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

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)

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:

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

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)

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:

- 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, 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

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

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

- Sample size of vegetable: 200 samples of vegetable at each study site

- Sample size for KAP survey: One person per household (200 household/commune)

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

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

3.1.1 Human Toxocara seropositivity

Table 3.3 Human Toxocara seropositivity at studied sites

Commune

Blood samples for ELISA

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

Table 3.4 Toxocara infection by gender at study sites

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

3.1.2 Human Toxocara infections

Table 3.8 Human toxocara infections at studied sites

examined

Seropositive (+) plus clinical symptoms

3.1.3 Associated factors of Toxocara infections

Table 3.11 Toxocara infections in dogs at studied sites

Table 3.13 Proportion of soil samples contaminated with

Table 3.15 Toxocara eggs contamination on vegetable

No

examine

d

No contaminat

ed (%) mustard

Table 3.22 Association between dog raising and Toxocara infections

Dog raising Infected

(%)

Not infected (%)

Table 3.23 Association between eating vegetable and Toxocara infections

Regularly

eating

vegetable

Infected (%)

Not infected (%)

Total

OR (CI 95%)

Table 3.24 Association between living habits and Toxocara infections

Living habits Infected

(%)

Not infected (%)

Total

OR (CI 95%)

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

exam ined

No

infect

ed

% Effective index %

p

Interven tion effect %

intervention (4)

632 93 14.7

After the intervention, the seropositivity reduced from 17.9% to 9.9% (p<0.01) at the intervention commune and reduced from 16.7% to 14.7% (p>0.05) The intervention effect was 32.7%

Table 3.26 Changed infection rates of toxocariasis after intervention

exa mine

d

No

infec ted

% Effective index %

intervention (4)

632 52 8.2

The infection rate of toxocariasis was reduced from 9.2% to 5.3% (p<0.01) at the intervention commune, and from 8.9% to 8.2% (p>0.05) at the control commune The intervention effect was 34.5%

3.2.1.2 Effectiveness of treatment with albendazol on Toxocariasis

Table 3.27 Effectiveness of albedazol for the treatment of toxocariasis

Before

(%)

After (%)

Effective index (%)

Before (%)

After (%)

Effective index (%) Intervention 61

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

exa min

intervention (4)

97 26 26.8

The Toxocara infection rate in dogs at the intervention commune reduced by 80.9% (p<0.01) The intervention effect was 64.4%

Table 3.31 Chaged proportions of soil contaminated with Toxocara eggs

No

infe cted

200 18 9.0

Contr

ol

Before intervention (3)

200 52 26.0

19.2

> 0.05 After

10 1 10.0

Contr

ol

Before intervention (3)

10 2 20.0

0

> 0.05 After

intervention (4)

10 2 20.0

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 No

intervention (4)

200 13 6.5

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%

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

answer

% Effective index %

Control

(n=200)

Before (3) 87 43,5 19,5

> 0,05 After (4) 104 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

answer

% Effective index %

p

Intervention effect %

3.2.3.1 Changed practice on toxocariasis control

Table 3.35 Changed practice on toxocariasis control

answer

% Effective index %

p

Intervention effect %

(n=200)

Before (3) 85 42.5 20.0

> 0.05 After (4) 102 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%

Table 3.39 Changed practice on carrying dogs and treatment of dogs feces

e index

%

p

Intervent ion effect

Table 3.41 Changed habits of contacting soil and hand washing