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INTRODUCTION Soil-transmitted helminths include roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura), and hookworm (Ancylostoma duodenale/Necator americanus). These intestinal parasites are responsible for many human health problems, causing malnutrition in children [17], [18]. Hookworm also causes anemia, micronutrient deficiency, and many other complications [16], [61]. In 2017, the World Health Organization reported that more than 1.5 billion people (25% of the world''s population) are infected with soil-transmitted helminths, mostly in tropical countries in Africa, America, China, and Western Asia [119]. Dak Lak is one of the Central Highlands provinces where people’s habits of living, eating and farming are outdated. Therefore, the prevalence of worm infection in the province is very high, especially in primary school children, which affects not only the physical development but the intellectual development of children, especially ethnic minority children, including Ede children. So, we conducted the study: Situation and some related factors to soil-transmitted helminth infection among Ede primary school children in Krong Pac district, Dak Lak province and effectiveness of intervention (2015-2016)”. The objectives of the study are: 1- To evaluate the situation and related factors to soil-transmitted helminth infection among Ede primary school chilren in 4 communes of Krong Pac district, Dak Lak province in 2015. 2- To identify the species composition of hookworm by morphology and molecular biology. 3- To evaluate the effectiveness of interventional treatment with albendazole in combination with education and communication (2015-2016). NOVELTY AND SCIENTIFIC SIGNIFICANCE OF THE THESIS 1. Novelty - The study presents a picture of soil-transmitted helminth infection in Ede primary school children in Krong Pac district, Dak Lak province. Results showed that they were mainly infected with hookworms. - The study employed the method of culture and species identification of hookworm by morphology and molecular biology and the hookworm was identified as Necator americanus. The results were published in a recognized international journal. 2. Scientific significance The thesis results revealed the prevalence, intensity of soil-transmitted helminth infection and some related factors including: no use of latrines at home, at school; open defecation; no washing hands with soap after defecation; going barefoot to the field and at home; unhygienic latrines; and poor knowledge of parents about helminths and their effects. The average Hb and Hct of the infected students were lower than that of the uninfected ones. The thesis also determined the role of communication and education in the prevention of soil-transmitted helminthiasis in primary school children.
1 INTRODUCTION Soil-transmitted helminths include roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura), and hookworm (Ancylostoma duodenale/Necator americanus) These intestinal parasites are responsible for many human health problems, causing malnutrition in children [17], [18] Hookworm also causes anemia, micronutrient deficiency, and many other complications [16], [61] In 2017, the World Health Organization reported that more than 1.5 billion people (25% of the world's population) are infected with soil-transmitted helminths, mostly in tropical countries in Africa, America, China, and Western Asia [119] Dak Lak is one of the Central Highlands provinces where people’s habits of living, eating and farming are outdated Therefore, the prevalence of worm infection in the province is very high, especially in primary school children, which affects not only the physical development but the intellectual development of children, especially ethnic minority children, including Ede children So, we conducted the study: Situation and some related factors to soil-transmitted helminth infection among Ede primary school children in Krong Pac district, Dak Lak province and effectiveness of intervention (2015-2016)” The objectives of the study are: 1- To evaluate the situation and related factors to soil-transmitted helminth infection among Ede primary school chilren in communes of Krong Pac district, Dak Lak province in 2015 2- To identify the species composition of hookworm by morphology and molecular biology 3- To evaluate the effectiveness of interventional treatment with albendazole in combination with education and communication (2015-2016) NOVELTY AND SCIENTIFIC SIGNIFICANCE OF THE THESIS Novelty - The study presents a picture of soil-transmitted helminth infection in Ede primary school children in Krong Pac district, Dak Lak province Results showed that they were mainly infected with hookworms - The study employed the method of culture and species identification of hookworm by morphology and molecular biology and the hookworm was identified as Necator americanus The results were published in a recognized international journal Scientific significance The thesis results revealed the prevalence, intensity of soiltransmitted helminth infection and some related factors including: no use of latrines at home, at school; open defecation; no washing hands with soap after defecation; going barefoot to the field and at home; unhygienic latrines; and poor knowledge of parents about helminths and their effects The average Hb and Hct of the infected students were lower than that of the uninfected ones The thesis also determined the role of communication and education in the prevention of soil-transmitted helminthiasis in primary school children THESIS STRUCTURE The thesis consists of 126 pages (excluding references and appendices) divided into the following sections: Introduction (2 pages), literature review (33 pages), study subjects and methods (25 pages), results (30 pages), discussions (32 pages), conclusions (2 pages), and recommendations (1 page) There are 120 references including 85 Vietnamese references and 35 English references, 31 tables, 16 figures, and appendices Chapter 1: LITERATURE REVIEW 1.1 An overview of studies on soil-transmitted helminthiasis Roundworm, whipworm, and hookworm have plagued humans since before the era of our earliest recorded history The diseases they cause are reported in ancient medical literature In Vietnam, the documents on helminthiases as well as remedies to cure them were mentioned in the 14th century In the late nineteenth century and early twentieth century, scientists conducted the first surveys on helminthiases, i.e Séguin (1905), Mouzels (1907), Mathis and Léger (1911), etc Since 1954, especially after the unification of the country, there have been thousands of studies conducted on many aspects of helminthiasis, including soil-transmitted helminth infection such as studies on epidemiology, pathology, immunology, diagnosis, treatment and prevention 1.2 Biological characteristics of soil-transmitted helminths (STH) 1.2.1 Life-cycle Life-cycle of soil-transmitted helminths is simply the process when an individual is infected with eggs or larvae, then eggs or larvae develop into adult worms, which produce eggs The eggs are passed in the faeces Human Environment 1.3 The situation of STH infection 1.3.1 The situation of STH infection in the world 1.3.1.1 STH infection in the community WHO reports that Ascaridosis (roundworm infection) is the most common disease and widespread in many countries over the world An estimated 25% of the world’s population are infected with STH infections worldwide Infections are widely distributed in tropical and subtropical areas In 1995, WHO reported 1.5 billion people infected with hookworm and 65,000 people died from hookworm each year 1.3.1.2 STH infection in school children STH infection such as roundworm, whipworm, and hookworm is very common in school-age children with the highest prevalence and intensity in tropical and subtropical areas A high prevalence of STH infection among school-age children has been reported in many countries such as Panama, China, USA, Mexico, and Colombia They realise that the prevalence (70 - 95%) is the highest in children aged to years old, then decreases by age and reaches the lowest level of 10 - 50% in adults WHO, 2017 revealed that over 600 million school-age children live in areas where these parasites are intensively transmitted, and are in need of treatment and preventive interventions 1.3.2 STH infection in Vietnam 1.3.2.1 STH infection in the community According to inadequate data collected from provinces all over the country, there are an estimated 60 million roundworm infections, 40 million whipworm infections and 20 million hookworm infections The prevalence of roundworm infection in the North is the highest: 8095% in the Northern Delta, 80-90% in the midlands, 50-70% in the mountainous areas, and 70% in the coastal areas In the Central of Vietnam, the prevalence is lower: 70.5% in the delta, 38.4% in the mountainous area, and 12.5% in the coastal area In the South, the prevalence is 45-60% in the delta, below 10% in the Cuu Long delta, and 10-25% in the Highlands Whipworm is distributed as follows: In the north: 58-89% in the delta, 38-41% in the midland, 29- 52% in the mountainous area, and 28-75% in the coastal area; in the Central: 27-47% in the delta, 4.2 - 10.6% in the mountains, 12.7% in the coast; in the South: 0.5-1.5% in the delta, 1.7% in the Central Highlands Similarly, the prevalence of hookworm infection is: in the North: 30-60% in the delta, 64% in the midland, 61-85% in the mountains, 67% in the coast; in the Central: 52% in the delta, 61% in the mountains, 68% in the coast; in the South: 52% in the delta, and 47% in the Central Highlands 1.3.2.2 The situation of STH infections in primary school children In Vietnam, many studies on STH infections among primary school children have been conducted with very different prevalences in different regions According to the study on the situation of intestinal helminthiasis among primary school children in some provinces of Vietnam by Nguyen Thu Huong et al (2012), the prevalance of worm infection was still 16.3% (ranging from 1.8 to 34.8%) after 10 years of deworming 1.3.2.3 The situation of STH infections in Dak Lak STH infection is common in low-income communities, including Dak Lak The prevalence of STH infection in Dak Lak in 1996 was 88.97%; in 2002 71.87%; in 2007 46.32%; and 2010 75.1% 1.4 Impacts of STH infections Soil-transmitted helminthiases affect people of all ages silently and in a long-term They take nutrients, reduce the human body's ability to work, and cause memory loss In children, STH infection results in malnutrition, anemia, and mental retardation 1.5 Related factors to STH infections Roundworm, whipworm, and hookworm are human intestinal parasites They are only infectious when eggs develop into larvae Therefore, factors affecting the survival and development of their eggs as well as external factors (temperature, humidity, oxygen, light , pH of soil ) have an important influence 1.6 Diagnosis and treatment of STH infections Ascariasis (the disease caused by roundworm) and Trichuriasis (the disease caused by whipworm) have no specific clinical signs Anemia is a manifestation of hookworm disease in the late stage, especially severe infection can cause a change to specific skin color (yellow gold ), edema and signs of heart, liver, or kidney failure The diagnosis of STH infection is mainly based on faecal examination for eggs, which is a simple and accurate method - Currently, roundworm and hookworm are treated with Albendazole, Mebendazole and Pyrantel-pamoat And Albendazol and Mebendazol are used for treatment of whipworm - Deworming for primary schools from 2000 but up to now, the helminthic infection is so high Chapter 2: STUDY SUBJECTS AND METHODS 2.1 Subjects and location of the study - For evaluation of STH infections and anemia: + Ede primary school children (aged 6-12 years old) in Krong Pac district, Dak Lak province: Ly Thuong Kiet primary school, Krong Buk commune: 300 Ede students Ngo Gia Tu primary school, Tan Tien commune: 309 Ede students Ly Tu Trong primary school, Ea Uy commune: 316 Ede students No Trang Long primary school, Ea Yong commune: 354 Ede students - For intervention: Two schools with a similar prevalence were chosen for intervention Ly Thuong Kiet is the control school and Ly Tu Trong is the intervention school A total of 100 students with the highest intensity of hookworm infection were selected for stool sampling (about 10g) for larval culture 2.2 Study duration From January 2015 to December 2016 2.3 Study methods 2.3.1 Study design: - A descriptive cross sectional method (for objectives and 2) - A controlled community intervention (for objective 3) 2.3.2 Sample size and sampling 2.3.2.1 Sample size for studying worm infection and anemia: We use this formula for calculating the sample size: where n is the required sample size p = Expected prevalence z1-α/2 = confidence coefficient; at a confidence level of 95%, z1-α/2 is 1.96 d = Absolute error, we decided d = 5% (0.05) Based on the study by Than Trong Quang in 2009 that the prevalence of intestinal helminthiasis among children in Dak Lak province was 75.1%, we decided p = 75% (= 0.75) Our theoretical calculation produced n = 288 Since the number of Ede pupils in schools was 300, 309, 316 and 354 pupils respectively, we enrolled them all 2.3.2.2 Sample size for intervention: We use the formula: n= ( Ζ1−α / + Ζ1−β ) [ P1 (1 − P1 ) + P2 (1 − P2 )] ( P1 − P2 ) - Where: + P1: The expected prevalence of worm infections through the first stage of the study which was 75% (0.75) + P2 The expected prevalence after intervention which was 45% = 0.45 (decreased 30% in comparison with before intervention) + α: The significance level which was defined as 0.05 => Z1-α/2 = 1.96 + β: It is 0.10 => Z1-β = 1.28 Putting this into the formula we have a theoretical sample size n = 73.06 We took 75 pupils in each intervention school Therefore we had 150 pupils for intervention in total 2.4 Techniques used for information collection 2.4.1 KAP survey 2.4.2 Kato-Katz technique 2.4.3 Harada Mori Culture 2.4.4 Molecular biology (PCR with ITS1) 2.4.5 Blood test for hemoglobin (Hb) and hematocrit (Hct) Hb and Hct were measured using HemoCue 2.4.6 Data processing methods - The data collected in the study were processed using biostatistical method and SPSS 11.5 software - Bioinformatics tools were applied for molecular biology data 2.5 Research ethics The students were informed in advance and explained the purpose, requirement and benefit of the study They were voluntarily invovled in the study They could withdraw their particiaption from the study without any form of reprimands Those students who refused to cooperate would be excluded from the study Chapter 3: STUDY RESULTS 3.1 Situation and some related factors to soiltransmitted helminth (STH) infection among Ede primary school children in study schools 3.1.1 STH infection among the pupils Table 3.1 Sex distribution Males Females Total School Number Percentage Number Percentage number % % LTK (1) 152 51.0 146 49.0 298 LTT (2) 174 55.1 142 44.9 316 NGT (3) 157 52.2 144 47.8 301 NTL (4) 152 52.2 139 47.8 291 Total 635 52.7 571 47.4 1206 p1,2,3,4 > 0.05 > 0.05 > 0.05 Notes: LTK: Ly Thuong Kiet primary school; LTT: Ly Tu Trong primary school; NGT: Ngo Gia Tu primary school; NTL: No Trang Long primary school Comments: The total number of pupils in study schools was 1206, distributed evenly among the schools The difference in gender was not statistically significant Table 3.2 Prevalence of STH infection in the pupils Number Roundworm Whipworm Hookworm School of (+) % (+) % (+) % samples LTK (1) 298 2.4 0.3 89 29.9 LTT (2) 316 10 3.2 0.3 103 32.6 NGT (3) 301 0.7 0.3 52 17.3 NTL (4) 291 1.7 0.3 31 10.7 Total 1206 24 2.0 0.3 275 22.8 P p(1,2) – (3,4) < 0.05 Comments: Stool examination by Kato-Katz technique for 1206 students showed that the overall prevalence of soil-transmitted helminth infection was 25.0% (12.7 - 35.8%) 10 Table 3.3 Intensity of infection Roundworm Whipworm Hookworm Posit Posi Positi ive EPG tive EPG EPG ve (+) (+) (+) 1,2 ± 2,4 0,2 89 75,2 ± 5,7 School LTK (1) LTT (2) 10 3,7 ± 4,4 0,2 103 85,4 ± 6,8 NGT (3) 0,2± 0,1 0,1 52 22,5 ± 4,9 NTL (4) 3,0 ± 2,6 0,2 31 13,0 ± 3,1 Total 24 2,0 ± 1,5 0,1 275 49,7 ± 8,5 p(1,2) – (3,4) < 0.05 p < 0.05 > 0.05 p1-2 > 0.05; p3-4 > 0.05 Comments: The infection intensity for all schools was mild (85.4 eggs per gram of feces 0.05 Comments: Of the surveyed schools, three schools showed an association between anemia and worm infection with p