A coprological survey for assessing intensity of parasitic infection in school children: Cross-sectional study.

BACKGROUND: Intestinal parasitic infections (IPIs) are endemic worldwide and have been the cause of illness and disease worldwide.
OBJECTIVES: The study is aimed to estimate prevalence, intensity, and factors associated with IPIs among school children aged 6-12 years.
MATERIALS AND METHODS: This cross-sectional survey was carried out from February to July 2010, in the diagnostic laboratory of Microbiology department. The study group was divided into four groups, namely, Group A; Group B; Group C; and Group D. A total of 1769 eligible children were enrolled for sampling from these schools. For each enrolled child in the study, a standard stool ova and parasite test with formol-ether concentration technique was done for the assessment of the outcome.
RESULTS: Among 1224 participants, 714 (58.3%) were boys and 508 (41.5%) were girls. The overall prevalence of IPIs was estimated as 51.5%. Group A 84%, Group B 64.7%, Group C 62.4%, and Group D 39.3%. Single IPIs were 65.7%, among which 48% were helminthic and 19.3% were protozoan. Multiple IPIs were 34.2%, among which protozoan along with helminthic were 25.9%, polyhelminthic were 8.5% and polyprotozoan were 4.2%. Among the IPIs detected, overall prevalence of helminth was 75.9%, protozoan was 24.1%. Among the helminthes hookworm was highest (28%). Among the protozoan Entamoeba histolytica/dispar was highest (14.8%).
CONCLUSIONS: The study confirmed that prevalence of IPIs is high as 51.5%. Overall prevalence shows an endemic situation. Therefore, it is recommended that local health sectors should make provision for regular examination of parasitosis and deworming.

INTRODUCTION

Intestinal parasitic infections (IPIs) are endemic worldwide and considered as the cause of illness and disease. It is estimated to affect around 3.5 billion people globally; 300 million are ill, 50% of them being school-age children.[1]

The survey was conducted in school children as they have great impact on parasite control in future. A prevalence survey of IPIs in different regions is a prerequisite for developing control strategies. Considering this and the paucity of information available on the prevalence of IPIs, the present study was undertaken to estimate IPIs among school children and to assess epidemiologic factors associated.

MATERIALS AND METHODS

Study design and setting

This cross-sectional survey was carried out from February to July 2010, in the diagnostic laboratory of microbiology department.

Study population, sample size, and sampling strategy

The study population consisted of school children from 6 to 12 years of age enrolled in various schools of Chitradurga. The sample size was calculated for the primary objective taking the prevalence to be 50% that gives the maximum sample size, with 95% level of confidence and 5% bound on the error of estimation. The minimum sample size required was 400 children. A list of all schools (the sampling frame) in the locality was prepared. They were divided into four groups, namely, Group A (orphanage); Group B (residential schools); Group C (government schools); and Group D (private schools). Simple random sampling method was employed to select 1 school from each group of schools.

A total of 1769 eligible children were enrolled for sampling from these schools. Out of these, 1224 stool samples were received giving the response rate of 69.1%.

Data collection

The outcome variable was stool parasite status of the received sample, whether positive or negative for any intestinal parasite, which was determined from a stool sample. Data on the independent variable of socio-demographic characteristics were collected by trained research officers on a pretested and structured questionnaire addressed to the student.

Stool sample collection and laboratory testing

For each enrolled child in the study, a standard stool ova and parasite test with 1 concentration technique was done for the assessment of the outcome[2] the test was conducted at diagnostic microbiology laboratory, by the principal investigator and co-investigator with the help of an experienced laboratory technician. At the time of interview, the students were given a dry, clean, leak proof container labeled with name and identification number for the collection of stool sample the next day. The students were provided written guidelines for the method of collection of the sample, addressed to their caretaker.

In the laboratory, slides were then prepared directly for wet mount in saline as well as in Lugol's iodine and then were microscopically examined initially under low power (10×=100 times magnification) bright field then under high power (40× = 400 times magnification) bright field. Finally the sample was concentrated applying the formol–ether technique[3] and again iodine stained slides were prepared and examined microscopically.

Ethical considerations

The protocol for this study was approved from the Chairman, and the secretary, institutional ethical committee (IEC). The approval was on the agreement that patient anonymity must be maintained, good laboratory practice quality control ensured, and that every finding would be treated with utmost confidentiality and for the purpose of this research only, all work was performed according to the international guidelines for human experimentation in biomedical research.[4] Approval was obtained from the Head Master of each school studied and informed consent was obtained from each of the participating pupils. The participating students were given chocolates as an incentive. Infected pupils were referred to the primary health center in the area for immediate treatment.

Data management and statistical analysis

During data collection completed questionnaires were checked regularly to rectify any discrepancy, logical errors, or missing values. The data entry was carried out using Microsoft Office Excel worksheet and then the data were exported to statistical analysis software WINK SDA for further analysis. Variables were categorized in a biologically meaningful way where applicable.

To the analyzed data, mean and standard deviation for continuous variables and proportion for categorical variables were computed. Crude associations of the binary outcome variable with each independent variable were assessed by Chi-square test. The level of statistical significance was set as P≤0.05 and for each statistically significant factor.

Results

The results represent information collected from 1224 stool samples.

Descriptive characteristics

Among 1224 participants, 714 (58.3%) were boys and 508 (41.5%) were girls.

Prevalence of intestinal parasitic infections

The overall prevalence of IPIs was estimated as 51.5% (631/1224) [Table 1]. Group A 84% (62/73), Group B 64.7% (88/136), Group C 62.4% (221/354), and Group D 39.3% (260/661). Higher prevalence was found in 6-10 years aged; the prevalence percentage declined with increase in age and showed lowest prevalence in participants above 12 years of age. The prevalence was higher in boys as compared with girls [Tables 2–5].

Table 1

Prevalence of IPIs among different groups

Table 2

Prevalence of IPIs among different age groups in Group A

Table 5

Prevalence of IPIs among different age groups in Group D

Intensity of infection

Single IPIs were 65.7%, among which 48% were helminthic and 19.3% were protozoan. Multiple IPIs were 34.2%, among which protozoan were 4.2%, helminthic were 8.5%, and protozoan along with helminthic were 25.9% [Table 6]. Among the IPIs detected, overall prevalence of helminth was 75.9%, protozoan was 24.1%. Among the helminths hookworm was highest (28%) followed by Ascaris lumbricoides (20.1%), Enterobius vermicularis (16.1%), Trichuris trichuria (6.3%), Taenia spp. (3.3%) and others (1.9%), respectively. Among the protozoan Entamoeba histolytica/dispar was highest (14.8%) followed by Giardia intestinalis (6.3%) and others (2.8%) [Table 7]. Highest helminthic infection (79%) was found among Group A and lowest (73.8%) in Group B. The factors associated with the IPIs were estimated as in Table 8.

Table 6

Different types of IPIs in school children

Table 7

Intensity/load of IPIs among various study groups

Table 8

Factors associated with prevalence of IPIs

DISCUSSION

We have estimated the prevalence and factors associated with IPIs among school children aged 6-12 years from various schools. This study showed that age, sex, residence, water source, defecation site, personal hygiene, and caretaker were significantly associated with IPIs. The prevalence of IPIs was estimated to be 51.5% and such high prevalence has been consistently reported by a number of similar demographic studies conducted.[156789] The other Indian studies have reported prevalence ranging from 7.5% to 15.5% in Chandigarh (2000), 46.5% in Delhi (2002), 47.1% in Andhra Pradesh (1981), 73.4% in Tamil Nadu (1995), 70.8% and 60% in Gujarat (1981).[7] In this study IPIs namely Hookworm, A.lumbricoides, E.vermicularis, T. trichuria, E. histolytica/dispar, G. intestinalis and other spp. were identified from the stool samples.

Our study detected helminthic IPIs (75.9%) and protozoan IPIs (24.1%), this is in agreement with a previous study by Sharma et al.[1] However Wani et al. have reported different intensities of IPIs.[10]

The reported prevalence of polyparasitism elsewhere varies from 4.3% to as high as 72.7%.[11]

In our study, multiple IPIs detected were 34.2%, which is close to the findings by Sherchand et al. of 28.9%, and is different from other reports.[15612] This is a clear indication of large number of various species of parasites in the local community.

In our study, hookworm IPIs were estimated to be up to 28%, which is in correlation with Sharma et al.[1] However, other studies have reported lower prevalence of 4.44%[6] and 6.4%.[5]

In the present study, we detected A. lumbricoides IPIs of 20.1%, which is in range with other studies 28.4%,[8] 26.3%,[5] 16.5%,[12] 14.22%,[6] and 13.8%;[1] however, other studies have reported high prevalence of 71.58%,[5] 71%,[9] 68.3%[13] and low prevalence of 0.8%.[14]

In the present study, E. histolytica/dispar IPIs was 14.8%, which is comparable with Wani et al. 11%,[10] whereas other studies have reported 27.7%,[15] 6.22%,[11] 6.1%,[1] and 0.8%.[16] G. intestinalis was found to be 6.3% which is in correlation with 5.7%,[1] 7.2%,[10] and 9.33%,[11] whereas other studies have reported high prevalence rate of 11%,[14] 25.3%,[17] 28,9%,[18] highest of 67.7%[15] and low prevalence of 3.2%.[16]

Transmissions of IPIs are generally more in orphanage, minority hostels, and suburban government schools than private schools. This could be related to the poor sanitary conditions and contaminated water supplies.

Age is an important risk factor for IPIs[19] and preschool and school going children have been reported to be at highest risk for IPIs.[3] In our study, 6-10 year olds showed higher intensity of IPIs, whereas it decreased with increase in age, and this could be due to the fact that as children grow older they follow better hygienic practices. The linear association of age needs further exploration through prospective studies.

Other factors such as lack of access to clean water, lack of access to proper care and overcrowded conditions[1014] may also be significantly associated.

The variations in the prevalence of IPIs in different studies could be attributed to the time of study and geographical differences in the area.

Strength and limitations

As per our knowledge this study is first of its kind in our locality focusing on school children of different living conditions. The stool sample testing by routine ova and parasite method and a concentration technique increased the validity of estimates.

Our study has certain limitations that need to be considered while interpreting results. The response rate was lower than expected (69.1%) limiting the number of samples obtained.

We conducted single stool examination for detection of IPIs, which could have underestimated the prevalence, as optimal laboratory diagnosis of IPIs requires the examination of at least three stool specimens collected over several days. More recent studies have suggested that 1 or 2 stool samples will detect up to 90% of the protozoa present.[1215]

It was planned to conduct stool sample testing within 2 h of collection, however, due to logistic constraints, it was delayed at times from 3 to 6 h as a result of which we could not detect the invasive protozoa, that is, the trophozoites. The other limitation that we would like to mention is due to the constraints mentioned above and the technique we used was only light microscopy and it is quite possible that we have either missed or misinterpreted Entamoeba moshkovskii.

We cannot draw conclusions on the association of different factors with IPIs as this is a limitation in cross sectional study design.

CONCLUSION

IPIs are highly prevalent in this setting. Poor hygienic practices are important factors associated with IPIs. Age is also an important predicator of IPIs in 6-12 year old school children. There is a need to promote mass scale deworming and health promotion campaigns to create awareness about health and hygiene.

Although we have correlated our results to different reports, we could not find such reports from this geographical study area. Hence we here by indicate that such prevalence studies are highly recommended from this area.

Table 3

Prevalence of IPIs among different age groups in Group B

Table 4

Prevalence of IPIs among different age groups in Group C