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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 code: 62 72 03 01
Major: Public Health
SUMMARY OF THE THESIS FOR THE DEGREE OF DOCTOR OF PUBLIC HEALTH
Ha Noi - 2018
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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:
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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
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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).
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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:
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- A suspected case:
fatigue,
A case is considered “suspected” upon having the following symptoms: prurigo, urticarial, headache, abdominal pain, dyspepsia; muscle pain, 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%.
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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.
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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 soil each communes. At public playing places: 10 samples/commune
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- 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: for - Sampling the human identifying
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 ;
= (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
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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 % p No. infected Blood samples for ELISA
Duc Phong 662 119 17.9 >0.05 Duc Chanh 665 111 16.7
230 17.3 Total 1,327
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.
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Table 3.4. Toxocara infection by gender at study sites
Commune Gender % p Male No. examined 318 No. infected 53 16.7
Duc Phong >0.05 Female 344 66 19.2
Male 323 45 13.9
Female 342 66 19.3 Duc Chanh >0.05
Male 641 98 15.3
Total Female 686 132 19.2 >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
Commune % p
Duc Phong
Duc Chanh
Total <0.05 <0.05 <0.01 Age groups > 15 2 - 15 > 15 2 - 15 > 15 2 - 15 No. examined 435 227 415 250 850 477 No. infected 90 29 79 32 169 61 20.7 12.8 19.0 12.8 19.9 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 662 665 1,327 Seropositive (+) plus clinical symptoms 61 59 120 Duc Phong Duc Chanh Total
9.2 8.9 9.0 Overall human Toxocara infection rate at study sites was 9.0%.
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3.1.3. Associated factors of Toxocara infections Table 3.11. Toxocara infections in dogs at studied sites
Commune % p
Duc Phong No. examined 126 No. infected 42 33.3 >0.05 Duc Chanh 109 35 32.1
235 32.8
Total 77 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
Commune
%
p
Location of soil
No. examined
No. contami nated
Duc Phong 29.5 59 200 >0.05 Duc Chanh 26.0 52 200 At househol ds Total 27.8 111 400
Duc Phong 30.0 3 10 >0.05 Duc Chanh 20.0 2 10 At public placegro unds Total 25.0 5 20
The proportion of soil samples contaminated with Toxocara eggs was 27.8% at households and 25.0% at public playgrounds.
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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
40 40 80 mustard greens
40 40 lettuce 80
40 40 centella 80
40 fish mint 40 80
40 40 80 savory leaves
(%) 2 (5.0) 5 (12.5) 1 (2.5) 3 (7.5) 3 (7.5) 14 (7.0)
(%) 1 (2.5) 4 (10.0) 2 (5.0) 4 (10.0) 2 (5.0) 13 (6.5)
(%) 3 (3.8) 9 (11.3) 3 (3.8) 7 (8.8) 5 (6.3) 27 (6.8)
Total 200 200 400
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
OR (CI 95%)
p
Total 218 Yes
182 No 1.2 (0.7-2.1) > 0.05 Infected (%) 49 (22.5) 34 (18.7) Not infected (%) 169 (77.5) 148 (81.3)
No significant association was found between Toxocara infection in people living in households with and without raising dogs (p>0.05).
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Total p OR (CI 95%) Infected (%)
Table 3.23. Association between eating vegetable and Toxocara infections Regularly eating vegetable
149 Yes
251 1.1 (0.6-1.9) No > 0.05 Not infected (%) 116 (77.9) 201 (80.1) 33 (22.1) 50 (19.9)
the No significant association was found between regularlity of eating vegetable and Toxocara infections (p>0,05). Table 3.24. Association between living habits and Toxocara infections
Total Living habits p Infected (%) OR (CI 95%)
Yes
4.9 (2.5-9.7) Regularly carrying dogs No < 0.01
Yes
2.8 (2-7.0) 48 352 230 170 < 0.01 Regularly playing with soil No
115 Yes
285 2.6 (1.6-4.5) < 0.01 No
87 Yes
1.4 (0.8-1.9) > 0.05 313 No Hand- washing after contacting soil Regularly washing hands before meals 24 (50.0) 59 (16.8) 63 (27.4) 20 (11.8) 38 (33.0) 45 (15.8) 22 (25.3) 61 (19.5)
Not infected (%) 24 (50.0) 293 (83.2) 167 (72.6) 150 (88.2) 77 (67.0) 240 (84.2) 65 (74.7) 252 (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).
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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
17.9
662
119
44.7
< 0.01
32.7
9.9
627
62
< 0.01
16.7
665
111
12.0
> 0.05
14.7
632
93
Interve ntion commu ne Contro l commu ne
Before intervention (1) After intervention (2) Before intervention (3) After intervention (4)
Commune
% Effective index % p
No. infec ted
No. exa mine d 662
9.2
61
42.4
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 Interventi on effect % p 2&4
< 0.01
34.5
627
33
5.3
665
59
8.9
7.9
< 0.05
> 0.05
632
52
8.2
Interve ntion commu ne Contro l commu ne
Before intervention (1) After intervention (2) Before intervention (3) After intervention (4)
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%.
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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
(%)
(%)
91.8
Intervention
61
5
61
95.1
3
(100.0)
(8.2)
(100.0)
(4.9)
Control
59
11
81.4
59
86.4
8
(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
Examined dogs
%
Effective index % p
80.9
No. exa min ed 126
33.0
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Table 3.30. Changed infection rates of Toxocara in dogs after intervention Interventi No. on effect infect % ed p 2&4
<0.01
111
7
6.3
64.4
16.5
109
35
32.1
<0.01
>0.05
97
26
26.8
Interve n tion commu ne Contro l commu ne
Before intervention (1) After intervention (2) Before intervention (3) After intervention (4)
The Toxocara infection rate in dogs at the intervention commune reduced by 80.9% (p<0.01). The intervention effect was 64.4%.
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Commune
%
Table 3.31. Chaged proportions of soil contaminated with Toxocara eggs No. exami ned
No. infe cted
Soil exami ned
Interven tion effect % p 2&4
Effectiv e index % p
200
59
29.5
69.5
Interv entio n
200
18
9.0
< 0.01
50.3
Soil in house holds
< 0.01
200
52
26.0
19.2
Contr ol
200
42
21.0
> 0.05
10
3
30.0
66.6
Interv entio n
10
1
10.0
> 0.05
66.6
> 0.05
10
2
20.0
0
Soil in publi c playg round
Contr ol
10
2
20.0
> 0.05
Before intervention (1) After intervention (2) Before intervention (3) After intervention (4) Before intervention (1) After intervention (2) Before intervention (3) After intervention (4)
Vegetable examined
%
No. examin ed
No. infect ed
Effectiv e index % p
200
7.0
14
71.4
The proportion of soil contaminated with Toxocara eggs in households of the intervention commune reduced from 29.5% to 9.0% (p<0.01); while in the control commne, the proportion reduced from 26.0% to 21.0% (p>0.05). 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 Interven tion effect % p 2&4
200
4
2.0
< 0.05
71.4 <0.05
200
13
6.5
0
200
13
6.5
> 0.05
Interve ntion commu ne Contro l commu ne
Before intervention (1) After intervention (2) Before intervention (3) After intervention (4)
The proportions of vegetable samples contaminated with Toxocara eggs in the intervention commune reduced from 7.0% to 2.0% (p<0.05), while no change in this proportion was found in the control commune. The intervention effect was 71.4%.
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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 answer
Before (1)
95
47,5
Intervention (n=200)
Effective index % p 44,2 < 0,01
Interventio n effect % p 2&4 24,7 < 0,01
Control (n=200)
19,5 > 0,05
After (2) Before (3) After (4)
137 87 104
68,5 43,5 52,0
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<0.01), with the intervention effect of 24.7%.
Table 3.34. Changed knowledge on symptoms of toxocariasis
%
Commune
Correct answer
Intervention effect % p 2&4 23.4 < 0.01
Intervention (n=200) Control (n=200)
Effective index % p 42.3 < 0.01 18.9 > 0.05
Before (1) After (2) Before (3) After (4)
97 138 90 107
48.5 69.0 45.0 53.5
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<0.01), with the intervention effect of 23.4%. 3.2.3.1. Changed practice on toxocariasis control Table 3.35. Changed practice on toxocariasis control
Commune
%
Correct answer
Before (1)
Intervention
Effective index % p 44.1 < 0.01
After (2)
(n=200)
Before (3)
Intervention effect % p 2&4 24.1 < 0.01
Control
After (4)
(n=200)
20.0 > 0.05 93 134 85 102 41.5 67.0 42.5 51.0
In the intervention commune, significant increase was found in the practice on toxocariasis control activities (from 41.5% to 67.0%, p<0.01), with the intervention effect of 24.1%.
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Commune
Yes
%
Before (1)
13.5
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Table 3.39. Changed practice on carrying dogs and treatment of dogs feces Intervent Practice ion effect % p 2&4
Intervention (n=200)
Regularly carrying dogs
61.9
< 0.01
Control (n=200)
After (2) Before (3) After (4)
Before (1)
9 21 20 98
4.5 10.5 10.0 49.0
25.6
Intervention (n=200)
Treatment of dog feces
< 0.01
Control (n=200)
After (2) Before (3) After (4)
129 84 89
64.5 42.0 44.5
Effectiv e index % p 66.7 < 0.01 4.8 > 0.05 31.6 < 0.01 6.0 > 0.05
In the intervention commune, significant reduction was found in the practice of carrying dogs (p<0.01), and the intervention effect was 61.9%. In the same commune, the practice of treating dogs feces increased significantly, with the intervention effect of 25.6%.
Table 3.41. Changed habits of contacting soil and hand washing
Habit
Commune
Yes
%
Effective index % p
Before (1)
115
57.5
Intervention (n=200)
11.3 > 0.05
Regularly contacting soil
Interventi on effect % p 2&4 8.7 > 0.05
After (2) Before (3)
102 115
51.5 57.5
Control (n=200)
2.6 > 0.05
After (4) Before (1)
112 141
56.0 70.5
Intervention (n=200)
21.3 < 0.01
14.4 < 0.05
After (2) Before (3)
171 144
85.5 72.0
Control (n=200)
6.9 > 0.05
Washing hands after contacting soil
After (4) Before (1)
154 160
77.0 80.0
Intervention (n=200)
10.6 < 0.05
177
88.5
6.0 < 0.05
After (2) Before (3)
Washing hands before meal
153
76.5
4.6
Control (n=200)
After (4)
> 0.05
160
80.0
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In the intervention commune, significant reduction was found in the habits of washing hands after contacting soil (from 70.5 to 85.5%, p<0.01), and the intervention effect was 14.4%. Also, the habit of washing hands before meals increased from 80.0 to 88.5% (p<0.05), but the intervention effect was just 6.0%.
Chapter 4. DISCUSSIONS 4.1. Current situation and associated factors of Toxocara infections in humans 4.1.1. Human Toxocara seropositivity
The seropositivity of human toxocariasis was similar to the study conducted by Bui Van Tuan in Binh Dinh and Gia Lai provinces (from 13.05-16.78%), but was lower than those in studies conducted in some countries of the South America, Africa, Asia, and Viet Nam. The differences might come from different test kits used for Toxocara diagnosis and different selection of positive cut-offs. In addition, the differences might be of typical conditions of each country, different timeframe of the studies, number of pets raised in the households, and typical practice of the people raising and taking care of their pets. Therefore, there should be further in-depth studies to be conducted.
The study indicated the seropositive rate in the age group more than 15 years old was higher than the age group from 2 to 15 years old. This result was in line with the study conducted by Nguyen Van Chuong in Dak Lak. Other studies conducted in Viet Nam, Taiwan, and Argentina showed no differences in seropositive rates among age groups. The differences might be due to the settings of the studies, either in urban or rural areas. In rural areas, most of the people are farmers, contacting soil regularly and touching dogs more often, hence putting themselves at higher risk of infections.
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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
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to 4.2% (p<0.05), in
with studies by Nguyen Van Chuong in Binh Dinh and Dak Lak, and by Bui Van Tuan in Binh Dinh and Gia Lai. 4.2. Efectiveness of some intervention measures 4.2.1. Effectiveness of reducing seropositivity and infection rates of human toxocariasis 4.2.1.1. Changed seropositivity and infection rates of human toxocariasis After one year of intervention in two communes, 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); and The intervention effect was 32.7%. Regarding the human Toxocara infections, 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%. Our study was in line with the study conducted by Tran Minh Quy for fascioliasis control in Binh Dinh and Quang Ngai provinces, with the reduction of the infection rates in the full-scale intervention the partly commune from 8.8% intervention commune from 8.4% to 5.4%; but increase in the control commune (from 6.1% to 6.4%). Therefore, compared with the estimated reduction of 30.0% (from 16.0% to 11.0%), our study showed the intervention effects of reducing the seropositivity and infection rates of 32.7% and 34.5%, respectively. 4.2.1.2. Effectiveness of treatment with albendazol on Toxocariasis After one year, the seropositive and infection rates reduced by 86.7% and 90.8%, respectively. This result was in agreement with other studies conducted by Nguyen Van Chuong in Binh Dinh and Dak Lak, by Luong Truong Son in Ho Chi Minh City. This indicated that the treatment fo
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is very effective for
albendazole for a 21-day course Toxocariasis. 4.2.2. Effectiveness of reducing the transmission sources in dogs and outer environment
ivemectin, our injectable revealed study
After intervention, the Toxocara infection rate in dogs at the intervention commune reduced by 80.9% (p<0.01). The intervention effect was 64.4%. Compared with the study by Bui Ngoc Thuy Linh on the effectiveness of deworming for dogs lower using effectiveness. This might be due to our application of oral route, leaving less effectiveness. However in our study, the application of oral medication made it eaiser for households when grinding it with dog meals.
The proportion of soil and vegetable contaminated with Toxocara eggs reduced significantly. This indicated that the solution of deworming for dogs, coupled with health education to change the practice of environmental hygiene, treatment of dogs feces, would reduce the transmission source into the envinroment. The changed proportion of soil contaminated with Toxocara eggs was not significant, despite high effective index (66.0%). This might be due to small sample size (10 samples for 1 commune), which could lead to incorrect statistical calculations. 4.2.3. Effectiveness of health education in improving the the community on knowledge, attitude, and practice of toxocariasis control
After intervention, significant increases were found in the level of knowledge of the risks of infection, symptoms, and control measures in the intervention commune (p < 0,01). Our result was in line with other studies conducted for fascioliasis control by Nguyen Van Chuong and Tran Minh Quy, but the intervention effect in our study was lower. This might be due to
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the fact that much have ever been conducted on fascioliasis, which made the disease known to the community, hence better awareness and practice. Meanwhile, taxocariasis as an newly- emerging tropical disease is not focused in terms of control measures, which catches less attention from the people. However, with the intervention effect from 23.4-24.7%, health education is considered the most effective measures for Toxocara control.
Besides the changes relating to the habits of carrying dogs and washing hands after contacting soil following the intervention, the habit of regularly contacting soil was not changed in our study. This was due to our study was conducted in the rural areas, where people are farmers, often contacting soil. Our study revealed good coordinations of health, veterinary social local government, and other health, education, organizations such as women’s association and farmer association in toxocariasis control campaigns.
Although this is the first study ever conducted to control toxocariasis in Viet Nam, its results revealed reduction of seropositivity in humans, decrease in transmission sources, and increase in level of knowledge, attitude, and practice of the people. The results of this study could eventually inform the initiatives for effective control measures of toxocariasis in the future.
Health education is less expensive; however, it is easy to be implemented, with significant effects of improving the knowledge, attitude, and practice of the community. In this study, the people perceived dogs as the main source of infection, they provided good practice in controlling toxocariasis, which were translated in their more hygienic daily living activities, in better taking care of their dogs, and in regularly deworming for dogs. This proved our control measures were widely accepted
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by the community, which would lay a foundation for a sustainable achieving further outcomes in the future.
Chapter 5. CONCLUSIONS 1. Current situation and associated factors of human Toxocara infections 1.1. Human Toxocara seropositivity and infection rates
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. Toxocara seropositive rates in men and women were 15.3% and 19.2%, respectively; and people aged more than 15 years old have higher seropositive rates than those aged from 2 to 15 years old.
The overall human Toxocara infection rate at study sites was 9.0% (9.2% in Duc Phong, 8.9% in Duc Chanh communes). Main symptoms included urticarial (69.2%), headache (52.5%), abdominal pain (22.5%), and muscle pains (24.2%). 1.2. Associated factors of Toxocara infections
The overall Toxocara infection rate in dogs in two communes was 32.8%, with that at Duc Phong commune of 33.3%; and Duc Chanh of 32.1%. The infection rate reduced by age. The proportion of soil samples contaminated with Toxocara eggs was 27.8% at households and 25.0% at public playgrounds. The proportion of vegetable contaminated with Toxocara eggs was 6.8%.
Low levels of knowledge, attitude, and practice of the community under study were found in the study communes, with less than 50% of the surveyed people having correct answers.
Toxocara infection was found to have close associations with regularly carrying dogs (OR= 4.9; CI 95%: 2.5-9.7);
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regularly contacting soil (OR= 2.8; CI 95%: 2.0-70); not washing hands after contacting soil (OR= 2.6; CI 95%: 1.6-6.5). 2. Effectiveness of intervention measures in toxocariasis control 2.1. Effectiveness of reducing seropositivity and infection rates of human toxocariasis The seropositivity reduced from 17.9% to 9.9% at the intervention commune; with the intervention effect of 32.7%.
The infection rate of toxocariasis was reduced from 9.2% to 5.3% at the intervention commune, with the intervention effect of 34.5%. 2.2. Effectiveness of reducing the transmission sources in dogs and outer environment
The Toxocara infection rate in dogs at the intervention commune significantly reduced from 33.0% down to 6.3%., with the intervention effect of 64.4%.
The proportion of soil contaminated with Toxocara eggs in households of the intervention commune reduced from 29.5% to 9.0%, with the intervention effect of 50.3%.
in improving the the community on
The proportion of vegetable contaminated with Toxocara eggs reduced from 7.0% to 2.0%, with the intervention effect of 71.4%. 2.3. Effectiveness of health education knowledge, attitude, and practice of toxocariasis control
In the intervention commune, significant increase was found in the level of knowledge of the risks of infection, and better attitude of toxocara control, with the intervention effects from 23.4% to 24.7%.
Also in the same commune, significant increases were found in the practice of deworming for dogs (from 13.9% to 50.9%, intervention effect of 205.4%), treatment of dogs feces
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(from 49.0% to 64.5%, intervention effect of 25.6%), washing hands after contacting soil (from 70.5% to 85.5%, intervention effect of 14.4%); meanwhile, reduction in the practice of carrying dogs was found (from 13.5% to 4.5%, intervention effect of 61.9%).
Chapter 5. RECOMMENDATIONS
Related bodies such as
1. For the Ministry of health The national helmthiasis control program or project should be established, with the helmthiniasis surveillance system being set up from central to grass-roots levels. institutes of malariology, parasitology and 2. For the entomology, and provincial centers for disease control and prevention Studies on situation and associated factors of toxocariasis in various epidemiological settings should be continued, especially areas where dog and cat raising is popular. Intervention measures for toxocariasis control should be applied to provinces, with focus on health education messages via social media, leaflets, posters. 3. For health facilities, related bodies, and the community local government, social organizations, sectors of education and veterinary health should be involved in health education campaigns for toxocariasis control in the community. Messages of health education should be maintained on the broadcasting systems, coupled with direct talks in schools or integrated in other health care programs. Risks of infections and practice of self protection, environmental sanitation, and regular deworming for dogs should be practiced in a regular manner.
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LIST OF PUBLISHED ARTICLES IN RELATION TO THE THESIS
1. Bui Van Tuan, Nguyen Van Chuong, Ly Chanh Ty, Tran Phuong Duyen, Vu Sinh Nam (2017), “Seropositive rate of toxocariasis in human and associated factors in Mo Duc district, Quang Ngai province, 2016”. Journal of Preventive Medicine; Vol. 27, No. 8-2017, pp. 572-578.
2. Bui Van Tuan, Nguyen Van Chuong, Vu Sinh Nam (2017), “Infection rates of Toxocara spp. in dogs and Toxocara eggs in soil and vegetables at some study sites of Mo Duc district, Quang Ngai province in 20166”, Journal of Malaria and Parasite Diseases Control; Special Issue (96) /2017, pp. 241-246.
3. Bui Van Tuan, Nguyen Van Chuong, Ly Chanh Ty, Vu Sinh Nam (2018), “Effectiveness of some intervention measures for toxocariasis control in Mo Duc district, Quang Ngai province”, Journal of Preventive Medicine, Vol. 28-No. 2-2018, pp. 38-44.
