The disease burden of soil-transmitted helminthiasis (STH) is greatly felt worldwide as suggested by some available data, prominently in both temperate and tropical regions. Ascaris lumbricoides, one of the important causes of STH infections in humans particularly in children, is the largest nematode that infects the intestinal tract of humans and is the most common of the intestinal roundworms infecting an estimated 1.3 billion individuals in the Asia Pacific Region, 478 million of which are children (Cromptom, D.W., 1999)1. Among the estimated 1.3 billion individuals infected, at least 20,000 die annually, mostly young children. High prevalence of Ascariasis is closely associated with poverty, poor environmental hygiene including poor sanitation wherein there is an improper disposal of feces, contaminated food, inadequate personal hygiene and lack of health services. It is also generally associated with areas that are basically warm, agricultural and low on the economic and human development scale.
Vitamin A deficiency (VAD) affects an estimate of 140 - 250 million children under five years of age. In 1995 it was estimated that VAD affected over two million preschool children in Asia Pacific countries. It has been recognized for decades as the leading cause of preventable childhood blindness in developing countries. In addition, for children with vitamin A deficiency, the risk of dying from diarrhea, measles and malaria is increased by 20% - 24%. Vitamin A deficiency in children also leads to retarded physical growth and development.
The problems of vitamin A deficiency and Ascariasis are recognized to coexist in children facing socio-economic difficulty. Both these diseases affect the outcomes of the treatments but most studies deal with effect of Ascariasis on the absorption of vitamin A. Little is known about the preventive aspects of vitamin A supplementation on Ascariasis after deworming.
In the Philippines, statistics and data on the mortality and morbidity of Ascariasis is limited, but in a survey conducted in residential institutions in Metro Manila regarding intestinal parasites in children, Ascaris infection has a 36.0% prevalence rate (Belizario, et al)2. The Department of Health launched the program Garantisadong Pambata to address this problem. It is a bi-annual activity which aims to increase public awareness on the different services focusing on both mother and child. Workers also tour the community, giving both Albendazole at 400mg/tab preparation and Vitamin A 200,000 IU to children from 6-71 months old. Eventually, it is hoped that childhood illnesses and deaths will be reduced and positive child care behaviors will be promoted.
Since children less than five years of age suffer the greatest morbidity when infected with Ascaris. Children 6-12 years old harbor the greatest load of infection and are the significant sources of transmission.
This community-based case-control study will inquire if Vitamin A supplementation is effective in reducing Ascariasis infection. It will try to determine if there is an association between the exposure to Vitamin A and Ascariasis infection as the disease outcome among children 2 to 6 years old in Parañaque City. Children positive with Ascariasis infection, has not taken any deworming medication since the last Garantisadong Pambata, and who lives in Parañaque City will be the case. While the control, are those who resulted to negative fecalysis result in Ascariasis infection and has the same characteristics as stipulated above.
Significance of the Study
If can be proven that Vitamin A supplementation is preventive of occurrence of ascariasis infection, the importance of its supplementation can be recommended to medical practitioners, as well as to the Department of Health who is implementing the Garantisadong Pambata Program. This can further be translated or integrated into the primary health care units of the Department. Moreover, strict implementation and strengthening of vitamin A supplementation program can be done.
Another practical value of the study is for the private medical practitioners to incorporate the Vitamin A Supplementation during deworming of their patients.
Review of Related Literature
Vitamin A deficiency and helminthiasis continuous to be a public health problem especially in developing countries. Their prevalences have been highly correlated in these countries, since both diseases burden these endemic countries, although their interaction is still debated3 and most studies prove to be inconclusive. Mass prophylaxis of the vitamin A supplementation and administration of anti-helmintic drugs proved to be an effective public health intervention that reduces parasite burden and substantially improves the nutritional status of children. Besides, the target groups for these two interventions are of the same age. It is then more logical and practical to combine deworming with vitamin A supplementation.4 This is the reason why the WHO encourages the administration of the vitamin A and deworming drugs be given simultaneously.
According to a study in Panama,5 it was proven that vitamin A supplementation was a significant predictor of lower Ascaris intensity before and 3 months after deworming. Also, the timing of deworming, relative to vitamin A supplementation, is critical to achieving maximum benefit against Ascaris infection, especially in stunted children. However, more studies are needed to associate vitamin A supplementation with the delayed rate of reinfection with Ascariasis.
In another study, vitamin A supplementation was found out that it may reverse post-operative immunosuppression and boost immune responses in the elderly, persons with parasitic infections, and persons with a high exposure to ultraviolet light. Moreover, animal work suggests that it may enhance responses to weak immunogens and reverse immunosuppression.10
A number of researches suggest that vitamin A supplementation have distinct effects on the innate and adaptive immune responses that are important in protecting against parasitic infections. Vitamin A was observed to have caused upregulation of the T-helper type 2 (Th2) humoral response and downregulation of the T-helper type 1 (Th1) cellular response. This upregulation may lead to greater immunoglobulin E-mediated expulsion of helminths.9 Some findings of the study even appear to strengthen the cause-effect association found between vitamin A supplementation on infected children as compared to its effect among uninfected children. The same study concluded that vitamin A has a differential regulatory effect on the fecal cytokine response but that this effect is conditioned by the presence or absence of the pathogen infecting a child, the type of pathogen, and the onset of the disease process. This might be a potential reason why previous studies reported different health outcomes as a result of vitamin A supplementation. Thus, further work is needed to confirm that vitamin A has this differential effect on the immune response of the infected individual, and eventually, on the immune response against parasitic infections, particularly on Ascariasis.
Table 1. Results from studies determining the association between vitamin A supplementation and Ascariasis
Authors and Year
Outcome
Study Design / Area / Subjects
Results
Limitations
Payne L. G., Koski K. G., et. al. 2007
Ascariasis reinfection
Prospective community based study; Bocas del Toro, Panama; 595 Ngobe children aged from 12-60 months
Reinfection rates with Ascaris were decreased 3 mos after supplementation but not after 5 mos.
More research on stunted children need to be done
Long, K. Z., Rosado, J. L., et. al. 2007
Gastrointestinal Parasitic Infections
Double blind, randomized, clinical trial; La Magdalena Atlicpac, Mexico; 786 children aged 6-15 months
Vit. A + Zn decreased Giardia infections while increased Ascaris infections.
Vit. A and Zn have more heterogenous effects in different subgroups of culture
Results are not clear on the effect of Vitamin A and Zinc on Ascaris and Ascaris related diarrheal episodes.
Long, K. Z., Santos, J. I., et. al. 2006.
Intestinal Immune Response
Randomized, placebo controlled double blind trial; La Magdalena Atlicpac, Mexico; 200 children bet. the ages 5 and 15 months
Vit A supplementation reduces levels of the chemokine MCP-1 in stools collected from children during the diarrheal disease season
Conceptual Framework
Household Size
Socio-Economic Status
Education of the Caregiver
Age
Nutritional Status
Albendazole
Vitamin A Supplementation
Ascariasis reinfection
Based on related readings, we have formulated a schematic diagram of the causal pathway that leads to Ascariasis reinfection (outcome or dependent variable) from the effect of vitamin A supplementation (factor or independent variable) administered together with Albendazole, the anti-helminthic drug given among preschool children. We have identified 5 confounding factors that are risk factors for Ascariasis and which are also associated with vitamin A supplementation. These can be seen on the lower half of the conceptual framework. The first of which is nutrition status, which is the classification given to a child according to his/her weight for age as determined from the weight-for-age standards for Filipino children. Since nutrition status directly affects the body's defenses, a child who may be underweight may have increased susceptibility to infections, including Ascariasis. Age is also identified as a potential confounder since preschool children (aged below 6 years old) are more prone to parasitic infections because of their unhygienic playing habits and practices. The education of the caregiver may also lead to the development of Ascariasis such that lack of knowledge in sanitation and clean practices may predispose to a higher risk of exposure to infection. Knowledge on the sources of infection, modes of transmission, points of entry and exit of pathogens may be lacking in caretakers who have low educational status. Low education status also affects the choice of food among these caretakers. As a result, they may feed their children with diet lacking essential nutrients (especially vitamin A) that may lead to greater vulnerability to Ascaris infection. Socio-Economic status is also associated with Ascariasis, in a sense that higher rates of infection are more common among the poor than among those who are better off. The urban-poor, in particular, are more exposed to environmental factors that may lead to Ascariasis, such as contact to dirty soil around the house which may harbor Ascaris ova. These infect a person when he/she accidentally ingests these eggs through unsanitary behaviors and practices. More so, having low income may force a household to buy cheap foods that are lacking in vitamins and minerals, and hence, a low nutrition status for the children. A large household size is often a factor for crowding and congestion inside the house that would allow transfer of parasites and pathogens among the household members. Oftentimes, large households have small houses, and hence, children tend to play outside the house barefooted where there is a greater risk of contacting Ascaris eggs. In addition to this, foods served in large households are most likely scarce, and thus children may not receive enough nutrients.
Research Hypothesis:
Vitamin A together with Albendazole is effective in reducing Ascaris reinfection among preschool children (3 to 6 years of age) 6 months after its supplementation
General Objective:
To determine the association between vitamin A and Ascariasis reinfection among preschool children (3 to 6 years of age) in Parañaque City.
Specific Objectives:
What is the proportion of subjects who were given Vitamin A supplementation and Albendazole who were infected with Ascariasis?
What is the proportion of subjects given Vitamin A supplementation and Albendazole without infection from ascariasis?
To compare the proportions of infection with ascariasis between those who were given Vitamin A supplementation and those who were not given vitamin A supplementation.
To determine the effect of the probable confounders in the association of vitamin A supplementation and Ascariasis such as:
Age
Household Size
Education status of the Caregiver
Socio-Economic Status
Nutrition Status
To determine if there are effect measure modifiers in the study
Research Methodology:
Summary of Methodology
A population-based case control study will be conducted to determine the possible relationship between Vitamin A and ascariasis infection. We will be comparing 1,350 cases aged 2 to 6 years who will be diagnosed with ascariasis infection against 1,350 controls without ascariasis infection (see computation below). Both cases and controls are residing in Paranaque City and will be selected 6 months after deworming during the the Garantisadong Pambata campaign last October 2009.
Research Design
Selection of research strategies
A case-control design will be employed in this study. The selected cases and controls will be interviewed by a trained interviewer using a pre-structured questionnaire.
Selection of research setting and subjects
Subjects for this study will be recruited in the 16 barangays of Paranaque City. Subjects will be children aged 2 to 6 years dewormed last October, 2009 during the Garantisadong Pambata campaign of the Department of Health. A subject will be eligible as a case if he/she will be found positive for worm or ova during routine fecalysis. Controls will be those found negative for worm or ova during routine fecalysis. To ensure that ascariasis will be diagnosed uniformly, the original slide will be read by 2 other medical technologist who will be blinded of the diagnosis. A positive result from at least 2 slides will be considered as positive. Study period will be from October 2009 to March 2010.
Sampling
To ensure necessary number of samples, sample size was computed using Logistic Regression Method with 90 % level of significance and 56% prevalence of Ascariasis in children without vitamin A supplementation and 49 % prevalence in those without Supplementation. Samples (cases and controls) will be selected randomly using table of random numbers from a master list of children aged 2 to 6 per barangay with probability proportionate to size/population of the barangays.
Assumptions:
Level of significance = 0.10; Power = 0.80
Proportion of preschool children with Ascariasis without vitamin A Supplementation = 56% or 0.56 (Payne, et.al, 2007)
Proportion of preschool children with Ascariasis with vitamin A Supplementation = 49% or 0.49 (Payne, et.al, 2007)
Difference between two proportions = 52.5% or 0.525
Significant standard deviation = 0.05
Formula:
Therefore, every group must have at least 1,227 samples. To account for the non-responders among the samples, 10% of the minimum sample size will be added. Thus, giving a total of 1,350 samples (1,227 + 122.7) for both the cases and the controls.
Use of Controls
There will be 1 control for every case identified in the study. The diagnosis of controls will be based on a negative result on routine fecalysis.
Study instrument
The questionnaire will be constructed to minimize interviewer and respondent bias. Information included in the questionnaire will be: 1)age nutrition status,2) level of education of caregiver, 3) economic status,4) household size,5) vitamin A and Albendazole supplementation, 6) result of fecalysis. A calibrated salter scale will be used for measuring weights of the children.
Operational definitions (to follow):
Nutrition status
Level of education
Economic status
Household size
Vitamin A supplementation
Albendazole supplementation
Data Collection
Before the actual data collection, the questionnaire (Annex A) will be pre-tested first in another city outside of Parañaque. Revisions of the questions will be made according to the results of the data collection.
Recruitment of cases
Subjects will be randomly selected from the masterlist of children aged 2 to 6 years per barangay in Paranaque City => Weighing and routine fecalysis will be done on each subject selected => if the result of the fecalysis is positive for at least 2 slides as reviewed by 3 medical technologist, the trained interviewer will check eligibility of patient as a case => if the subject meets the eligibility criteria, the interviewer will do the face to face interview with the mother ( in the absence of a mother, subject's father can be the informant) and fills in the questionnaire=>after completion of a batch of five cases and 5 controls, questionnaires will be submitted to his/her supervisor for review of questionnaires.
Recruitment of controls
Subjects will be randomly selected from the masterlist of children aged 2 to 6 per barangay => Routine fecalysis will be done on each subject selected => if the result of the fecalysis is negative for at least 2 slides as reviewed by 3 medical technologist, the trained interviewer will check eligibility of patient as a control => if the subject meets the eligibility criteria, the interviewer will do the face to face interview with the mother ( in the absence of a mother, subject's father can be the informant) and fills in the questionnaire=>after completion of a batch of five cases and 5 controls, questionnaires will be submitted to his/her supervisor for review of questionnaires.
Data Processing
a. Data Quality and Data Quality Control
A training of the interviewers will be done before the actual interviews. An interview manual designed for this study will be devised to facilitate the training. The interviewers will ensure that each question is completely answered and must check for consistency of the answers prior to proceeding to the next question.
All questionnaires that have been accomplished will be inspected by the field supervisor. Completeness of the data as well as inconsistencies will be checked while the interviewers are still on field. Data will be encoded by two encoders and will be compared to eliminate error in encoding. Any inconsistencies will be double checked for accuracy. Contact numbers of the respondents will be requested to allow follow up in the future.
b. Data organization
Data will be encoded and processed using EpiInfo 6. Statistical analyses will be done using the same software.
Limitations of the Study
Information bias may occur when the respondent is not the direct caregiver of the child. Also, recall bias may occur when the respondent cannot recall if the child has or has not taken vitamin A supplementation. Specifically, misclassification bias in terms of ascertainment of exposure may occur when the study population, both cases and control, may not have information on exposure. However, this may be addressed by follow up of the respondents when another person in their household is more knowledgeable about vitamin A supplementation.
Another potential limitation of the study is the challenge in the inclusion of children from the exclusive subdivisions/homes in Parañaque which could not be controlled. This might overestimate the results of the study and can cause a positive bias directed away from the null. Coordination with the homeowner's association may be done to request permission to conduct the study in the exclusive subdivisions. This can be controlled in the analysis stage through multiple linear regressions.
Ethical Considerations
All respondents will be given an informed consent form taking into consideration their cultural, religious and gender principles. The consent form will include the following information:
title and a brief description of the study;
date when the form was prepared or revised;
that the individual is being invited to participate in the research as well as the reason for the invitation;
objectives and the methods of the research;
expected duration of their participation;
a description of the potential benefits of the outcome of the research to the participants or to others;
the extent to which the confidentiality of records will be and can be maintained; and
that the respondent is free to refuse to participate and to withdraw from the research anytime without penalty or loss of benefits that he or she is otherwise entitled.
In order for the research to avoid potential harm to the subjects, the following rights will strongly be observed at the time of the study:
The respondent has the right not to join the study.
The respondent has the right not to answer all the questions that the interviewer will ask.
The respondent has the right to know the purpose of the study.
The respondent has the right to confidentiality of his/her identity.
The respondent has the right to terminate his/her participation during the time of research.
The respondent has the right to know the result of the research he/she participated.
Moreover, in order for the respondents to confidently answer the interviewer, an assurance of confidentiality or anonymity of his/her identity will be assured. This research will not only consider the quality of data to be collected but also the rights of every individual whether respondents or interviewers right. A token of appreciation will also be given to those respondents who shared their time for the success of the study.
