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

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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: Public Health
Major code: 62 72 03 01

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 (20162017).


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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:
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%.


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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, 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 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
2
(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 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


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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:
- 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 2 p 1  p   z p1 1  p1   p2 1  p2 



2

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


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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
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.


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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
<0.05
2
15
227
29
12.8
Phong
> 15
415
79
19.0
<0.05
Duc Chanh
2 - 15
250
32
12.8
> 15
850
169
19.9
<0.01
Total
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.
Seropositive (+)
%
examined 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%.


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3.1.3. Associated factors of Toxocara infections
Table 3.11. Toxocara infections in dogs at studied sites

No.
No.
Commune
%
examined
infected
Duc Phong
126
42
33.3
Duc Chanh

109

35

32.1

p
>0.05

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

At
househol
ds

At public
placegro
unds

Commune

No.
examined

No.
contami
nated

%

Duc Phong

200

59

29.5

Duc Chanh

200

52

26.0

Total

400

111

27.8

Duc Phong

10

3

30.0

Duc Chanh

10

2

20.0

Total

20

5

25.0

p

>0.05

>0.05

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
Kinds of

No.

vegetable

examine
d

No.
contaminat
ed
(%)

Duc Chanh
No.
examine
d

No.
contaminat
ed
(%)

Total
No.
examine
d

No.
contaminat
ed
(%)

mustard
greens

2
1
3
40
40
80
(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
(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).
Yes

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Table 3.23. Association between eating vegetable and Toxocara infections

Regularly
eating
vegetable

Not
Total
OR
p
infected
(CI 95%)
(%)
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).
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).
Living habits


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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

Interve
ntion
commu
ne
Contro
l
commu
ne

Before
intervention (1)
After
intervention (2)
Before
intervention (3)
After
intervention (4)

No.
exam
ined

No.
infect
ed

%

Effective
index %
p

662

119

17.9

44.7

627

62

9.9

< 0.01

665

111

16.7

12.0

632

93

14.7

> 0.05

Interven
tion
effect %
p 2&4
32.7
< 0.01

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.
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%
(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

(%)
Intervention
Control

61

5

(100.0)

(8.2)

59

11

91.8
81.4

(100.0) (18.6)
Total

120

16

(%)
61

3

(100.0)

(4.9)

59

8

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
min
ed
p
%
ed
p 2&4
80.9
Interve Before
126
42
33.0
n tion intervention (1)
<0.01
commu After
111
7
6.3
64.4

ne
intervention (2)
16.5
Contro Before
109
35
32.1
<0.01
l
intervention (3)
>0.05
commu After
97
26
26.8
ne
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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Table 3.31. Chaged proportions of soil contaminated with Toxocara eggs
Soil
exami
ned

Soil
in

house
holds

Commune

No.
exami
ned

No.
infe
cted

%

Effectiv
e index
%
p

Interven
tion
effect %
p 2&4

Interv
entio
n

Before

200
59 29.5
69.5
intervention (1)
After
200
18
9.0
< 0.01
50.3
intervention (2)
< 0.01
Contr Before
200
52 26.0
19.2
ol
intervention (3)
After
200
42 21.0 > 0.05
intervention (4)
Soil Interv Before
10
3
30.0
66.6
in
entio intervention (1)
publi n

After
10
1
10.0 > 0.05
66.6
c
intervention (2)
> 0.05
playg Contr Before
10
2
20.0
0
round ol
intervention (3)
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% (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
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

4

2.0

200

13

6.5

200

13

6.5

Effectiv
e index
%
p

Interven
tion
effect %

p 2&4

71.4
< 0.05
0

71.4
<0.05

> 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), while no change in this proportion was found in the
control commune. The intervention effect was 71.4%.


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

Intervention
(n=200)
Control
(n=200)

Correct

answer

%

Before (1)

95

47,5

After (2)
Before (3)
After (4)

137
87
104

68,5
43,5
52,0

Effective
index %
p
44,2
< 0,01

Interventio
n effect %

p 2&4
24,7
< 0,01

19,5
> 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<0.01), with the intervention effect of 24.7%.
Table 3.34. Changed knowledge on symptoms of toxocariasis
Commune

Intervention
(n=200)
Control
(n=200)

Before (1)
After (2)
Before (3)
After (4)

Correct
answer

%

Effective
index %

p

Intervention
effect %
p 2&4

97
138
90
107

48.5
69.0
45.0
53.5

42.3
< 0.01
18.9
> 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<0.01), 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

Before (1)

Correct
answer

%

Effective
index %
p

Intervention
effect %
p 2&4

93
41.5
44.1
< 0.01
After (2)
134
67.0
(n=200)
24.1
Before
(3)
85
42.5
20.0

< 0.01
Control
>
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<0.01), with the intervention effect of 24.1%.
Intervention


18
Table 3.39. Changed practice on carrying dogs and treatment of dogs feces
Practice

Regularly
carrying
dogs

Commune

Intervention
(n=200)
Control
(n=200)

Treatment

of dog
feces

Intervention
(n=200)
Control
(n=200)

Yes

%

Effectiv
e index
%
p

Intervent
ion effect
%
p 2&4

Before (1)

27

13.5

After (2)
Before (3)

After (4)
Before (1)

9
21
20
98

4.5
10.5
10.0
49.0

66.7
< 0.01

61.9

After (2)
Before (3)
After (4)

129
84
89

64.5
42.0
44.5

Yes

%

Effective
index %
p

Before (1)

115

57.5

After (2)
Before (3)

102
115

51.5
57.5

11.3
> 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<0.01), 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

Regularly
contacting
soil

Intervention
(n=200)

Washing
hands
after
contacting
soil

Intervention
(n=200)

Washing
hands
before
meal

Intervention
(n=200)

Control
(n=200)

Control
(n=200)

Control
(n=200)

2.6
> 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<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.


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


21
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
commune from 8.8% to 4.2% (p<0.05), in the partly
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


22
albendazole for a 21-day course is very effective for
Toxocariasis.
4.2.2. Effectiveness of reducing the transmission sources in
dogs and outer environment
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
using injectable ivemectin, our study revealed lower
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
knowledge, attitude, and practice of the community on
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


23
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 newlyemerging 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
health, education, local government, and other social
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


24
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);

25
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%.
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 in improving the
knowledge, attitude, and practice of the community on
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