Malaria control in Vietnam: the Binh Thuan experience
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Transcript of Malaria control in Vietnam: the Binh Thuan experience
Malaria control in Vietnam: the Binh Thuan experience
Nguyen Van Nam1, Peter J. de Vries2, Le Van Toi1 and Nico Nagelkerke3
1 Binh Thuan Provincial Malaria Station, Phan Thiet, Binh Thuan Province, Vietnam2 Division of Infectious Diseases, Tropical Medicine and AIDS, Academic Medical Center, Amsterdam, The Netherlands3 Department of Medical Statistics, Leiden University Medical Center, Leiden, The Netherlands
Summary objective The National Malaria Control Program (NMCP) in Vietnam is based on application of
insecticide-treated bed nets (ITNs), spraying of insecticides and early microscopic diagnosis of malaria
and treatment (EDTM) with artemisinin drugs. This study explores the implementation of the NMCP at
provincial level and its impact on malaria incidence (mi) and prevalence in Binh Thuan in southern
Vietnam.
methods Data on implementation of EDTM, distribution of ITNs, annual mi and Plasmodium index
(pi) were derived from intervention logbooks and surveillance records kept by the provincial Malaria
Station since 1988. The relation between interventions and the change of pi over time was analysed with
Generalized Estimating Equations.
results Control activities focused on the highly endemic zones where ITNs were distributed free of
charge to ethnic minority groups, including twice yearly re-impregnation, from 1992 onwards. This
almost completely replaced insecticide spraying. Complete ITN coverage of these groups was achieved in
1995, constituting 40% of the entire population. In all malaria endemic communes, primary health care
posts were consecutively upgraded or installed, mainly between 1992 and 1995, offering EDTM with
artemisinin drugs free of charge. Before 1994, mi peaked to over 50/1000, pi to over 16% in the highly
endemic zones. In 1998, these had decreased to below 9/1000 and 4% respectively. The effects of the
interventions could not be discerned with statistical significance.
conclusion Malaria incidence and prevalence declined significantly in Vietnam, possibly due to the
malaria control efforts, but coinciding with rapid socioeconomic changes.
keywords malaria, Vietnam, early diagnosis, treatment, artemisinins, insecticide-treated bed nets,
health policy
Introduction
Malaria control currently focuses on two interventions, the
use of insecticide-treated bed nets (ITNs), and early
diagnosis and treatment of malaria (EDTM). These are the
pillars of the global malaria control campaign (WHO
2000). ITN programmes effectively prevent infection in
low and high malaria transmission regions, can even
reduce transmission if coverage is high, but can be
expensive, potentially compromising their sustainabili-
ty.(Verle et al. 1999). EDTM denotes a wide range of
passive and active case-finding activities and therapeutic
strategies that all aim at halting progress of disease to
severe stages (WHO 2000).
The recent Vietnamese malaria control experience, much
quoted but hardly studied in a quantitative fashion,
suggests that an integrated approach based on community
participation can be successful (Ettling 2002). Vietnam is
endemic for malaria, especially in its mountainous-forested
areas. Between reunification in 1975 and 1985 the number
of malaria cases declined, followed by a resurgence with
thousands of fatalities annually (Thi Phan et al. 1999). The
health care system was weak and supply of antimalarial
drugs irregular. Chloroquine and sulphadoxine/pyrimeth-
amine (SP) were the mainstay of treatment yet only
available in limited amounts. They were increasingly
replaced by quinine because of widespread multi drug
resistance. Severe malaria was common but parenteral
treatment with quinine was not available at the primary
health care level.
The new National Malaria Control Program (NMCP)
was adopted in 1991, based on ITNs, spraying of residual
insecticides and EDTM. National malaria morbidity and
mortality figures showed a steady decline since 1994
(Nguyen 1999; Warrell 2001). A similar pattern can be
observed at provincial level (Ettling 2002).
The implementation of the NMCP at provincial level is
delegated to provincial Malaria Stations (MS) which are
Tropical Medicine and International Health
volume 10 no 4 pp 357–365 april 2005
ª 2005 Blackwell Publishing Ltd 357
also responsible for surveillance. In Binh Thuan, a province
in the mountainous parts of southern Vietnam, MS started
recording malaria incidence (mi) and prevalence before the
launching of the NMCP, as an adjunct to the standard
health information system. In this study, we explore this
valuable data source with the aim to document and analyse
the relation between malaria control efforts and the
changes in mi and prevalence in Binh Thuan.
Data sources and methods
Study site
Binh Thuan (Figure 1) is traversed by a forested mountain
ridge in north–south direction, parallel to the coast. The
average annual rainfall ranges from 1000 to 1400 mm
mostly between May and November. Binh Thuan com-
prises eight administrative districts, including the capital
Phan Thiet, and 106 communes. The total population rose
from 767 000 in 1989 to 1 041 000 in 2000 (population
density 120/km2), of which three-quarters live in rural
areas (data from Provincial Statistics Department). Half of
the provincial domestic product is generated by agricul-
ture, forestry and fishery, 20% by industry and construc-
tion (increasing) and 30% by services (increasing). The
average income rose from US$217 in 1995 to US$278 in
1998 in urban areas and from US$137 to US$230 in rural
areas.
Malaria epidemiology
The Vietnamese epidemiological classification of malaria is
based on a compilation of criteria (Vu Thi Phan et al.
1999) The epidemiological classification of communes in
Binh Thuan is shown in Table 1. Improvement, sustained
for 5 consecutive years, leads to reclassification. Figure 1
shows the geographical position of communes in Binh
Thuan and their epidemiological classification until 1994.
Malaria transmission is mainly confined to the moun-
tainous forested regions inhabited by poor tribes, of the
highly endemic zones 3 and 4, but occasionally extends to
other villages in these zones. Especially remote ethnic
1 2
3 4
Low endemic communes:
Highly endemic communes:
•Hanoi
•
Ho Chi MinhCity
Phan Thiet
Figure 1 Map of Vietnam and Binh Thuan Province and their epidemiological classification until 1994.
Tropical Medicine and International Health volume 10 no 4 pp 357–365 april 2005
N. Van Nam et al. Malaria control in Vietnam
358 ª 2005 Blackwell Publishing Ltd
minority communes often lacked any health care facility
until the early 1990s. Inhabitants had to seek curative
care at other communes’ health facilities. Outside zones 3
and 4 malaria is mainly imported by people exposed to
mosquitoes in the forest. In 1999, a program was
launched to further the development of forested regions,
leading to increased migration and a resurgence of
malaria.
Malaria control interventions
The implementation of the NMCP at provincial level is
delegated to the MS. The MS is part of the provincial
health services but also accountable to the National
Institute of Malariology, Parasitology and Entomology
(NIMPE). Malaria control activities focused on zones 3
and 4 and were organized through the district hospitals and
health posts, which are run by the respective People’s
Committees. In principle, all communes have their own
health post with responsibilities for diagnosis and treat-
ment of malaria, prevention and surveillance. Until
recently health posts were staffed by professionals of
different educational backgrounds such as second degree
doctors, nurses, midwives and technicians.
The new 1991 national malaria policy aimed at revital-
izing existing or installing new health posts in all com-
munes, and providing subsidized essential drugs (‘social
drugs’) such as artemisinin drugs for malaria. To finance
these measures, cost sharing was introduced. However,
poor people were exempted from this and continue to
receive free health care from the public sector. This
effectively covers all ethnic minorities and most other
inhabitants of the highly endemic malaria regions (zones 3
and 4).
Early diagnosis and treatment of malaria
The implementation of the NMCP in Binh Thuan was a
stepwise process of consecutively upgrading and staffing
health posts. Supplementary to the NMCP, Binh Thuan
MS provided all health posts in zones 3 and 4 with
equipment, staff and training for microscopic malaria
diagnosis, including refresher courses twice yearly. This
coincided with the introduction of artemisinin drugs. Thus,
in the following our interpretation of EDTM includes early
EDTM with artemisinin drugs, all free of charge, 24 h/day,
within walking distance for the entire population.
In many instances, the first participation of a health post
in randomized-treatment studies was grasped as an
opportunity to launch EDTM, thereby combining efforts,
sharing resources and ensuring quality control and
adequate documentation of treatment (Giao et al. 2001,
2002, 2003, 2004; Le et al. 1997; Hung et al. 2004).
Prior to the introduction of EDTM, health posts did not
prescribe artemisinin drugs; quinine was the mainstay of
treatment for falciparum malaria and chloroquine for
vivax malaria. Between 1992 and 1994 artemisinin deriv-
atives were introduced in all districts. Artemisinin and later
artesunate were mainly used in combination with meflo-
quine as a single dose treatment (500 mg plus 500 mg
mefloquine and later 200 mg artesunate plus 750 mg
mefloquine), but also 5-day courses of monotherapy
artesunate or artemisinin were used. In 1999–2000, a fixed
combination of dihydroartemisinin, piperaquine, trimeth-
oprim and primaquine (CV8�) became the first-line
treatment (Giao et al. 2004).
A national policy to upgrade all health posts and to have
at least one university-trained medical doctor among the
staff of all health posts started later, when EDTM had
Table 1 The classification of malaria epidemiology in Binh Thuan Province
Epidemiogicalzone
Plasmodiumindex (%) Main vector/BR
Descriptives
Public healthcare system Economic situation
I 0 Number of anophelines Relatively well High (urban area)II <0.5, mainly
P. vivaxAnopheles minimus,BR < 0.4
Good Stable (rural area)
III >0.5, P. falciparum >P. vivax
Mainly A. minimus,BR > 0.4 some A. dirus
Average or weak Average or low(forests and mountains,
some ethnic minorities)
IV >1, mainly
P. falciparumA. minimus and A. dirus,BR > 0.4, DDT resistance
Weak/absent Low (like III with slash
and burn agriculture,mainly ethnic minority
population)
Plasmodium index, the proportion of positive blood smears in malaria surveys; biting rate, bites of anophelines per hour per person;
DDT, dichlorodiphenyltrichloroethane; BR, biting rate.
Tropical Medicine and International Health volume 10 no 4 pp 357–365 april 2005
N. Van Nam et al. Malaria control in Vietnam
ª 2005 Blackwell Publishing Ltd 359
already been installed at all health posts. Between 1995
and 2000 the number of fully qualified doctors doubled.
Malaria treatment in the private sector
In Binh Thuan, treatment for malaria was an exclusive
activity of the public sector until 1999. Most formulations
of artemisinin drugs and mefloquine are listed as ‘social
drugs’ and thus not allowed in the private sector. In
addition, since 1990, following national principles, the
Binh Thuan MS has been persuading the private sector to
refer suspected malaria cases to the public health posts,
which were made more attractive by offering their services
free. Thus, the contribution of the private sector to malaria
treatment was limited.
In zones 1 and 2, where people tended to be more
affluent, the (more developed) private sector retained a role
in malaria treatment, albeit small. Since 1999, the national
policy again allowed the private sector to sell antimalarial
agents except social drugs. In that same year CV8� was
introduced but it was only available as a social drug to be
used in the public health sector.
Vector control
Residual spraying and ITNs were introduced into zone 3
and 4 communes, starting in 1992. Before that, bed nets
were not used in ethnic minority communes and rarely in
the ethnic Vietnamese communes. Spraying and distribu-
tion of ITNs were discontinued as soon as a commune was
reclassified to epidemiological zone 2 but surveillance
continued for 5 years. Spraying and re-impregnation of
ITNs was done twice a year, just before and after the rainy
seasons, concurrent with health education and surveillance
campaigns. In 1992 and 1993, dichlorodiphenyltrichloro-
ethane (DDT) was used for spraying. Because of the rapid
decline of the mi after the introduction of ITNs, spraying
was largely abandoned after 1995.
To combat the resurgence of malaria in 1999, spraying
of k-cyhalothrin (ICON�) and occasionally deltamethrine
was resumed. The main reason for the resurgence was that
settlers migrated into the forested zones and often had to
stay in semipermanent huts or sheds. ITNs were not always
suitable in these conditions or available in sufficient
quantities for the expanded households. This was covered
by spraying residual insecticides. From 1997 insecticide
sensitivity tests were performed irregularly, mainly to guide
the purchase of insecticides (WHO 1992) The main
vectors Anopheles dirus and A. minimus were sufficiently
sensitive throughout. However, the residual effects were
short-lived especially on brick walls, prompting the
replacement of k-cyalothrin by a-cypermethrin in 2002.
The ITNs were rectangular (height 150 cm, length 180–
190 cm, width 100–140 cm for two persons or 70–80 cm
for single persons), of knitted Denier 70–100 nylon multi-
filament and mesh 156 (12 · 13 holes/in.2 or hole size 1.2–
1.5 mm), mostly blue or green (white was avoided because
of its association with mourning). ITNs were produced in
Vietnam and purchased by the NMCP at approximately
US$3. They were distributed by the MS free of charge to all
inhabitants of the ethnic minority villages in zones 3 and 4.
The ITNs were re-impregnated by soaking with per-
methrin-emulsified concentrate. In 1999, a permethrin
formulation appeared to be substandard and as then
deltamethrin suspension concentrate became the main
insecticide. The distribution of free ITNs to the ethnic
minority villages in zones 3 and 4 and the number of ITNs
per household were gradually increased, with available
resources, from one ITN for every four to one for every
two household members. The proportion of the population
protected by ITNs was calculated as the number of people
living in a house with at least one ITN per four household
members. ITN distribution campaigns always aimed at
providing ITNs to all households of an ethnic minority
hamlet/village.
More affluent villages inhabited by ethnic Vietnamese
did not receive ITNs, even if they were located in zones 3
or 4. Inhabitants of these villages were encouraged to
purchase ITNs themselves, following the health promotion
campaigns, but we have no data on the coverage rate of
self-purchased ITNs and do not know how often people re-
impregnated their bed nets. During the study period,
dengue vector control was in its infancy and unlikely
affected malaria epidemiology.
Health education and community participation
Education sessions on recognition and prevention of mal-
aria, guided by periodic knowledge, attitude and practice
(KAP)-surveys, were organized for the population in zones 3
and 4, starting with the Cham minority in 1992, with
support fromCARE International.Other groups followed in
1993 and 1994. These sessions were integrated with the
twice yearly ITN re-impregnation campaigns and surveys.
Several health programmes in Vietnam, including the
malaria and dengue control programmes, the family plan-
ning programme, the malnutrition programme and the
HIV/AIDS prevention programme, make use of co-workers.
They are lay members of a commune, who receive short
extra training in certain health problems. Some co-workers
participate in more than one programme. To date there are
380 health co-workers working in 77 villages.
In some highly endemic communes, co-workers partici-
pated in the malaria control programme. Initially, they
Tropical Medicine and International Health volume 10 no 4 pp 357–365 april 2005
N. Van Nam et al. Malaria control in Vietnam
360 ª 2005 Blackwell Publishing Ltd
received a 1-week training course in order to assist in
health communication and supervise the use and coverage
of ITNs. Later their training and responsibilities were
expanded to include early detection of febrile patients,
taking blood smears and referring patients to the health
posts, and participation in the surveillance and ITN
distribution and re-impregnation campaigns.
Malaria data sources
Between 1988 and 1994 the recording of mi, separately
from the general health management information system,
was introduced at the public health posts. The Vietnamese
public health system has been used to recording data and
even at a time when facilities for diagnosis and treatment of
malaria were not optimal, malaria cases were recorded.
The diagnosis was often based on clinical grounds or by
sending a blood slide for confirmation to the MS or district
hospital. Where microscopy was available, the causative
parasite was also recorded. In communes without health
posts, notification was non-existent and in the low endemic
zones it was less complete.
These data, collected monthly by the MS, were the basis
for this study. Annual mi was calculated as the total of
annually reported cases divided by the total population of
the communes which participated in notification. At the
higher levels of the health care system, recording of malaria
cases has long been in place. The data on hospital
admissions for malaria, severe malaria, and malaria-
attributable mortality were extracted from the district and
provincial hospital records.
Malaria prevalence
Surveillance of malaria prevalence is carried out by the MS
and by the commune health posts. Classic malariometric
surveys are held by the MS in the highly endemic zones (3
and 4), at the end of the dry and of the wet season (Hung
et al. 2002). To measure local transmission in a village,
they commonly sample those present there, including the
majority of children and women. Because of the rather
uniform methodology of these surveys, their results were
used for further study. Health posts in zones 3 and 4 also
took fixed annual quotas of blood smears. Because of the
variable nature of the sampled population these data were
not used for analysis.
Analysis and statistics
The association between the malaria control measures and
the malaria data was studied, based on the previously
explained assumption that the interventions, EDTM and
ITNs/spraying, can be interpreted as instantaneous changes
introduced in all communes in a stepwise fashion. We
hypothesized that the malaria control interventions had a
significant effect on the decline of prevalence per commune.
The interventions were entered as nominal value dividing
before and after the start of the intervention. The first
introduction of the ITNs in a commune,with a density of one
ITN per four members of every household, was taken as the
start of this intervention. The later increase of the number of
ITNs per household was not incorporated in the analysis.
The effect of the interventions on malaria prevalence
data was analysed on a time scale, taking dependencies
between observations from the same health posts into
account using Generalized Estimating Equations (GEE;
sas version 8.2). Year and epidemiological classification
were incorporated in the model as potential confounders.
Other changes over time, such as socioeconomic improve-
ments, usually do not follow a stepwise pattern and are
thus less likely to confound the outcome. The surveys at
the end of the dry season and the surveys at the end of the
wet season were analysed separately, taking the blood
smear results as dependent variable and the number of
slides per survey as a weight variable.
In some ethnic minority communes, the erection of a
new health post before 1995 coincided with the introduc-
tion of EDTM. This confounded the reported incidence. In
addition, the introduction of EDTM probably caused some
redirection of help seeking from the private sector to public
health services. Therefore, incidence was not further
analysed.
Results
Interventions
By the end of 1995, all health posts of the malaria endemic
zones 3 and 4 offered EDTM free of charge (Figure 2). In
the other zones diagnosis and treatment were less regulated
by the health authorities.
The population protected by ITNs/spraying programme,
calculated as the number of subjects living in a household
protected by the ITNs programme divided by the total
population of the communes, is shown in Figure 2. After
the introduction of ITNs additional spraying was limited,
focusing on new comers in the high transmission. This
maximally concerned 12 villages with a total population of
approximately 14 000.
Malaria incidence
The number of notified cases of malaria is shown in
Figure 3. Because of incomplete data from communes
Tropical Medicine and International Health volume 10 no 4 pp 357–365 april 2005
N. Van Nam et al. Malaria control in Vietnam
ª 2005 Blackwell Publishing Ltd 361
without health posts before 1994, and the redirection of
health-seeking behaviour after the introduction of EDTM,
there is a spurious increase in incidence. The reverse is seen
in the district hospital data, which also served as primary
health facilities in the absence of commune health posts
before 1994. After 1994, the hospital data became more
stable and show that severe disease and mortality declined
rapidly after 1994, faster than the total of admitted cases.
Malaria prevalence
Malaria prevalence, shown in Figure 4, started to decline
significantly after 1994. Notably, epidemiological zone 2
data only reflect communes or hamlets, being surveyed
after a recent epidemiological reclassification. The provin-
cial average of the non-endemic zones 1 and 2 is much
lower.
Association between interventions and malaria data
Analysis by GEE of the prevalence data supports what can
be gleaned from Figure 4, viz a significant decline in
malaria prevalence after 1994 in the surveys in the wet
as well as in the dry season. A significant independent effect
of either intervention (ITNs or EDTM) could not be
confirmed.
Discussion
We explored the success of Vietnam’s malaria control
interventions at provincial level during the last decade.
Although the interventions jointly may have contributed to
the improvements, they could not be attributed to any
individual element of the control activities. Health service
data are difficult to interpret. There are many factors
influencing the reported incidence, which cannot be
quantified and which may confound statistical analysis. In
this study, the incidence data collected before 1994 are also
subject to these drawbacks. However, from 1994 onwards,
the data are reliable. The Vietnamese public health services
have a tradition of recording data and the number of
malaria patients seeking help outside the public health
posts after the introduction of EDTM was probably very
small. The people in the endemic regions were very eager to
start using the well-tolerated and highly effective artemis-
inin drugs and there was prohibitive pressure on the private
sector to be involved in malaria diagnosis and treatment.
Prevalence data are also subject to errors, notably a bias
in selecting subjects for surveys. The population which is
routinely surveyed by the MS may contain a dispropor-
tionate number of women and children: men perform most
of the outdoor work and tend to be absent at surveys, but
are more often exposed to forest-related malaria. However,
the trends observed in this study paralleled the decline of the
malaria prevalence observed in a series of surveys in one
ethnic minority hamlet, which aimed at surveying the entire
population, including males, and a 2-year prospective study
carried out in the Mekong Delta region (Hung et al. 2002;
Erhart et al. 2004a).
With respect to EDTM, the approach was to improve
awareness and responsiveness of both the population and
the health care sector to the extent that EDTM was
19901992
19941996
19982000
2002Years
19931995
19971999
20011991
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1989
residual spraying, highly endemic communes,
Only ITNs, highly endemic communes
ITNs, low endemic communesHighly endemic communes Low endemic communes
% population protected by:
% commune health posts offering EDT:
ITNs + Spraying of residual insecticides, highly endemic communes
Figure 2 Progress of malaria control
interventions in Binh Thuan, Vietnam.
Population protected by insecticide-treatedbed nets free of charge or residual spraying
( , residual spraying in highly endemic
communes; , insecticide-treated bed nets
(ITNs) in highly endemic communes; ,ITNs and residual spraying in highly
endemic minority communes; , ITNs in
low endemic communes) and proportion of
health posts providing early diagnosis andtreatment of malaria ( , highly endemic
communes; , low endemic communes).
Tropical Medicine and International Health volume 10 no 4 pp 357–365 april 2005
N. Van Nam et al. Malaria control in Vietnam
362 ª 2005 Blackwell Publishing Ltd
permanently available within walking distance to most of
the population. It should be noted that the centralized
introduction of EDTM by the health authorities in Binh
Thuan was possible because the private sector was almost
non-existent in the regions inhabited by the ethnic minority
groups and because these groups, being recognized as
vulnerable, are used to participate in government-supported
programmes. In other regions, the private sector may be
much stronger, requiring different approaches (Erhart et al.
2004a).
Hospital admission data show a decrease after 1989
which is probably an artefact. In the absence of a health
post, district hospitals tend to take over much of the
notification. The increase until 1994 is a real reflection of
0
2
4
6
8
10
12
14
16
18
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002d w d w d w d w d w d w d w d w d w d w d w d w
Highly endemic communesLow endemic communes
Years, dry season (d ) and wet season (w )
Mal
aria
pre
vale
nce
in s
urve
ys (
%)
Figure 4 Malaria prevalence in Binh
Thuan, Vietnam. Prevalence of malariaparasite carriers in twice yearly malario-
metric surveys. h bars, highly endemic
communes; bars, low endemiccommunes.
0
10
20
30
40
50
60
19891990
19911992
19931994
19951996
19971998
19992000
20012002
Com
mun
e he
alth
pos
t-in
cide
nce
(/10
00)
Hos
pita
l dat
a
Highly endemic communes Low endemic communes
0
50
100
150
200
250
Severe malariaHospital admissions for malaria (x100)
Malaria attributablemortality
Hospital data:
Commune health post incidence:
69%
33% 31
%19
%86
%45
%90
%
93%
97%
100%
100%
100%
100%
100%
100%
100%
100%
72%
76%
81%
92%
94%
91%
87% 98
%
98%
100%
100%
Figure 3 Malaria incidence, severe mor-
bidity, mortality and prevalence in Binh
Thuan, Vietnam. Malaria incidence at
primary health care level and in-hospitalmalaria attributable morbidity and
mortality. On the left ordinate the incidence
at health posts: h bars, highly endemic
communes; bars, low endemic com-munes. The proportion of commune health
posts reporting incidence (%) is indicated
by the numbers on top of the bars. On theright ordinate the hospital data: triangles,
hospital admissions for malaria (·100);asterisk (*), number of cases with severe
malaria; crosses, malaria attributablemortality.
Tropical Medicine and International Health volume 10 no 4 pp 357–365 april 2005
N. Van Nam et al. Malaria control in Vietnam
ª 2005 Blackwell Publishing Ltd 363
the increased burden of malaria attributable disease in
Vietnam in those years. The marked decrease of severe
morbidity, preceding the decline of total malaria hospital
admission rate after 1994, suggests that timely diagnosis,
treatment and referral improved. There is prior evidence
that an antimalarial treatment policy can affect mortality.
When chloroquine resistance became widespread in West
Africa, mortality increased (Trape et al. 1998). In contrast,
other methods of delivering some form of EDTM by
mothers, school teachers or community health workers
significantly reduced mortality in children under 5 (Kidane
& Morrow 2000). Other methods of delivering early
diagnosis and treatment by community health workers or
teachers have also proved successful.
In Vietnam, affordable and sustainable distribution of
twice yearly re-impregnated ITNs is the mainstay of vector
control. ITNs offer individual protection thereby reducing
morbidity and mortality, especially in infants, but carry-
over to the community by reducing transmission has also
been demonstrated (D’Alessandro et al. 1995; Lengeler
2002; Gimnig et al. 2003; ter Kuile et al. 2003a,b; Phillips-
Howard et al. 2003). Re-impregnation enhances the effic-
acy (D’Alessandro et al. 1995; Gimnig et al. 2003). It is
not easily adopted as a routine practice and therefore
requires some form of central delivery free of charge (Snow
et al. 1999). Nevertheless, untreated nets are better than
none and social marketing of bed nets reduced under 5
mortality in a holoendemic area (Clarke et al. 2001;
Schellenberg et al. 2001). Concerns about rebound
mortality after introduction of ITNs have not been
substantiated (Binka et al. 2002; ter Kuile et al. 2003a;
Phillips-Howard et al. 2003; Diallo et al. 2004).
The epidemiological and socioeconomic conditions in
Binh Thuan were such that a strategy of covering only the
population in highly endemic foci, i.e. the ethnic minority
hamlets and villages, and offering EDTM to all com-
munes, was effective in reducing malaria. However, the
separate effects of EDTM and ITNs could not be
discriminated, probably because they were put into place
in a rather narrow time span. They coincided with the
rapid transformation of a society committed to develop-
ment, education and community participation. Further-
more, other factors came into play. For example, 1998
was a dry year and 1999 very wet. Excessive rains
promote mosquito growth (especially A. dirus). Para-
doxically, droughts also tend to increase mi as farmers try
to compensate their reduced rice crop by forest work. In
addition, the epidemiology of malaria in Southeast Asia is
patchy, correlated with the distribution of forest. This
reduced transmission by targeting the risk population, the
ethnic minority groups, which constitutes only 40% of
the total population in zones 3 and 4. Moreover, the
main vectors, A. minimus and A. dirus, in these
communes were relatively easily deterred by ITNs
because most inhabitants went to bed very early before
the introduction of electricity. Although hard to quantify,
ongoing deforestation may also have affected malaria
transmission. Similarly hard to quantify is the effect of
socioeconomic improvements, such as road and electrical
grid constructions.
Malaria transmission in Binh Thuan is nowadays mainly
confined to the forested regions, requiring permanent
vigilance and special approaches (Erhart et al. 2004b).
This is illustrated by the resurgence of incidence in 1999,
which can largely be explained by increased movement of
people into the forested regions, especially workers in
infrastructural projects such as new roads and hydroelec-
tric plants. Many of these workers come from other
provinces, live in groups in temporary camps, do not apply
appropriate preventive measures and were difficult to reach
for the health services. To date these groups receive special
attention by the MS.
Which lessons can be learned from this example from
Vietnam? The rapid reorganization of the health sector in
Vietnam and, with respect to malaria, the rapidly achieved
success, may have frustrated the statistical inference to
evidence-based health policy. However, the key features of
the Vietnamese approach can easily be distinguished. These
are a flexible and responsive organization, community
participation and surveillance, and clear objectives shared
by health service and population. Human migration to and
from the endemic foci in the forested regions remains a
challenge for malaria control and a permanent pressure on
resources put for adequate malaria control and will. These
general features, rather than details, indicate the way
forward.
Acknowledgement
Thanks are due to Dr Allan Shapira for his valuable
suggestions on the first draft of this manuscript.
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Authors
Nguyen Van Nam (Vietnamese corresponding author) and Le Van Toi, Malaria Control Center, 133A Hai Thuong Lan Ong, Phan
Thiet, Binh Thuan Province, Vietnam. E-mail: [email protected]
Peter J. de Vries (English corresponding author), Division of Infectious Diseases, Tropical Medicine and AIDS, Academic Medical
Center F4-217, PO Box 22700, 1100 DE Amsterdam, The Netherlands. E-mail: [email protected]
Nico Nagelkerke, Department of Medical Statistics, Leiden University Medical Center, Postbox 9604, 2300 RC Leiden, The
Netherlands
Tropical Medicine and International Health volume 10 no 4 pp 357–365 april 2005
N. Van Nam et al. Malaria control in Vietnam
ª 2005 Blackwell Publishing Ltd 365