THE PREVALENCE OF INTESTINAL HELMINTHS IN RELIGIOUS GROUPS OF A RURAL COMMUNITY NEAR CALCUTTA 1

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1 Copyrifbt C IS by The John* opkins University VoL 8, No. J Print* in UJS.A. TE PREVALENCE OF INTESTINAL ELINTS IN RELIGIOUS GROUPS OF A RURAL COUNITY NEAR CALCUTTA A. B. COWDURY, G. A. SCAD' AUD E. L. SCILLER (Received for publication August, 6) Chowdhury, A. B. (Calcutta School of Tropical edicine, Calcutta, India), Schad, G. A. and Schiller, E. L (The Johns opkins Univ. School of ygiene, Baltimore, d. 5). The prevalence of intestinal helminths in religious groups of a rural community near Calcutta. Amer. J. Epkl., 68, 8: -.The results of a parasitological survey, designed to assure more equivalent representation of uslims and indus in sampling the population of Bandipur Union, confirmed a tentative conclusion, drawn from an earlier study, that the prevalence of ascariasis was significantly greater in uslims. In contrast, hookworm infections were more prevalent among indus. A comparison, according to age classes in the two religious groups, revealed that the prevalence of ancylostomiasis during early childhood was similar in both groups, but in late childhood the prevalence in indu children exceeded that in uslims. This difference was maintained in the older age classes, but the magnitude of the difference diminished. Chernin () reported that, in a group of industrial workers employed in a jute mill near Calcutta, Ascaris and Trichuris infections were more prevalent in uslims than in indus. In 6-6, Chowdhury and Schiller () examined about, villagers in a rural area 4 miles north of Calcutta. Ascaris and ir ThiB project was conducted under the sponsorship of the Johns opkins Center for edical Research and Training program in Calcutta in cooperation with the Calcutta School of Tropical edicine, with financial asitance from United States Public ealth Service Grant No. 5 ROTW4CIC. 'Professor and Chairman, Division of Parasitology, Calcutta School of Tropical edicine, Calcutta, India. * Assistant Professor, Department of Pathobiology, School of ygiene and Public ealth, The Johns opkins University, 66 North Wolfe Street, Baltimore, aryland 5: 'Professor, Department of Pathobiology, School of ygiene and Public ealth, The Johns opkins University, Baltimore, aryland 5. Trichuris were again more prevalent in uslims. owever, since they had planned a general survey of parasitism in a rural population, the proportion of uslims in the sample population was low, which represents the actual structure of the population of the area. We, on the other hand, were specifically concerned with the question of the prevalence of Ascaris in religious groups, and therefore a disproportionately large sample of the uslim population was deliberately included to obtain more nearly equal representation of the two religious groups. STJBVBY ETODS The investigation was conducted in the Bandipur Union, District of ooghly, West Bengal. This is the rural area surveyed by Chowdhury and Schiller (), who provide additional general information. According to the published statistics Downloaded from at Pennsylvania State University on ay, 6

2 4 COWDUBY, SCAD AND SCILLEB TABLE Prevalence of intestinal helminths in religious groups in the Bandipur Union No. of stools Ascaris Positive for helminths (%) ookworm Tritkuru Others ahalla uslim indu Lalpur Both villages uslim indu uslim indu (), uslims comprise about 5 per cent of the population of the Bandipur Union. Because they reside in many of the 6 villages constituting the Union, few villages contain a sizable uslim population. uslim families, in general, live in clusters of houses partly separated from those of the neighboring indu majority. The latter are, of course, more generally distributed throughout the study area. Two villages, ahalla and Lalpur, were chosen for investigation since their uslim populations are relatively large. ahalla is small enough, both in area and population, to allow inclusion of all uslims in the sample. These were compared to a indu population from households chosen at random. In the larger village, Lalpur, both groups were randomized on a household basis. From the households chosen, 54 individuals contributed stool specimens. Stool specimens were collected in paper cups which, were distributed to all members of a household in the evening, and on the following morning cups containing specimens were collected. These were kept cold in an ice-chest for transportation to Calcutta. Individuals who failed to provide specimens were reminded on the evenings preceding subsequent days of collection. Non-cooperators were removed from the list to be sampled after a maximum of three requests. All stools were examined by directsmear and by salt-flotation technique, the solution having a specific gravity of. RESULTS Table shows the prevalence of several intestinal helminths in the religious groups of Lalpur and ahalla. The prevalence of Ascaris was significantly higher in the uslims. uslims of our study group also were more frequently parasitized by Trichuris, but too few positive stools were obtained for statistical analysis. Contrary to our expectation, a statistically significant difference in the prevalence of hookworm was also observed. It appeared that hookworm infections were more prevalent among indus in these villages. Since the prevalence of Ascaris is low in all groups throughout the area, there were too few positive cases for statistical analysis of data for individual villages. owever, when the data from both villages were combined, the difference in prevalence, thirteen per cent for uslims and two per cent for indus, 4 6 Downloaded from at Pennsylvania State University on ay, 6

3 PREVALENCE OF INTESTINAL ELINTS IN BUAL INDIA 5 TABUS Distribution of hookworms in age classes of uslims and indus in ahalla and Lalpur, Bandipur Union, West Bengal (64) Age group (yean) tulimi () & iodtu () treated lepanteljr iO 4+ Totals Number examined Number positive for hookworms % positive for hookworms uslims & indus combined Number examined Number positive for hookworms % positive for hookworms is highly significant (p <.). Thus, Ascaris, and probably also Trichuris, both of which depend upon ingestion of embryonated eggs to gain entrance to man, were more prevalent in the uslims. In contrast, hookworm prevalence is high throughout the Bandipur Union. Therefore, statistical analysis of the data for individual villages is possible. In all comparisons, the prevalence of hookworms in indus exceeded that in uslims, and the differences were highly significant. (ahalla, p <.; Lalpur p <.; both villages p <.). It is instructive to compare the prevalence of hookworms in age classes of the two religious groups (table ). Although the number of individuals comprising age classes within religious groups is occasionally small, a general pattern of difference between the groups is revealed. Infection is acquired in early childhood, and initially the prevalence is similar in both religious groups. owever, the prevalence in indu children rapidly attains a level exceeding that in uslims. In the older age classes, the difference is maintained although the magnitude of the difference diminishes. Apparently, helminths possessing the ability to penetrate the skin have a much greater opportunity to infect residents of Bandipur than do those dependent upon ingestion, and for reasons not yet understood, indu residents appear to be more vulnerable to the former than are uslims. Additional evidence in support of the observation that these religious differences in prevalence of helminthiasis exist is provided by hematological data. Table shows that almost twice as many uslims as indus had eosinophil counts exceeding per cent. DISCUSSION The demonstrable differences in prevalence of Ascaris were expected, and 8 Downloaded from at Pennsylvania State University on ay, 6

4 6 COWDCBY, SCAD AND SCILLEB TABLE Number and percentage of populcuion sample of uslims and indus in various eosinophil groups Totalfl No iulinu % No indus % confirm a long-standing supposition based on the experience of the staff of the Calcutta School of Tropical edicine and on the literature cited in our introduction. owever, it is difficult to provide a satisfactory explanation of both the low prevalence in all groups and the difference in prevalence between indus and uslims. The generally low prevalence may be attributable, in part, to soil texture. Beaver (4) has shown that areas with sandy soil are unfavorable for the survival and transmission of Ascaris. owever, at best, this is a partial explanation of the generally low prevalence of Ascaris, because soils other than sandy soils occur in Bandipur. Any attempt to explain the difference in prevalence of Ascaris between religious groups is even more difficult. In rural West Bengal, there is little apparent difference between the religious groups in most aspecte of life. Such few differences as are well known Beem unrelated to the transmission of Ascaris. Chernin () suggested general differences in household cleanliness, but, if such is the case, it will be difficult to provide substantial evidence. The difference in the prevalence of hookworms was unexpected and cannot be explained by the age and sex distributions for the two religious groups. These distributions were too similar for the two groups to account for the difference in prevalence. It is conceivable that differences in occupation or in the wearing of shoes in the groups we compared could explain our observations. Further work is required to provide information on these factors. Differences in eosinophil counts between the religious groups had not been reported previously, and no satisfactory explanation of this difference can be given at present. SUARY In a rural population residing 4 miles north of Calcutta, it was confirmed that the prevalence of Ascaris in uslims exceeds that in indus. Contrary to expectation, a significant difference in prevalence of hookworm infection was noted in the population surveyed, indus having the higher prevalence. Explanations for the generally low prevalence of Ascaris, and for differences in prevalence of both Ascaris and hookworms in the population examined are at present rather speculative. The subtle behavioral differences suspected to be responsible for the different prevalences of Ascaris in religious groups require elucidation by a specialist in the behavioral sciences. To obtain scientifically acceptable data, a cooperative effort involving a behaviorist and a parasitologist is considered desirable. REFERENCES. Chernin, E. Problems in tropical public health among workers at a jute mill near Calcutta. II. A study of intestinal para- Downloaded from at Pennsylvania State University on ay, 6

5 PREVALENCE OF INTESTINAL ELINTS IN BUBAL INDIA sites in the labor force. Amer. J. Trop. ed. yg., 64, S: Chowdhury, A. B. and E. Schiller. A survey of parasitic infections in a rural community near Calcutta. Amer. J. Epid., 88,5:-.. Report on model health and ideal registration units, West Bengal, January to December, 6. Vital Statistics Special Reports, July 84. Directorate of ealth Services (Vital Statistics Division), Government of West Bengal. 4. Beaver, P. C. Observations of the epidemiology of ascariasis in a region of high hookworm prevalence. J. Parasitol., 5, 8: 445. Downloaded from at Pennsylvania State University on ay, 6