6 per cent of the 2,152 persons of all ages examined in southwest Virginia were positive; Keller, Leathers, and Bishop (1932) report 3.5, 2.9, and 1.5 per cent in eastern, central and western Tennessee; and Keller and Leathers (1934) report 0.4 per cent in Mississippi. Spindler notes that only three cases were found in persons over 14 years and Keller, Leathers and Bishop and Keller and Leathers record a drop in the incidence in the age groups above 14 years although the drop is less marked in the Mississippi data. In both Tennessee and Mississippi, Keller and his co-workers report a lower incidence in negroes than in whites. 1 From the Department of Helminthology of the School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, Md. 25 26 G. F. OTTO The data here presented were collected incidental to our ascaris studies in the southern United States (Otto and Cort, 1934) and part of them have already been utilized in reports from Virginia and Ten- nessee cited above. In these studies stools were collected and stored at 0-10° C. until examined by the Stoll dilution egg counting method Downloaded from https://academic.oup.com/aje/article/23/1/25/182937 by guest on 27 September 2021 (Stoll, 1923; Stoll and Hausheer, 1926). It is possible, but not likely, that the storage destroyed the eggs althought it undoubtedly killed them. On the other hand the decinormal NaOH used in the Stoll method is destructive to the eggs of H. nana and partially destroyed eggs have been seen in the course of routine examinations so that no attempt was made to determine the intensity of infestation by egg counting. It seems unlikely that the destruction of all of the eggs in a specimen occurred very often. Therefore, since this method will pick up lighter infestations (if there is no destruction of eggs, as in the case of ascaris, trichuris and hookworm) than will the simple smear (Hausheer and Herrick, 1926; Keller, 1934), it seems probable that the incidence of Hymenolepis nana here recorded is comparable to what would have been obtained by the smear method. Since the infestations seem to be quite uniformly distributed through the rural districts of the mountains of southeastern United States, the data from eastern and central Tennessee and Kentucky are combined to give a picture of the age and sex distribution of the infec- tion. Only data from whites are included in this tabulation, the few negroes examined, being discarded. It will be seen from table 1 that TABLE 1. Distribution of Hymenolepis nana according to age and sex among the rvral whites of eastern and central Tennessee and Kentucky. Males Females Males and females Age group Num- Num- Per Num- Num- Per Num- Num- Per ber ber cent ber ber cent ber ber cent exam- posi- posi- exam- posi- posi- exam- posi- posi- ined tive tive ined tive tive ined tive tive 0-4 1,210 13 1.1 1,173 27 2.3 2,383 40 1.7 5-9 4,175 145 3.5 4,327 194 4.5 8,502 339 4.0 10-14 3,837 134 3.5 3,874 152 3.9 7,711 286 3.7 15-19 899 16 1.8 839 15 1.8 1,738 31 1.8 20 + 622 6 1.0 696 6 0.9 1,318 12 0.9 5-14 8,012 279 3.5 8,201 346 4.2 16,213 625 3.9 Total 10,743 314 2.9 10,909 394 3.6 21,652 708 3.3 the incidence is somewhat higher (twice in 0-4 year group) in females than males up to 14 years. No satisfactory explanation can be offered INFESTATION WITH DWARF TAPEWORM 27 for this difference. However, in both sexes it is evident that the greatest infestation occurs in the children of school age (5-14 years). The school age group (5-14 years), therefore, is a very satisfactory group to use in making a comparison of the infestations in the several areas studied. In this series the school age group is further desirable for this purpose since the representation is inadequate among the Downloaded from https://academic.oup.com/aje/article/23/1/25/182937 by guest on 27 September 2021 adults and pre-school age children in certain of the areas studied. Thus a comparison on the basis of total examinations made would result in an uneven weighing of the incidence. Accordingly a comparison is given in table 2 of findings in school TABLE 2. The incidence of Hymenolepis nana in children (negro and white, male and female, 5-14 years) in various areas in the southern United States. Except where otherwise indicated these data are from rural areas. Number Number Percentage Area examined positive positive Eastern and central Tennessee and Kentucky (Mts.). 16,213 625 3.9 Eastern Kentucky—mining camps (Mts.) 611 59 9.3 Western Tennessee 3,315 64 1.9 Columbus County, North Carolina 546 0 0 Central and northern Florida 748 1 0.1 South central Louisiana ... .. ... 1,406 21 1.5 Southern Arkansas .' 797 6 0.8 Northern Arkansas 1,886 22 1.2 Mississippi (Keller, Leathers and Bishop, 1932)*.... 23,174 125 0.5 * Whites only. children (white and negroes, 5-14 years): in (a) the rural mountainous areas of Tennessee and Kentucky (7 counties in eastern Kentucky, 37 counties in eastern and central Tennessee), (b) mining camps in the mountain areas (3 counties in eastern Kentucky), (c) the coastal plains of North Carolina (Columbus County), (d) rural Florida (9 counties in south central part of the state), (e) south central Louisiana (8 parishes), (/) lowlands of southern Arkansas (3 counties), (g) the Ozark moun- tains in Arkansas (16 counties), and (h) Mississippi (Keller and Leathers, 1934). The first point of interest in table 2 is the markedly higher inci- dence in the mining camps of Kentucky than in the rural communities of these same mountains. The other point of interest is the noticeable lower incidence in non-mountainous areas, most striking of which is the failure to find any infection in North Carolina and its almost com- plete absence in the part of Florida considered. 28 G. F. OTTO In table 3 the comparative incidence in negroes and whites (males and females 5-14 years) is given in these areas where the data warrant such a comparison. The negroes have a somewhat lower incidence than the whites just as Keller and his co-workers suggest in Tennessee and Mississippi, the only exception to this being in Columbus County, North Carolina, where both the negroes and whites examined were Downloaded from https://academic.oup.com/aje/article/23/1/25/182937 by guest on 27 September 2021 entirely free from the dwarf tapeworm infection. TABLE 3. The comparative incidence of Hymenolepis nana in white and negro children (males and females, 5-14 years) in the same rural areas. Whites Negroes Area Number Number Per cent Number Number Per cent examined positive positive examined positive positive Columbus County, N. C 222 0 0 324 0 0 Central and northern Florida. .. 510 I 0.2 238 0 0 South central Louisiana 785 13 1.7 621 8 1.3 Southern Arkansas 453 5 1.1 344 1 0.3 Total 1,970 19 1.0 1,527 9 0.6 COMMENT. It seems altogether probable from the data given and the literature cited that there has been no general reduction in the dwarf tapeworm incidence in the last two decades. Since there apparently has been no change in the habits or conditions which permit human infection in the United States, it might be well to inquire into the possible sources and methods of infection. The eggs of H. nana do not require any period of development outside of the body but are infective upon ingestion immediately upon being laid. Furthermore they are apparently quickly killed under natural conditions. Spindler (1929) showed that when the eggs were planted in feces on soil under natural and experimental conditions none could be recovered after 4 days.