Tóm tắt Luận án Situation and associated factors of toxocara canis infection in Mo duc district, Quang ngai province in 2016, and effectiveenss of intervention measures

Toxocariasis is a zoonotic disease, which is transmitted to humans from swallowing larvae of the two species Toxocara canis and Toxocara cati. The larvae can parasite on bodily organs such as brain, eyes, liver, and lungs ; and can cause serious symptoms such as epilepsy, vision impairment or even blindness. Toxocariais is distributed from Southern hemisphere to tropical countries, with different prevalence, from 0.7% in New Zealand to 93.0% in La Reunion (Africa). In Viet Nam, the increase in the infection of the disease in recent years has caused negative impact on the health of the community. However, little has been known of the studies on the current situation of toxocariasis, as well as the associated factors of the disease. In addition, no appropriate control measures have been in place to be applied in to the community level. This study was conducted as a contribution to seek for the understanding of the distribution and associated factors of toxocariasis, and to propose timely and appropriate intervention measures, so as to help reduce the incidence in the community

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1 MINISTRY OF EDUCATION AND TRAINING MINISTRY OF HEALTH NATIONAL INSTITUTE OF HYGIENE AND EPIDEMIOLOGY --------- BUI VAN TUAN SITUATION AND ASSOCIATED FACTORS OF TOXOCARA CANIS INFECTION IN MO DUC DISTRICT, QUANG NGAI PROVINCE IN 2016, AND EFFECTIVEENSS OF INTERVENTION MEASURES Major: Public Health Major code: 62 72 03 01 SUMMARY OF THE THESIS FOR THE DEGREE OF DOCTOR OF PUBLIC HEALTH Ha Noi - 2018 2 THIS THESIS IS ACCOMPLISHED AT THE NATIONAL INSTITUTE OF HYGIENE AND EPIDEMIOLOGY Scientific supervisors: 1. Assoc.Prof. Nguyen Van Chuong, Ph.D. 2. Prof. Vu Sinh Nam, Ph.D. Examiner 1: .............................................................................................................................................. .............................................................................................................................................. Examiner 2: .............................................................................................................................................. .............................................................................................................................................. Examiner 3: .............................................................................................................................................. .............................................................................................................................................. The thesis will be defended at the Board of Examiners of Institute at the National Institute of Hygiene and Epidemiology, at .. ., on .. ....., 2018. More information of the thesis will be retrieved at: 1. National Library of Viet Nam 2. Library of the National Institute of Hygiene and Epidemiology 3 INTRODUCTION Toxocariasis is a zoonotic disease, which is transmitted to humans from swallowing larvae of the two species Toxocara canis and Toxocara cati. The larvae can parasite on bodily organs such as brain, eyes, liver, and lungs ; and can cause serious symptoms such as epilepsy, vision impairment or even blindness. Toxocariais is distributed from Southern hemisphere to tropical countries, with different prevalence, from 0.7% in New Zealand to 93.0% in La Reunion (Africa). In Viet Nam, the increase in the infection of the disease in recent years has caused negative impact on the health of the community. However, little has been known of the studies on the current situation of toxocariasis, as well as the associated factors of the disease. In addition, no appropriate control measures have been in place to be applied in to the community level. This study was conducted as a contribution to seek for the understanding of the distribution and associated factors of toxocariasis, and to propose timely and appropriate intervention measures, so as to help reduce the incidence in the community. Objectives 1. To describe the current situation and associated factors of Toxocara canis on humans in Mo Duc district, Quang Ngai province in 2016. 2. To evaluate the effectiveness of some intervention measures applied to control human toxocariasis at studied sites (2016- 2017). 4 New scientific ideas and significance of the study The thesis seeks to provide a systematic research on the situation and associated factors of human Toxocara canis infections in Mo Duc district, Quang Ngai province in 2016, and to evaluate effectiveness of intervention measures applied to the community. This is the first study ever conducted in Viet Nam in terms of introducing intervention measures to human toxocariasis control, which indicates that the combined health education and deworming for dogs are effective measures to reduce the infections in the community and to improve the knowledge, attitude and practice of the high-risk population. The study is proven to be highly applicable, facilitating health care facilities at all levels to plan and implement control activities of toxocariasis in the community. THESIS SRUCTURE The thesis is composed of 117 pages (without references and appendices), which are divided into the Introduction (21 pages), background (34 pages), study objects and methodology (21 pages), study results (30 pages), discussions (27 pages), conclusions (2 pages), and recommendations (1 page). Chapter 1. BACKGROUND 1.1. Current situation of toxocariasis infection 1.1.1. Case definition of toxocariasis According to the “Case definition of infectious diseases”, as attachment to the Decision Number 4283/QĐ-BYT, dated August 8, 2016 by the minister of Health: 5 - A suspected case: A case is considered “suspected” upon having the following symptoms: prurigo, urticarial, headache, abdominal pain, dyspepsia; muscle pain, fatigue, fever, wheezing; involvement of the enlargement of the liver, pulmonia, chronic abdominal pain, neuropsychiatric symptoms, damage to the eye, vision impairment, endophthalmitis or papillitis, and distorted retina - A probable case: not applicable - A confirmed case: a suspected case with the presence of the toxocara larvae, or the detection of the antibody of the larvae with ELISA technique, or detection a specific gene portion of the larvae with molecular-biological technique. 1.1.2. Toxocara infections in the world Toxocariasis is present in all over the world, but in tropical countries, the disease is more prevalent. The disease is distributed from the southern hemisphere to Southern America, the Carriberian Sea, Africa, the Middle-East, South Asia and South-East Asia. In developed countries, toxocara infections vary, including New Zealand (0.7%), Japan (1.6%), Denmark (2.4%), Australia (7.5%), USA (14.0%), and Poland (15.0%). In tropical coutries, the disease accounts for high incidence, including Nigeria (30.0%), Swaziland (45.0%), Indonesia (63.2%), Malaysia (58.0%), and Braxin (36.0%). 1.1.3. Toxocara infections in Viet Nam Since 2000, there have been several studies conducted on the infections of toxocariasis in the community, which indicated different incidences depeding on the regions. In the North, the infections ranged from 58.7-74.9%, while in the South, the infections were from 38.4-53.58%. In Central Vietnam, some studies were carried out, with the average infection rates being from 13.1-50.0%. 6 1.2. Associated factors of toxocara infections Much have been studied to described the risk factors of toxocara infections. These include sources of transmission, outer settings (soil, vegetable garden) contaminated with Toxocara embryonated eggs, favourite climate and weather facilating the development and survival of eggs in the environment, socio- economic characteristics. In addition, human behaviours are considered risk factors such as free-ranged raising of dogs and cats, less frequent or no deworming of dogs and cats, carrying cats and dogs, eating raw vegetable, playing with soil, and no handwashing after playing with soil. 1.3. Control of toxocariasis All over the world, there ahve been a great deal of studies conducted on toxocariasis, but mainly focused on epidemiology, diagnosis, and treatment. However, less have been studied in the control of the disease, and just focussed on deworming for cats and dogs, management of pets, health education and introduction of laws on pet management. In Viet Nam, there have not any studies on toxocariasis control, since it is considered as one of the neglected tropical diseases. In recent years, increasing incidence of Toxocara infections has raised the necessity for the study of appropriate intervention measures for toxocariasis control, hence improving the health of the people. Chapter 2. METHODOLOGY 2.1. Study objects - The sampling frame is applied to select a person aged from 2 to 70 years old in each selected household. Domestic dogs, soil, and vegetable areas of the house were also selected. - Public soil areas and vegerables sold at the local markets were selected. 7 2.2. Duration of study: From April, 2016 to December, 2017. 2.3. Study sites The study was conducted at two villages: Van Ha village of Duc Phong commune and Village 4 of Duc Chanh commune, Mo Duc district, Quang Ngai province. 2.4. Study methods. 2.4.1. Descriptive cross-sectional design * Sample size: - The following formula was used to calculate the sample size for identifying the human toxocariasis incidence Z2(1/2).p.(1-p) n = ---------------- x DE (pƐ)2 Z1-α/2: Z value (at 1.96 for 95% confidence level) p: percentage of estimating the community incidence. In this study, p= 0.16 as referential proprotion by Bui Van Tuan in Bnih Dinh province. Ɛ: Effect size. In this study, Ɛ = 0,2. As this study involved two cluster samplings (first time at two villages, second time at household level), the DE was then calculated twice. With the design effect for each time at 1.5, so DE = 1.5 by 1.5 = 2.25, hence the sample size n = 1,147 people. An additional 10% was added to the sample, resulting in the total sample of 1,280 people for two villages, so there were 640 people from each village. In each household, there were estimated 3 to 4 people, so the total number of households in each village were 200. - Samlpe size for identifying the Toxocara infections in dogs:All dogs in 200 selected households - Sample size of soil: At households: 200 soil samples for each communes. At public playing places: 10 soil samples/commune 8 - Sample size of vegetable: 200 samples of vegetable at each study site. - Sample size for KAP survey: One person per household (200 household/commune). * Sampling technique: - Sampling for identifying the human toxocariasis incidence: 200 households per commune were selected by systematic ramdomization. - Sampling for KAP survey: householder (possible husband or wife of householder). - Sampling for identifying toxocara infection in dogs: dosmetic dogs in the selected household - Sampling for idetifying toxocara infection on vegetable: soil samples from 200 selected households. - Sampling of vegetable: Five kinds of vegetable most ofen eaten raw by people. 2.4.2. Community intervention design with control In this study, Duc Phong commune was selected as intervention commune and Duc Chanh as control commune. * Sample size for comparing the human Toxocara infections in two groups While: Z1-α/2: Z value (at 1.96 for 95% confidence level); Z1-β: = 0.84 when 1- = 80%; (, ) = 7.8; ∆ = p1 - p2 ; P = (p1 + p2)/2. p1: estimated infection rate at the control commune after intervention (p1=0.16). p2: estimated infection rate at the intervention commune after intervention (p2 = 0.11) Calculated samples: n1 = n2 = 577 people. An additional 10% was added to make up n1 = n2 = 635. Since the sample sizes for the intervention study was similar to those for cross-sectional study (n1 = n2 = 640), so the data from the cross-sectional study        2 / 2 1 1 2 2 2 2 1 1 1z p p z p p p p n         9 was used as the pre-intervention study. Similarly, data for the sample sizes for cross-sectional surveys on humans, dogs, soil, and vegetable were used as the pre-intervention study. * Intervention measures - Case treatment: The measure was applied to both intervention and control communes. - Health education, deworming for dogs: This measure was applied to the intervention commune. 2.5. Ethics in research - This study was conducted with the proposal being approved by the Board of bio-medical ethics, National Institute of Hygiene and Epidemiology. Chapter 3. RESULTS 3.1. Current situation and associated factors of human Toxocara infections 3.1.1. Human Toxocara seropositivity Table 3.3. Human Toxocara seropositivity at studied sites Commune Blood samples for ELISA No. infected % p Duc Phong 662 119 17.9 >0.05 Duc Chanh 665 111 16.7 Total 1,327 230 17.3 The overall seropositive rate of Toxocara canis was rather high in the two studied communes (17.3%), with the infection rates in Duc Phong and Duc Chanh communes being 17.9% and 16.7%, respectively. The infection rates in two communes were not significantly different. 10 Table 3.4. Toxocara infection by gender at study sites Commune Gender No. examined No. infected % p Duc Phong Male 318 53 16.7 >0.05 Female 344 66 19.2 Duc Chanh Male 323 45 13.9 >0.05 Female 342 66 19.3 Total Male 641 98 15.3 >0.05 Female 686 132 19.2 Toxocara seropositive rates in men and women were 15.3% and 19.2%, which were not significantly different. Table 3.5. Toxocara infection by age groups Commune Age groups No. examined No. infected % p Duc Phong > 15 435 90 20.7 <0.05 2 - 15 227 29 12.8 Duc Chanh > 15 415 79 19.0 <0.05 2 - 15 250 32 12.8 Total > 15 850 169 19.9 <0.01 2 - 15 477 61 12.8 Significant differences were found between Toxocara seropositive rates and age groups. 3.1.2. Human Toxocara infections Table 3.8. Human toxocara infections at studied sites Commune No. examined Seropositive (+) plus clinical symptoms % Duc Phong 662 61 9.2 Duc Chanh 665 59 8.9 Total 1,327 120 9.0 Overall human Toxocara infection rate at study sites was 9.0%. 11 3.1.3. Associated factors of Toxocara infections Table 3.11. Toxocara infections in dogs at studied sites Commune No. examined No. infected % p Duc Phong 126 42 33.3 >0.05 Duc Chanh 109 35 32.1 Total 235 77 32.8 The overall Toxocara infection in dogs at studied sites was 32.8%, with that at Duc Phong commune of 33.3%; and Duc Chanh of 32.1%. Table 3.13. Proportion of soil samples contaminated with Toxocara eggs Location of soil Commune No. examined No. contami nated % p At househol ds Duc Phong 200 59 29.5 >0.05 Duc Chanh 200 52 26.0 Total 400 111 27.8 At public placegro unds Duc Phong 10 3 30.0 >0.05 Duc Chanh 10 2 20.0 Total 20 5 25.0 The proportion of soil samples contaminated with Toxocara eggs was 27.8% at households and 25.0% at public playgrounds. 12 Table 3.15. Toxocara eggs contamination on vegetable Kinds of vegetable Duc Phong Duc Chanh Total No. examine d No. contaminat ed (%) No. examine d No. contaminat ed (%) No. examine d No. contaminat ed (%) mustard greens 40 2 (5.0) 40 1 (2.5) 80 3 (3.8) lettuce 40 5 (12.5) 40 4 (10.0) 80 9 (11.3) centella 40 1 (2.5) 40 2 (5.0) 80 3 (3.8) fish mint 40 3 (7.5) 40 4 (10.0) 80 7 (8.8) savory leaves 40 3 (7.5) 40 2 (5.0) 80 5 (6.3) Total 200 14 (7.0) 200 13 (6.5) 400 27 (6.8) The overall proportion of vegetable contaminated with Toxocara eggs was 6.8%; of which, the proportions of contaminated eggs was 11.3% on lettuce, 8.8% on fish mint, 6.3% on savory leaves, 3.8% on centella, and 3.8% on mustard green. Table 3.22. Association between dog raising and Toxocara infections Dog raising Infected (%) Not infected (%) Total OR (CI 95%) p Yes 49 (22.5) 169 (77.5) 218 1.2 (0.7-2.1) > 0.05 No 34 (18.7) 148 (81.3) 182 No significant association was found between Toxocara infection in people living in households with and without raising dogs (p>0.05). 13 Table 3.23. Association between eating vegetable and Toxocara infections Regularly eating vegetable Infected (%) Not infected (%) Total OR (CI 95%) p Yes 33 (22.1) 116 (77.9) 149 1.1 (0.6-1.9) > 0.05 No 50 (19.9) 201 (80.1) 251 No significant association was found between the regularlity of eating vegetable and Toxocara infections (p>0,05). Table 3.24. Association between living habits and Toxocara infections Living habits Infected (%) Not infected (%) Total OR (CI 95%) p Regularly carrying dogs Yes 24 (50.0) 24 (50.0) 48 4.9 (2.5-9.7) < 0.01 No 59 (16.8) 293 (83.2) 352 Regularly playing with soil Yes 63 (27.4) 167 (72.6) 230 2.8 (2-7.0) < 0.01 No 20 (11.8) 150 (88.2) 170 Hand- washing after contacting soil Yes 38 (33.0) 77 (67.0) 115 2.6 (1.6-4.5) < 0.01 No 45 (15.8) 240 (84.2) 285 Regularly washing hands before meals Yes 22 (25.3) 65 (74.7) 87 1.4 (0.8-1.9) > 0.05 No 61 (19.5) 252 (80.5) 313 Significant associations were found between regularly contacting soil, carrying dogs, and not washing hand after contacting soil and Toxocara infection (p<0.05). 14 3.2. Effectiveness of some intervention measures 3.2.1. Effectiveness of reducing seropositivity and infection rates of human toxocariasis 3.2.1.1. Changed seropositivity of human toxocariasis after intervention Table 3.25. Changed seropositivity of human toxocariasis Commune No. exam ined No. infect ed % Effective index % p Interven tion effect % p 2&4 Interve ntion commu ne Before intervention (1) 662 119 17.9 44.7 < 0.01 32.7 < 0.01 After intervention (2) 627 62 9.9 Contro l commu ne Before intervention (3) 665 111 16.7 12.0 > 0.05 After intervention (4) 632 93 14.7 After the intervention, the seropositivity reduced from 17.9% to 9.9% (p<0.01) at the intervention commune and reduced from 16.7% to 14.7% (p>0.05). The intervention effect was 32.7%. Table 3.26. Changed infection rates of toxocariasis after intervention Commune No. exa mine d No. infec ted % Effective index % p Interventi on effect % p 2&4 Interve ntion commu ne Before intervention (1) 662 61 9.2 42.4 < 0.01 34.5 < 0.05 After intervention (2) 627 33 5.3 Contro l commu ne Before intervention (3) 665 59 8.9 7.9 > 0.05 After intervention (4) 632 52 8.2 The infection rate of toxocariasis was reduced from 9.2% to 5.3% (p<0.01) at the intervention commune, and from 8.9% to 8.2% (p>0.05) at the control commune. The intervention effect was 34.5%. 15 3.2.1.2. Effectiveness of treatment with albendazol on Toxocariasis Table 3.27. Effectiveness of albedazol for the treatment of toxocariasis Commune Seropositivity (+) Confirmed cases Before (%) After (%) Effective index (%) Before (%) After (%) Effective index (%) Intervention 61 (100.0) 5 (8.2) 91.8 61 (100.0) 3 (4.9) 95.1 Control 59 (100.0) 11 (18.6) 81.4 59 (100.0) 8 (13.6) 86.4 Total 120 (100.0) 16 (13.3) 86.7 120 (100.0) 11 (9.2) 90.8 After one year, the seropositive and infection rates reduced by 86.7% and 90.8%, respectively. 3.2.2. Effectiveness of reducing the transmission sources in dogs and outer environment 3.2.2.1. Changed infection rates of Toxocara in dogs after intervention Table 3.30. Changed infection rates of Toxocara in dogs after intervention Examined dogs No. exa min ed No. infect ed % Effective index % p Interventi on effect % p 2&4 Interve n tion commu ne Before intervention (1) 126 42 33.0 80.9 <0.01 64.4 <0.01 After intervention (2) 111 7 6.3 Contro l commu ne Before intervention (3) 109 35 32.1 16.5 >0.05 After intervention (4) 97 26 26.8 The Toxocara infection rate in dogs at the interventi
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