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Year : 2020  |  Volume : 64  |  Issue : 4  |  Page : 333-338  

Prevalence and risk factors of soil-transmitted helminth infections in school age children (6–14 years) – A cross-sectional study in an urban resettlement colony of Delhi

1 Ex-Post Graduate, Department of Community Medicine, Lady Hardinge Medical College, New Delhi, India
2 Professor, Department of Community Medicine, Lady Hardinge Medical College, New Delhi, India
3 Director Professor and Head, Department of Community Medicine, Lady Hardinge Medical College, New Delhi, India
4 Additional Director and Head, Division of Epidemiology, National Centre for Disease Control, Directorate General of Health Services (Government of India), Delhi, India

Date of Submission18-Feb-2020
Date of Decision12-May-2020
Date of Acceptance08-Oct-2020
Date of Web Publication11-Dec-2020

Correspondence Address:
Anita Shankar Acharya
Department of Community Medicine, Lady Hardinge Medical College, Shaheed Bhaghat Singh Marg, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijph.IJPH_120_20

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Background: Soil-transmitted helminth (STH) infections have adverse physical and mental effect, especially in preschool (3–6 years) and school-age children (6–14 years). They are associated with socio-behavioral factors of poverty and poor personal and community hygiene. Objectives: To determine the prevalence, intensity, and the type of helminths infection harbored by the school age children (6–14 years) and to examine the relationship between STH infection and their potential risk factors and associated variables. Methods: This cross-sectional study was conducted from January to December 2016 among 250 school age children residing in an urban resettlement colony of East Delhi. Data were collected using a semistructured interview schedule. Stool sample was tested using the Kato Katz technique. Data were analyzed in SPSS software version 16, and multivariable regression analysis was done to calculate the odds of various risk factors. Results: The prevalence of STH was found to be 54.8%, and majority (85.3%) of Ascaris and all Trichuris infections were of light intensity. Multivariable logistic regression analysis confirmed that children having poor handwashing behavior in school, irregular handwashing before eating, having pica, and lack of de-worming had higher odds of having STH infection. Conclusion: The prevalence of STH in the study area is substantially high, and the findings suggest that besides mass de-worming strategy, behavior change, and improvement in hygiene are required to control STH.

Keywords: Delhi, Kato Katz, school age children, soil-transmitted helminth

How to cite this article:
Gupta A, Acharya AS, Rasania SK, Ray TK, Jain SK. Prevalence and risk factors of soil-transmitted helminth infections in school age children (6–14 years) – A cross-sectional study in an urban resettlement colony of Delhi. Indian J Public Health 2020;64:333-8

How to cite this URL:
Gupta A, Acharya AS, Rasania SK, Ray TK, Jain SK. Prevalence and risk factors of soil-transmitted helminth infections in school age children (6–14 years) – A cross-sectional study in an urban resettlement colony of Delhi. Indian J Public Health [serial online] 2020 [cited 2022 Aug 19];64:333-8. Available from:

   Introduction Top

Soil-transmitted helminths (STHs) of major concern to humans from the public health point of view are roundworms (Ascaris lumbricoides), whipworm (Trichuris trichiura), and hookworms (Ancylostoma duodenaleand Necator americanus). All of them constitute most common gastrointestinal worm infestation in humans in tropical and subtropical countries.[1]

According to the World Health Organization (WHO), more than 1.5 billion people or 24% of the world population are infected with STHs worldwide. Among them, over 600 million school age children and 270 million preschool age children need regular treatment and preventive interventions for helminth infection.[2]

In India, 241 million children of the age group 1–14 years are at risk of STH infection. This represents approximately 68% of children in this age group (and 28% of all children at risk of STH infection globally).[3] Overall, South-Asia accounts for about one quarter of world's cases of STH infection with India sharing the highest, followed by Bangladesh.[2]

The tropical climatic conditions of India together with socio-behavioral factors of poverty and poor personal and community hygiene prevalent in the various parts of the country promote the spread of the STH infection.[4] Previous studies and surveys by National Center for Disease Control, New Delhi, have indicated that the overall STH prevalence varied widely from 0% to 83.2% in general.[5] The Global Atlas for Helminthic Infection[6] project collated results from 127 STH surveys implemented in India between 1999 and 2007 and computed a national estimate to about 21% prevalence of STH. Few studies have been carried out on STH prevalence in and around Delhi.[7],[8],[9],[10]

In spite of having huge educational, economic, and public importance, STHs are largely ignored by medical and international community due to three main reasons. First, they are more prevalent among impoverished people of the world. Second, since they lead to chronic health problems their clinical presentation is insidious, and finally, it is very difficult to quantify their effect on economic and educational development.[1]

It is necessary to estimate the baseline prevalence and intensity of infection in a community before initiation of any community wide parasite control. However, the prevalence and intensity data for STH infection are not available in most of the regions of India, and currently, Government of India is undertaking mapping of STH prevalence for all over the country, but such surveys and studies are being carried out in schools rather than in community. Hence, this study was conducted at the community level in an urban resettlement colony, Kalyanpuri in East Delhi for determining the prevalence, intensity, and the type of helminths infection harbored by the school age children (6–14 years) and to examine the relationship between STH infection and their potential risk factors and associated variables.

   Materials and Methods Top

Study design, area, and duration

This cross-sectional study was conducted in Kalyanpuri, an urban resettlement colony located in East Delhi, India. It has a tropical steppe type of climate with the extremes of temperature. Estimated population of the colony is 25,747 residing in 4612 households. There are 11 blocks in the area, each having approximately 1500–3500 population. The area has poor environmental cleanliness with all surveyed households having pour/flush latrine system well connected to the sewerage system. The water supply is through piped water supply and also by water tankers provided by Delhi Jal Board and is intermittent in frequency.

Data were collected from January to December 2016. All school age children (6–14 years) residing in the urban resettlement colony of Kalyanpuri constituted the study population.

Sample size and sampling technique

Sample size was calculated using the prevalence of 30% from previous study conducted by Ranjan et al.,[10] with a relative error of 20% within 95% confidence interval (CI) which came out to be 224. Keeping in mind of certain nonresponse, 250 study subjects were included in this study. Out of the total 11 blocks at Kalyanpuri, two blocks (Block No. 11 and 21) were selected randomly by the lottery method. Household was considered as sampling unit and child (6–14 years) as a study unit. From each block, households were selected using the simple random sampling by using a random number table. One eligible subject was studied from each household. In case of more than one appropriate age child in sampling unit, one child was selected randomly. In case, there was no eligible subject in the household, next household was approached. Overall, 125 study subjects were selected from each block as described above.

Tools and techniques – Data Collection

Two visits were made to each household for data collection. On the first visit, the eligible study subjects were interviewed face to face using a questionnaire for back ground and associated variables.

All the potential risk factors, associated variables of STH infection explored belonged to four variable categories – sociodemographic, environmental, behavioral, and hygiene-related factors as described and defined below.

Sociodemographic: age, gender, type of family, religion, socioeconomic status (Modified Kuppuswamy Scale CPI 2016),[11] mother's education, father's education, and school-going status. Environmental factors: Overcrowding, cooking slab, garbage disposal practices, distance to playground, distance to community bin behavioral factors: Handwashing in school and at home, handwashing before eating and after defecation, nail biting habit, Pica, de-worming, barefoot walking, and nail status. Handwashing behavior has been taken to be irregular if the study subjects missed washing hands even once before eating or after defecation. Hygiene: Personal hygiene, including score for nail, hair, skin, and clothing hygiene (0 = best and 3 = worst). Total hygiene score of zero was considered good hygiene; 1–4 = mildly poor; 5–8 = poor; and 9–12 = very poor.[12]

At the end of the visit, the subject was explained the method for stool collection. He/she was provided with clean wide mouth plastic bottle having a plastic spatula on the screw cap for stool sample collection. The sample was collected next morning on the second visit but in case of nonavailability or insufficient sample, it was collected another day.

Assessment of stool

The stool was examined within 4 h of collection with Kato Katz technique at the Urban Health Centre Kalyanpuri. The number of STH eggs was counted within each slide and eggs per gram of stool was calculated by the multiplication factor of Kato Katz kit. Intensity of infection was categorized as having light, moderate, or heavy STH's infections on the basis of threshold concentrations of their fecal worm eggs load.[1] For A. lumbricoides infection, the presence of 1–4999 epg (eggs per gram) was considered as light infection, between 5,000 and 49,999 epg as moderate and more than 50,000 epg as heavy infection. In case of Hookworm (A. duodenale and N. americanus), 1–1,999 epg was regarded as light, between 2,000 and 3999 as moderate and more than 4,000 as heavy infection while for T. trichiura, 1–999 epg was categorized as light, between 1,000 and 9,999 epg as moderate and more than 10,000 epg as heavy infection.

Ethical considerations

The study was approved by the Institutional Ethics Committee (Reference number LHMC/ECHR/2015/70 dated 30/10/2015). Patient consent form and participation information sheet were filled. Prior to data collection, informed written consent was obtained from mother or guardian and verbal assent from the child after explaining the purpose of the study. All information collected was kept confidential. All study subjects who had STH were given 400 mg albendazole tablet to chew and hygiene education was given to all study subjects including their mothers.

Statistical analysis

Data were entered and analyzed in SPSS Statistics for Windows, version 16.0 (SPSS Inc., Chicago, Ill., USA) after data cleaning. Continuous data were expressed in terms of mean and standard deviation, and 95% CI was used. Associations between parasitic infection and the variables within each factor were studied using the bivariate and multivariable logistic regression analysis. Multiple logistic regression was done with enter method model.

   Results Top

Sociodemographic characteristics

Out of total 250 school-aged children, 146 (58.4%) were boys and 104 (41.6%) girls. Overall, the mean age of participants was 9 ± 2.1 years. More than half (59.6%) of the subjects belonged to 6–9 years of age group. Majority of study subjects belonged to nuclear family (72.4%), were Hindus (74.4%) and attended government school (77.6%). More than half of study subjects (54.0%) belonged to upper lower socioeconomic status [Table 1].
Table 1: Bivariate and multivariable logistic regression analysis of factors associated with soil transmitted helminth infections

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Prevalence and intensity of STH infections

The overall prevalence of STH infections in our study was found 54.8% with A. lumbricoides (54.4%) being the most predominant, followed by T. trichiura (4.8%) while no hookworm was seen. Single infection (50.4%) was the most common followed by 4.4% dual infection [Table 2]. All Trichuris (100%) and most of the Ascaris (85.3%) infections were of light intensity, whereas 14% (n = 19) of Ascaris infections were of moderate intensity. Only one child was suffering from heavy intensity infection with Ascaris [Table 2].
Table 2: Prevalence and infection intensity profile for soil-transmitted helminth infection

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Risk factors of soil-transmitted helminth infections

The risk factors associated with STH in relation to sociodemographic, behavioral, and environment were examined by the bivariate and multivariable logistic regression analysis [Table 1]. Poor handwashing (without soap) practices after defecation in school (odds ratio [OR] = 4.06; 95% CI = 2.37–6.96) and irregular hand wash before meal (OR = 4.80;95% CI = 2.78–8.30) were two significant factors for STH. Other behavioral factors which had significant association were pica (OR = 11.24; 95%CI = 3.88–32.55) and barefoot walking (OR = 3.06; 95% CI = 1.47–6.37). Untrimmed nails (OR = 3.32; 95% CI = 1.82–6.05), poor hygiene (OR = 3.76; 95% CI = 2.05–6.91; P < 0.001), and lack of de-worming (never or more than 1 year since last dose) (OR = 4.62; 95% CI = 1.95–10.92) were also found to have significantly associated. Of the environmental factors, overcrowding (OR = 1.83; 95% CI = 1.02–3.27), garbage disposal in community bin (OR = 2.33; 95% CI = 1.20–4.52), absence of cooking slab (OR = 5.82; 95% CI = 1.29–26.35), and more than 100 meters distance of playground from home (OR = 3.00; 95% CI = 1.48–6.1) were also significantly associated with STH infection.

All the risk factors which had statistical significance of 0.1 on bivariate analysis were included in the multivariable logistic regression analysis, and the results for the same was given as adjusted OR which confirmed that children who had poor handwashing behavior in school after toilet use were 2.34 times at risk of STH infection (95% CI = 1.17–4.7), who were irregular in handwashing before eating had 2.29 times risk of STH infection (95% CI = 1.1–4.82), had pica behavior were at 8.23 times more at risk of STH infection (95% CI = 2.57–26.34), and who had lack of de-worming (never been de-wormed or de-wormed more than 1 year back) were 3.42 times (95% CI = 1.25–9.36), more likely to suffer from STH infection, respectively [Table 1].

   Discussion Top

The tropical climatic conditions of India together with unhealthy socio-behavioral habits due to poverty and poor personal and environmental hygiene prevailing in various parts of our country contribute highly to the spread of the STH infections. The overall prevalence of STH infection was found to be 54.8% in our study which was comparable to the prevalence reported by Kumar et al.[13] and Greenland et al.[14] However, lower prevalence was reported in a study in Delhi by Ranjan et al.[10] This was probably due to the difference in study setting as the present study was conducted in an urban resettlement colony which also had slum clusters and poor sanitation and hygienic conditions in the community, whereas Ranjan et al.[10] did the study in MCD schools of Shahadra.

While analyzing the risk factors, we found in our study that the behavior, hygiene, and environment played an important role in STH infection, especially handwashing behavior and de-worming status. These findings have been corroborated by various studies conducted in India[10],[14],[15] and other places.[16],[17] Mass de-worming was started in Delhi in year 2013 and was predominantly in government schools. In year 2017, biannual de-worming was started in all over India including Delhi. The importance of biannual de-worming is also reflected in our study as significantly higher odds of STH was found in children who were never de-wormed or de-wormed more than 1 year back since the time of interview in comparison to those who were de-wormed within 6 months preceding the time of interview.

Handwashing practice was identified as one of the important risk factors for the STH infection. It includes handwashing in school with soap and water and also always washing hands before eating which had lower odds of STH, as shown in our study. This has been recognized in many of the studies such as by Greenland et al.[14] in Bihar and Tefera et al.[18] in South west Ethiopia and also correlate with the transmission cycle of STH infection by feco-oral route through contaminated hands.

Pica was found to be have significantly higher risk of STH infection on univariate and multivariate logistic analysis which is supported by the fact that soil is the source of helminths in STH infection. Similar finding was reported in the study conducted by Kalliappan et al.[15]

Other behavioral factors such as bare foot walking were not found to be significant on the multivariate analysis in our study. Similar findings were reported in studies conducted by Wang et al.,[16] Worrell et al.,[19] Liu et al.,[20] Davis et al.,[21] and Suchdev et al.[22] In studies by Garn et al.[23] and Freeman et al.,[24] barefoot walking was significantly associated to hookworm infection in these studies.

In the present study, on multivariate logistic regression analysis, both nail hygiene and personal hygiene were found to be nonsignificant. Similar results on multivariate analysis were found in few studies.[15],[18],[25],[26] However, Abera et al.[27] in their study found fingernail status to be significantly associated with Intestinal helminths which can be explained by the fact that in this study besides STH other intestinal helminths such as Taenia, Schistosoma mansoni, Hymenolepis nana, and Enterobius vermicularis were included.

In our study, out of the environmental factors studied overcrowding, presence of kitchen slab, garbage disposal place, distance of playground, and community bin from house were found to be statistically significant. However, on multivariate logistic regression analysis, all of them were found to be nonsignificant. In the studies conducted by Kaliappan et al.[15] and Worrell et al.,[19] there was no statistically significant association between STH infections and overcrowding, whereas Staudacher et al.[28] reported that there was less odds of STH infection if the garbage dumping place was more than 100 meters away from households. Our study has not shown such association probably because our study was carried out in an urban resettlement colony with community dustbin within 100 meters of majority of household's while the other study was carried out in schools where study subjects belonged to different residential settings.

At the beginning of our study, in February 2016, mass de-worming was carried out in Delhi in government schools. There could be a possibility of a recall bias regarding de-worming status when comparing study subjects going to government and private schools and also in those subjects who were interviewed in the later part of the year in 2016. Handwashing practices were self-reported. Hence, it is possible that the frequency of “good practices” have been over reported. Another limitation is taking a single stool sample for the study. It may underestimate STH prevalence, especially of hook worm infection which was not found in our study. Since the conduct of this study four rounds of biannual deworming has been carried in government schools and aganwadis. Hence, the results of this study should be interpreted with caution keeping this in mind.

   Conclusion Top

Alarmingly high prevalence of STH in the urban resettlement colony of Delhi emphasizes biannual de-worming in the area in tune with the WHO recommendations,[1] which the Government of Delhi started in 2017. Several significant behavioral, environmental, and personal hygiene-related risk factors for STH infection as revealed in the study highlight the need for comprehensive IEC-BCC activities at family, community and also in schools.

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Conflicts of interest

There are no conflicts of interest.

   References Top

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  [Table 1], [Table 2]

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