The risk factors for hookworm infection are multi-factorial and they operate on different levels. Typical analyses of hookworm infection disparities have focused largely on either individual- or ecologic-level determinants, and none has analyzed them on both levels simultaneously. Hence, this study aimed to fill the need of simultaneously analyzing the correlates of hookworm infection on different levels, using the multilevel model.
The general objective of the study was to identify the individual-level, barangay-level and provincial-level factors associated with hookworm infection in selected provinces in Mindanao. This thesis was a cross-sectional study that uses several secondary datasets. Individual-level variables were age, gender and hookworm infection status. The level 2 variables were land cover type (or also known as vegetation), barangay income classification, literacy rate and percentage of households without any form of toilet facility. The level 3 variables were climate type, average monthly rainfall and average monthly maximum temperature. The Mindanao provinces that were included in the study were Agusan del Sur, Davao del Sur, South Cotabato, Surigao del Sur, Misamis Oriental, Bukidnon, Surigao del Norte.
Descriptive and crude analyses of hookworm infection were done using Microsoft Excel 2007 and Stata 10. Multilevel modeling was done using the Generalized Linear Latent and Mixed Models (GLLAMM) in Stata. The significant correlates of hookworm infection at the individual level are older age and male gender. While at the barangay level, it is a predominantly cultivated land cover. At the provincial level, these are average rainfall ≥100mm during LAR, average rainfall ≤100mm during HAR and Type 3 climate (seasons are not very pronounced). The significant factors at the barangay and provincial level can be used as criteria for selecting target areas for specific STH interventions. The STH interventions, which is primarily deworming, could expand its coverage and include as beneficiaries the older individuals.
Table of Contents
CHAPTER I INTRODUCTION
1.1 Background of the Study
1.2 Statement of the Problem
1.3 Objectives of the Study
1.4 Significance of the Study
CHAPTER II THEORETICAL BACKGROUND
2.1 Review of Related Literature
2.1.1 Etiology and Pathophysiology of Hookworm Infection
2.1.2 Health Impact of Hookworm Infection
2.1.3 Determinants of Hookworm Infection
2.1.4 Multilevel Analysis
2.2 Conceptual Framework
CHPATER III METHODOLOGY
3.1 Research Design
3.2 Sources of Data
3.2.1 Prevalence Survey for Schistosomiasis
3.2.2 The Group-Level Datasets
3.3 Study Areas and Number of Respondents
3.4 Definition of Variables
3.5 Data Processing
3.6 Data Analysis
3.6.1 Descriptive Analysis
3.6.2 Inferential Analysis
CHAPTER IV RESULTS OF THE STUDY
4.1 Descriptive Analysis
4.1.1 First-level Variables
4.1.2 Second-level Variables
4.1.3 Third-level Variables
4.1.4 Hookworm Prevalence
4.2 Inferential Analysis
4.2.1 Crude Association of Hookworm Infection With Individual-Level Variables
4.2.2 Crude Association of Hookworm Infection With Barangay-Level Variables
4.2.3 Crude Association of Hookworm Infection with Provincial-Level Variables
4.2.4 Multilevel Modeling
CHAPTER V DISCUSSION OF RESULTS
5.1 Analytic Techniques
5.1.1 Barangay-level variability of risk for hookworm infection
5.2 Correlates of hookworm infection
5.2.1 Individual-level correlates
5.2.2 Barangay-level correlates
5.2.3 Provincial-level correlates
5.3 Validity
5.3.1 Selection Bias
5.3.2 Information Bias
5.3.3 Confounding
CHAPTER VI CONCLUSIONS AND RECOMMENDATIONS
6.1 Summary
6.2 Conclusions
6.3 Recommendations
Research Objectives and Thematic Focus
This study aims to simultaneously analyze the factors associated with hookworm infection across three distinct levels—individual, barangay, and provincial—using a multilevel model to provide a comprehensive understanding of disease causation in Mindanao, Philippines.
- Identification of individual-level risk factors (age and gender).
- Assessment of barangay-level socioeconomic and environmental determinants.
- Evaluation of provincial-level climatic variables and their impact on hookworm survival.
- Investigation of cross-level interactions between environmental characteristics and infection risk.
- Application of multilevel modeling to account for hierarchical data structures and clustering effects.
Excerpt from the Book
2.1.1 Etiology and Pathophysiology of Hookworm Infection
The most common hookworms that infect man are N. americanus and A. duodenale. They are blood-sucking nematodes that attach to the mucosa of the small intestine and occur as single or mixed infections with other soil-transmitted helminths.
Hookworm eggs exit the human body in feces and, when deposited in moist and shaded soil with adequate warmth of around 25–35oC, hatch into first stage larvae within 24 to 48 hours. Development to first-stage larvae is slower at more extreme temperatures (Pawlowski et al., 1991); in fact, at 15oC hatching does not occur until the fifth day and development of larvae slows down as temperature increases up to 40oC. Some 90% of A. duodenale and N. americanus eggs hatch at temperatures that range from 15-35oC and 20-35oC, respectively. A. duodenale fails to hatch above 40oC; N. americanus above 45oC (Pawlowski et al., 1991).
Hookworm larvae molt twice as they develop to third-stage non-feeding organisms. At this stage, the larva can live for several weeks in the soil until their lipid metabolic resources are exhausted (Hotez et al., 2004). The third-stage larvae are very active. They can move upwards to the uppermost layer of the soil as long as it is moist enough (Pawlowski et al., 1991).
The natural history of hookworm infection may involve (1) the skin at the site of entry of the filariform larvae and as for the species A. duodenale, it may be also acquired through oral route (WHO, 1964); (2) the lung during larval migration; and, (3) the small intestines which is the habitat of the adult worms.
Summary of Chapters
CHAPTER I INTRODUCTION: This chapter establishes the public health significance of hookworm infection and outlines the study's goal to investigate its determinants across multiple hierarchical levels.
CHAPTER II THEORETICAL BACKGROUND: This section reviews existing literature on hookworm etiology, impact, and the theoretical framework of multilevel analysis.
CHPATER III METHODOLOGY: This chapter details the cross-sectional research design, the hierarchical data structure, and the statistical methods used, including multilevel logistic regression.
CHAPTER IV RESULTS OF THE STUDY: This chapter presents the descriptive statistics and the results of the crude and multilevel analyses concerning individual, barangay, and provincial correlates.
CHAPTER V DISCUSSION OF RESULTS: This section interprets the findings, addresses the validity of the results regarding bias and confounding, and compares the study outcomes with existing scientific literature.
CHAPTER VI CONCLUSIONS AND RECOMMENDATIONS: The final chapter summarizes the significant risk factors identified and provides policy recommendations for soil-transmitted helminthiasis control programs.
Keywords
Hookworm infection, Multilevel analysis, Epidemiology, Mindanao, Philippines, Soil-transmitted helminths, Public health, Risk factors, Environmental determinants, Logistic regression, Iron deficiency anemia, Parasitology, Hierarchical modeling, Disease control.
Frequently Asked Questions
What is the primary focus of this research?
The research focuses on identifying the multi-factorial risk factors for hookworm infection across individual, barangay, and provincial levels in selected provinces of Mindanao, Philippines.
Why is a multilevel analysis approach used here?
It is used because the data has a hierarchical structure (individuals nested within barangays, which are nested within provinces), and traditional regression models fail to account for this clustering, which could lead to invalid statistical inferences.
What are the main findings regarding individual-level factors?
The study found that being older (15 years and above) and being male are significant individual-level correlates for higher hookworm infection prevalence.
How does environment affect hookworm transmission?
Environmental factors such as predominantly cultivated land at the barangay level and specific rainfall patterns and climate types at the provincial level significantly influence hookworm survival and transmission.
What is the significance of the study's results for policy?
The identified significant risk factors at the barangay and provincial levels can guide the Department of Health (DOH) in geographically targeting deworming interventions and expanding coverage to include older, economically productive populations.
Which statistical tools were utilized for the analysis?
The study used Microsoft Excel 2007 and Stata 10, specifically employing the Generalized Linear Latent and Mixed Models (GLLAMM) to conduct multilevel modeling.
What role does land cover play in the infection risk?
Cultivated land is associated with a significantly higher prevalence of hookworm infection, likely because it provides moist conditions and vegetation cover that protect larvae from ultraviolet radiation and heat.
How did the study address potential bias and confounding?
The researchers conducted a validity assessment, acknowledging potential selection and information bias while arguing that the use of a multilevel model helped control for mutual confounding effects between environmental variables.
- Citar trabajo
- Genevieve Nangit (Autor), 2017, Correlates of Hookworm Infection in Selected Provinces of Mindanao, Philippines. A Multilevel Analysis, Múnich, GRIN Verlag, https://www.grin.com/document/421618
