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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)
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 THIS THESIS IS ACCOMPLISHED AT THE NATIONAL INSTITUTE OF HYGIENE AND EPIDEMIOLOGY Scientific supervisors: Assoc.Prof Nguyen Van Chuong, Ph.D 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: National Library of Viet Nam Library of the National Institute of Hygiene and Epidemiology 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 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 (20162017) 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 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: - 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% 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, socioeconomic 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 METHODOLOGY 2.1 Study objects - The sampling frame is applied to select a person aged from 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 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 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) 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 to 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 - 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 n z / 2 p 1 p z p1 1 p1 p2 1 p2 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 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 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 No No p Commune Gender examined % infected Male 318 53 16.7 Duc >0.05 Phong Female 344 66 19.2 Duc Chanh Total Male 323 45 13.9 Female 342 66 19.3 Male 641 98 15.3 Female 686 132 19.2 >0.05 >0.05 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 > 15 435 90 20.7 Duc 15 415 79 19.0 15 850 169 19.9 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) Infected (%) Table 3.24 Association between living habits and Toxocara infections Not Total Infected OR p infected (%) (CI 95%) (%) 24 24 48 Yes Regularly (50.0) (50.0) 4.9 < 0.01 carrying (2.5-9.7) 59 293 352 dogs No (16.8) (83.2) 63 167 230 Yes Regularly (27.4) (72.6) 2.8 playing with < 0.01 (2-7.0) 20 150 170 soil No (11.8) (88.2) 38 77 115 HandYes 2.6 (33.0) (67.0) washing after (1.6-4.5) < 0.01 contacting 45 240 285 No soil (15.8) (84.2) 22 65 87 Regularly Yes (25.3) (74.7) washing 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 0.05 Interven tion effect % p 2&4 32.7 < 0.01 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 ntion commu ne Contro l commu ne Before intervention (1) After intervention (2) Before intervention (3) After intervention (4) 662 61 9.2 42.4 627 33 5.3 < 0.01 665 59 8.9 7.9 632 52 8.2 > 0.05 34.5 < 0.05 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 Control 61 (100.0) (8.2) 59 11 91.8 81.4 (100.0) (18.6) Total 120 16 (%) 61 (100.0) (4.9) 59 95.1 86.4 (100.0) (13.6) 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 ed p % ed p 2&4 80.9 Interve Before 126 42 33.0 n tion intervention (1) 0.05 66.6 c intervention (2) > 0.05 playg Contr Before 10 20.0 round ol intervention (3) After 10 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 Interve ntion commu ne Contro l commu ne Before intervention (1) After intervention (2) Before intervention (3) After intervention (4) No examin ed No infect ed % 200 14 7.0 200 2.0 200 13 6.5 200 13 6.5 Effectiv e index % p Interven tion effect % p 2&4 71.4 < 0.05 71.4 0.05 The proportions of vegetable samples contaminated with Toxocara eggs in the intervention commune reduced from 7.0% to 2.0% (p 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 23.4 < 0.01 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 After (4) 102 51.0 (n=200) In the intervention commune, significant increase was found in the practice on toxocariasis control activities (from 41.5% to 67.0%, p 0.05 After (4) Before (1) 112 141 56.0 70.5 After (2) Before (3) 171 144 85.5 72.0 After (4) Before (1) 154 160 77.0 80.0 After (2) Before (3) 177 88.5 10.6 < 0.05 153 76.5 4.6 After (4) 160 80.0 > 0.05 4.8 > 0.05 < 0.01 31.6 < 0.01 25.6 < 0.01 6.0 > 0.05 In the intervention commune, significant reduction was found in the practice of carrying dogs (p 0.05 21.3 < 0.01 6.9 > 0.05 Interventi on effect % p 2&4 8.7 > 0.05 14.4 < 0.05 6.0 < 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