Prevalence & determinants of soil-transmitted helminth infection among 1-15 year-olds in a tribal-dominated district of Odisha, India

Materials & Methods

This cross-sectional study was conducted by the department of Epidemiology, Indian Council of Medical Research-Regional Regional Medical Research Centre (ICMR-RMRC), Bhubaneswar, Odisha, India. The study was started after obtaining the ethical clearance by the Institutional Ethics Committee of ICMR-RMRC.

Results

The mean age (± standard deviation) of the 1927 children recruited with stool examination in this study was 6.46 (±3.25) yr. Males comprised slightly more than half of the population (50.4%). In terms of socio-demographic categories, participants from Scheduled Castes (SC) made up the largest group, 47.8 per cent, Scheduled Tribes (ST) at 31.3 per cent, followed by Other Backward Classes (OBC) at 15.9 per cent. The majority of the participants were from nuclear families (81.2%), and 56.8 per cent were attending school. About 82 per cent of participants aged more than five years practised open defecation, while 82.3 per cent adhered to regular handwashing. Thirteen per cent of the recruited children (255/1927; 13.2%) were found to be STH positive, with a mean age of 6.5 (±3.29) years, and 44.8% were girls. School-going children (6–15 yr) showed a higher prevalence (15.53%) compared to younger (1-5 yr) ones (9.7%), which was statistically significant.

The detailed information about socio-demographic characteristics, Water, Sanitation, and Hygiene (WASH) practices, open defecation status and ALB consumption in the last six months are presented in table IIA. Upon assessing the cognitive status of study participants using VSMS test and evaluating the (IQ) score, the majority (91%) scored as average, followed by low average (8.15%) and no statistically significant association was found between STH positivity and cognitive status (Table IIB). The detailed information about socio-demographic characteristics, WASH practices, open defecation status and ALB consumption in the last six months are presented in table IIA. The geographical distribution of the study participants (blocks and clusters) is depicted in figure 1. The distribution of study participants and their STH positivity are presented in figure 2 (supplementary file).

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Fig. 1.

The map shows. Nabarangpur district and its block boundaries. The administrative map, obtained from the Survey of India office, was georeferenced to ensure spatial accuracy. All map production and digitization were carried out in-house as part of our project development efforts. Source: QGIS Software 3.4 (Open Source Software).

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Fig. 2.

Heat map showing block wise STH positive cases in Nabarangapur district of Odisha. Source: QGIS Software 3.4 (Open Source Software).

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The overall prevalence of STH infection among the study children was found to be 13.2 per cent. The prevalence of STH infection among boys and girls was 14.6 per cent and 11.8 per cent respectively and no statistically significant difference was found. The presence of STH infection among children practising open defecation was found to be high (18.29%) compared to children using toilet facilities (5%), and this difference was found to be statistically significant (P<0.01).

Among the study children, 34.4 per cent were stunted, 19.6 per cent had wasting, and 23.1 per cent were underweight. While a significant association was found between STH infection and wasting (P =0.05), no strong association was observed between STH positivity and stunting, underweight, or acute malnutrition. The detailed anthropometric indices, nutritional status and STH infection are depicted in (Table III)².

Among the 255 STH positive samples, hookworm was found to be the most common infection, with a prevalence of 71.3 per cent, followed by A. lumbricoides, having a prevalence 28.2 per cent. None was found to be infected with T. trichiura. Only one child (0.4%) was found to be infected with both hookworm and A. lumbricoides. The infection intensity was determined based on the helminthic egg count. For A. lumbricoides, egg count ranges 1-4999, 5000– 49999, and ≥50000 were considered as mild, moderate and severe intensity, respectively. Similarly, for hookworm, egg counts ranging from 1-1999, 2000-3999,and ≥4000 were considered as mild, moderate and severe intensity, respectively¹⁷. Among the STH-positive children, the majority (90.5%) had mild infection followed by 4.7 per cent with moderate and 4.3 per cent with severe infection. The detailed status of different helminth infections including their intensity of infection is depicted in table IV.

Table V presents the results of unadjusted and adjusted logistic regression analyses on factors associated with STH infection. In the unadjusted analysis, children aged 1-5 yr had significantly lower odds of STH infection than those aged 6-15 yr (OR = 0.57, 95 per cent CI: 0.43-0.75, P<0.001). However, age was excluded from the adjusted model since only children above five years were analysed to consider hygiene factors like open defecation and handwashing. Handwashing after defecation was a strong protective factor, reducing the odds of infection by 85 per cent (OR = 0.15, 95% CI: 0.05-0.47, P = 0.001). However, it was not included in the adjusted model due to collinearity.

Taking ALB in the past six months significantly lowered the risk of STH infection in both unadjusted (OR = 0.61, 95% CI: 0.37-1.02, P = 0.059) and adjusted analyses (OR = 0.56, 95% CI: 0.32-0.98, P = 0.041), highlighting its effectiveness as a deworming treatment.

Discussion

This study, conducted in Eastern India among children aged 1-15 in a tribal district, revealed a widespread prevalence of STH. Worldwide, the majority of STH cases are caused by two primary parasites: A. lumbricoides and T. trichiura, followed by hookworm infections¹⁸. In this study, the most common STH infections were hookworm (HW) and roundworm (RW; A. lumbricoides), with no case of whipworm (T. trichiura) found among the study participants. The overall prevalence of STH was 13.2 per cent, closely aligning with the findings of Kattula et al¹⁹, who reported a range of 5.9-12.1 per cent in rural areas. Furthermore, the prevalence of hookworm infections was higher (9.5%) than that of Ascaris infections (3.8%), consistent with other studies showing a higher prevalence of hookworm compared to Ascaris infections²⁰. The predominance of hookworm infections over other STH in our study could be due to geo-environmental factors and occupational practices. The absence of T. trichiura suggests its limited presence in this setting, supporting findings from similar research²¹. Moreover, other studies have also shown that Ascaris and Trichuris are more common in urban areas, whereas hookworm predominantly affects rural children²².

This study found that STH infections were more prevalent among males (14.6%), likely due to their increased exposure to infected soil when accompanying their fathers to fields or engaging in outdoor activities²³. School-aged children (6-15 yr) had a higher prevalence (15.53%) than preschool-aged children (9.7%), which is consistent with the findings of Avhad²⁴ and Greenland et al²⁵, who attributed this to greater exposure to contaminated environments and poorer hygiene practices among older children. However, Awasthi et al²⁶ reported a significantly higher prevalence (65.9%) in preschool children in rural Uttar Pradesh, a region where open defecation contributed to the spread of STH infections. The strong link between open defecation and STH was evident in this study, with a prevalence of 18.3 per cent among children practicing open defecation, compared to 5 per cent among those using toilets. The Swachh Bharat Mission might have contributed to improved sanitation, as 92.4 per cent of families in the study reported using household toilets, a stark contrast with the findings from earlier surveys²⁷. Nonetheless, persistent open defecation remains a challenge, underscoring the need for ongoing sanitation initiatives²⁸. Hand washing practices also play a crucial role in STH transmission, with children who did not use soap after defecation being at significantly higher risk of infection. This finding echoed the results from other studies which showed that poor hand hygiene was associated with STH risk²⁹. The use of sanitation facilities and regular shoe-wearing reduced infection risk, though Kaliappan et al³⁰ did not find a strong link between inconsistent shoe-wearing and increased STH risk.

Anthelminthic treatments, such as a single dose of albendazole, have proven effective in treating A. lumbricoides and hookworm, with cure rates of 88per cent and 78 per cent, respectively³¹. Regular MDA programs have demonstrated success, with a study in southern India reporting a 77 per cent reduction in STH burden following regular deworming³². However, challenges persist, as evidenced by a study in Odisha, where nearly 50 per cent of children in urban slums remained infected after deworming¹². While deworming improves growth outcomes in infected children, its impact on broader health markers, such as cognitive development or school attendance, is limited according to a Cochrane review of 41 trials³³.

The link between STH infections and malnutrition is well-documented, with wasting found significantly associated with infection in this study (P=0.05), mirroring the findings from Geleto et al³⁴ and Dhaka et al²⁸. Although no significant association was found between STH infection and stunting or underweight, the higher burden of infection among malnourished children was concerning, as malnutrition can both result from and exacerbate parasitic infections³⁵. Malnutrition and nutritional deficiencies can result from reduced appetite, poor nutrient intake, impaired absorption, increased nutrient loss, and altered metabolism³⁶. Combining deworming with vitamin A supplementation has been shown to reduce Ascaris reinfection rates³⁵, though the DEVTA study found no significant improvements in weight, haemoglobin, or mortality rates³⁷. Long-term STH control will require a comprehensive approach addressing sanitation, hygiene, and malnutrition.

While this study provided important insights, there are some limitations that should be considered when interpreting the results. This study is one of the few to focus on STH prevalence in a tribal-dominated region, offering valuable insights into an underrepresented population. Its strengths include a large sample size, random cluster selection, and standardized methods for data collection and laboratory analysis, enhancing the reliability of the findings. While the study is limited to a single district in Odisha, which may slightly restrict the generalizability of the results, it still provides crucial data for similar regions. The 16.9 per cent dropout rate was unlikely to significantly impact the overall findings, as the sample remained robust and representative.

Considering the above findings and their implications, the study concludes that there is a noteworthy prevalence of helminth infection, at 13.2 per cent among the children (1-15 yr) in a tribal area. The STH prevalence data from this cross-sectional investigation, conducted in several blocks of the Odisha district of Nabarangapur, served as the basis for this research. Age-related increase in prevalence suggested that recurrent infections had a cumulative effect. These findings highlight the necessity of focused and integrated public health initiatives to control and prevent helminth infection, especially among children of rural and tribal areas. Comprehensive control measures, such as mass medicine administration, access to clean and safe drinking water and sanitation, and health education campaigns around good hygiene habits, are essential to counteract the detrimental consequences of helminth infections. Ensuring the implementation of ongoing public health programs, including school health programs and their better coverage, would help to prevent the helminth infections and ensure the well-being of the children.