Summary of the thesis for the degree of doctor of public health: Situation and associated factors of toxocara canis infection in mo duc district, quang ngai province in 2016, and effectiveenss of intervention measures

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To describe the current situation and associated factors of Toxocara canis on humans in Mo Duc district, Quang Ngai province in 2016. To evaluate the effectiveness of some intervention measures applied to control human toxocariasis at studied sites (2016- 2017)

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Nội dung Text: Summary of the thesis for the degree of doctor of public health: Situation and associated factors of toxocara canis infection in mo duc district, quang ngai province in 2016, and effectiveenss of intervention measures

1 MINISTRY OF EDUCATION MINISTRY OF AND TRAINING 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   2 z / 2 2 p 1  p   z p1 1  p1   p2 1  p2  n While: 2 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
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 Blood No. Commune samples for % p infected ELISA 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 examined No. No. % p infected Male 318 53 16.7 Duc >0.05 Phong Female 344 66 19.2 Duc Male 323 45 13.9 Chanh >0.05 Female 342 66 19.3 Male 641 98 15.3 >0.05 Total 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 Age No. No. Commune groups % p examined infected Duc > 15 435 90 20.7 15 415 79 19.0 15 850 169 19.9
11 3.1.3. Associated factors of Toxocara infections Table 3.11. Toxocara infections in dogs at studied sites No. No. p Commune % examined infected 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 No. Location No. Commune contami % p of soil examined nated Duc Phong 200 59 29.5 At >0.05 househol Duc Chanh 200 52 26.0 ds Total 400 111 27.8 Duc Phong 10 3 30.0 At public >0.05 placegro Duc Chanh 10 2 20.0 unds 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 Duc Phong Duc Chanh Total No. No. No. Kinds of No. No. No. contaminat contaminat contaminat vegetable examine examine examine ed ed ed d d d (%) (%) (%) mustard 2 1 3 40 40 80 greens (5.0) (2.5) (3.8) 5 4 9 lettuce 40 40 80 (12.5) (10.0) (11.3) 1 2 3 centella 40 40 80 (2.5) (5.0) (3.8) 3 4 7 fish mint 40 40 80 (7.5) (10.0) (8.8) savory 3 2 5 40 40 80 leaves (7.5) (5.0) (6.3) 14 13 27 Total 200 200 400 (7.0) (6.5) (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 Infected Not infected Total OR p Dog raising (%) (%) (CI 95%) 49 169 218 1.2 Yes (22.5) (77.5) 34 148 182 (0.7-2.1) > 0.05 No (18.7) (81.3) 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 Not Total Infected OR p eating infected (%) (CI 95%) vegetable (%) 33 116 149 Yes 1.1 (22.1) (77.9) > 0.05 (0.6-1.9) 50 201 251 No (19.9) (80.1) 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 Not Total Infected OR p Living habits infected (%) (CI 95%) (%) 24 24 48 Regularly Yes (50.0) (50.0) 4.9 < 0.01 carrying 59 293 352 (2.5-9.7) dogs No (16.8) (83.2) 63 167 230 Regularly Yes (27.4) (72.6) 2.8 playing with < 0.01 20 150 170 (2-7.0) soil No (11.8) (88.2) Hand- 38 77 115 Yes 2.6 washing after (33.0) (67.0) (1.6-4.5) < 0.01 contacting 45 240 285 No soil (15.8) (84.2) Regularly 22 65 87 Yes washing (25.3) (74.7) 1.4 > 0.05 hands before 61 252 313 (0.8-1.9) No meals (19.5) (80.5) Significant associations were found between regularly contacting soil, carrying dogs, and not washing hand after contacting soil and Toxocara infection (p
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. No. % Effective Interven exam infect index % tion ined ed p effect % p 2&4 Interve Before 662 119 17.9 44.7 ntion intervention (1) commu After 627 62 9.9 < 0.01 32.7 ne intervention (2) < 0.01 Contro Before 665 111 16.7 12.0 l intervention (3) commu After 632 93 14.7 > 0.05 ne intervention (4) After the intervention, the seropositivity reduced from 17.9% to 9.9% (p0.05). The intervention effect was 32.7%. Table 3.26. Changed infection rates of toxocariasis after intervention Commune No. No. % Effective Interventi exa infec index % on effect mine ted p % d p 2&4 Interve Before 662 61 9.2 42.4 ntion intervention (1) commu After 627 33 5.3 < 0.01 34.5 ne intervention (2) < 0.05 Contro Before 665 59 8.9 7.9 l intervention (3) commu After 632 52 8.2 > 0.05 ne intervention (4) The infection rate of toxocariasis was reduced from 9.2% to 5.3% (p0.05) 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 Before After Effective (%) (%) index (%) (%) index (%) (%) Intervention 61 5 91.8 61 3 95.1 (100.0) (8.2) (100.0) (4.9) Control 59 11 81.4 59 8 86.4 (100.0) (18.6) (100.0) (13.6) Total 120 16 86.7 120 11 90.8 (100.0) (13.3) (100.0) (9.2) 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. No. % Effective Interventi exa infect index % on effect min ed p % ed p 2&4 Interve Before 126 42 33.0 80.9 n tion intervention (1) commu After 111 7 6.3
16 Table 3.31. Chaged proportions of soil contaminated with Toxocara eggs Soil Commune No. No. % Effectiv Interven exami exami infe e index tion ned ned cted % effect % p p 2&4 Soil Interv Before 200 59 29.5 in entio intervention (1) 69.5 house n After 200 18 9.0 < 0.01 50.3 holds intervention (2) Contr Before 200 52 26.0 < 0.01 ol intervention (3) 19.2 After 200 42 21.0 > 0.05 intervention (4) Soil Interv Before 10 3 30.0 in entio intervention (1) 66.6 publi n After 10 1 10.0 > 0.05 66.6 c intervention (2) playg Contr Before 10 2 20.0 > 0.05 round ol intervention (3) 0 After 10 2 20.0 > 0.05 intervention (4) The proportion of soil contaminated with Toxocara eggs in households of the intervention commune reduced from 29.5% to 9.0% (p0.05). The intervention effect was 50.3%. The proportion of soild contaminated with Toxocara eggs in public playgrounds of the intervention commune reduced from 30.0% to 10.0%, while no change in this proportion was found in the control commune. Table 3.32. Chaged proportions of vegetable contaminated with Toxocara eggs Vegetable examined No. No. % Effectiv Interven examin infect e index tion ed ed % effect % p p 2&4 Interve Before 200 14 7.0 ntion intervention (1) 71.4 commu After 200 4 2.0 < 0.05 71.4 ne intervention (2) Contro Before 200 13 6.5 0.05 ne intervention (4) The proportions of vegetable samples contaminated with Toxocara eggs in the intervention commune reduced from 7.0% to 2.0% (p
17 3.2.3. Effectiveness of health education in improving the knowledge, attitude, and practice of the community on toxocariasis control 3.2.3.1. Changed knowledge of toxocariasis Table 3.33. Changed knowledge on risks of Toxocara infection Commune Correct % Effective Interventio answer index % n effect % p p 2&4 Intervention Before (1) 95 47,5 44,2 24,7 (n=200) After (2) 137 68,5 < 0,01 < 0,01 Control Before (3) 87 43,5 19,5 (n=200) After (4) 104 52,0 > 0,05 In the intervention commune, significant increase was found in the level of knowledge of the risks of infection (from 47.5% to 68.5%, p 0.05 In the intervention commune, significant increase was found in the level of knowledge of the risks of infection (from 48.5% to 69.0%, p 0.05 (n=200) In the intervention commune, significant increase was found in the practice on toxocariasis control activities (from 41.5% to 67.0%, p
18 Table 3.39. Changed practice on carrying dogs and treatment of dogs feces Practice Commune Yes % Effectiv Intervent e index ion effect % % p p 2&4 Regularly Intervention Before (1) 27 13.5 carrying (n=200) 66.7 dogs After (2) 9 4.5 < 0.01 61.9 Control Before (3) 21 10.5 (n=200) 4.8 < 0.01 After (4) 20 10.0 > 0.05 Treatment Intervention Before (1) 98 49.0 25.6 of dog (n=200) 31.6 feces After (2) 129 64.5 < 0.01 < 0.01 Control Before (3) 84 42.0 (n=200) After (4) 89 44.5 6.0 > 0.05 In the intervention commune, significant reduction was found in the practice of carrying dogs (p 0.05 8.7 After (2) 102 51.5 soil > 0.05 Control Before (3) 115 57.5 2.6 (n=200) > 0.05 After (4) 112 56.0 Washing Intervention Before (1) 141 70.5 21.3 hands (n=200) < 0.01 14.4 After (2) 171 85.5 after < 0.05 contacting Control Before (3) 144 72.0 6.9 (n=200) > 0.05 soil After (4) 154 77.0 Washing Intervention Before (1) 160 80.0 10.6 hands (n=200) < 0.05 6.0 After (2) 177 88.5 before < 0.05 meal Control Before (3) (n=200) 153 76.5 4.6 After (4) 160 80.0 > 0.05
19 In the intervention commune, significant reduction was found in the habits of washing hands after contacting soil (from 70.5 to 85.5%, p
20 4.1.2. Associated factors of Toxocara infections The overall proportion of Toxocara infection in dogs was 32.8%. This result was in agreement with other studies conducted in Nigeria from 2011-2012 with the infection rate of 34.6%; by Nguyen Van Chuong in Binh Dinh (22.8-32.4%) and in Dak Lak (35.8-37.0%); and by Bui Van Tuan in Binh Dinh and Gia Lai, with the infection rate of Toxocara canis in dogs being at 34.4-46.8%. The proportions of soil contaminated with Toxocara eggs in households and public playgrounds were 27.8% and 25.0%, respectively. These indicated high release of Toxocara larvae into the outer environment, especially soil settings. Our study result was harmonized with that conducted by Santarem (2008) in rural areas of the Sao Paolo state (Brazil), indicating the proportion of 29.03%. In addition, similar results were also fund in the studies conducted by Nguyen Van Chuong in Binh Dinh (20.0-25.0%); in Dak Lak (36.7-38.3%), by Bui Van Tuan in Binh Dinh and Gia Lai (26.8%), and by Tran Xuan Mai (from 5.0-26.0%), depending on typical geographical chacracteristics. The proportion of vegetable contaminated with Toxocara eggs was 6.8%. Kinds of vegetable often consumed are mustard greens, lettuce, centella, fish mint, and savory leaves, which all were contaminated with Toxocara eggs, with lettuce having the highest contamination rate (11.3%). Our study indicated similar result with the study conductd by Nguyen Van Chuong on vegetable in Binh Dinh (4.0-8.0%) and Dak Lak (1.0-3.0%). These kinds of vegetable are planted on ground, which are prone to dogs’ defecation. Our study also revealed the association between regularly carrying dogs, contacting soil, and not washing hands after contacting soil and Toxocara infection. The results were in line