BMC Public Health 2008, 8:264 http://www.biomedcentral.com/1471-2458/8/264
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(page number not for citation purposes)
Background
Tuberculosis remains one of the leading infectious causes
of death globally, killing nearly 2 million people a year
[1]. Sub-Saharan Africa has the highest incidence (290 per
100000), but the most populous countries of Asia have
the largest numbers of cases and together account for
more than half of the global burden [2]. Tuberculosis con-
trol programmes can achieve a high level of treatment suc-
cess and have been shown to be associated with a decline
in reported burden of disease [3-6]. However, for the past
two decades, a levelling off or a reverse trend in tubercu-
losis notifications has been reported from many devel-
oped countries [7,8]. This disturbed declining trend has
been attributed, in part, to the spread of human immun-
odeficiency virus, multidrug-resistant tuberculosis,
homelessness, deterioration of living conditions and
health care delivery, increased drug abuse, immigration
from tuberculosis high to low prevalence countries
[7,9,10]. Nonetheless, reasons for this phenomenon are
complex, differ from one country to another, and have not
been entirely elucidated [11].
Kuwait is a small oil-rich Arabian country in the Persian
Gulf region of the Middle East, having a total population
of 2.5 million (Kuwaiti: 42%; Non-Kuwaiti 58%), with a
gender ratio (male/female) of 1.04 at birth among nation-
als. Kuwait has a relatively low incidence of tuberculosis
with annual notification rate of 24 active tuberculosis
cases per 100,000 of population [12]. Resident non-
nationals account for about 75% of these active tubercu-
losis cases per year [12,13], and nearly 1% of these are
identified as multidrug-resistant tuberculosis cases [14].
Illegal immigration to Kuwait is almost negligible there-
fore, seems to play little role in tuberculosis epidemiol-
ogy. Tuberculosis incidence in Kuwait showed a steady
decline from 1965 to 1989. Subsequently, however, there
was a rise of 2.3% per year from 1989 to 1999, both
among nationals and non-nationals suggestive of Myco-
bacterium tuberculosis transmission from non-nationals to
nationals, since a large proportion of migrants from tuber-
culosis high-burden countries live and work in Kuwaiti
homes as domestic workers [12]. Notwithstanding the
possibility of M. tuberculosis transmission from migrants
to Kuwaiti nationals, there is a lack of empirical evidence
for such local transmission [15].
The epidemiological importance of migration from tuber-
culosis high to low incidence countries has been recog-
nized for several years; the main countermeasure has been
implementation of screening programs for immigrants at
the time of arrival [16,17]. But it not clear that to what an
extent the increased immigration from high-incidence
countries contributes to an increased risk of tuberculosis
in host community of low-incidence countries [18]. Else-
where immigrants from high-incidence countries to
developed and Middle Eastern countries reportedly have
high prevalence of tuberculosis [19,20], but there is a pau-
city of published data on the prevalence of tuberculosis in
migrant workers entering Kuwait. Here, we take advantage
of the routine screening of migrants for tuberculosis,
upon arrival in Kuwait from tuberculosis-endemic
regions, to do a first large-scale quantification of the
tuberculosis status of this work population. Specifically,
the cumulated data on the results of tuberculosis screen-
ing of these workers over the past ten years gave us an
opportunity in this study not only 1) to estimate the prev-
alence of tuberculosis in this population of workers, but
also 2) to ascertain if any significant time trend or changes
had occurred in the prevalence of tuberculosis among
these workers during the recent past.
Methods
Setting and study population
Migrants constitute about 80% of the labour force in
Kuwait, and majority of them usually have a low educa-
tional attainment. These migrants originate from tubercu-
losis high-burden countries predominantly from
Southeast Asia, Eastern Mediterranean and African
regions wherein prevalence (per 100,000) of tuberculosis
ranges from 152 to 547 [21]. There is large turn over of
these workers; every year thousands of them leave and
new ones arrive in Kuwait. Of the migrants, 46% are 20 to
44 year old and predominantly live as single, mainly
because of their inability to fulfil a legal requirement of
minimum wages to be able to bring their families [22,23].
Health services are free for all citizens and residents in
Kuwait. In public sector, health-care system is made up of
six administratively independent health-care sites; each
comprises a general hospital, a health center, specialized
clinics and dispensaries [24]. In Kuwait, a single tubercu-
losis control unit and the Kuwait National Central Labo-
ratory under the Ministry of Health are responsible for
prevention, diagnosis, treatment, case recording/report-
ing, contact tracing and treatment supervision under
DOTS (Directly Observed Therapy, Short-course) strategy.
On diagnosis of tuberculosis, all patients are offered treat-
ment using first-line anti-tuberculosis drugs including iso-
niazid, rifampicin, ethambutol, and streptomycin based
on drug sensitivity pattern [15].
Data source
Monthly aggregates of test results for diagnosis of pulmo-
nary tuberculosis among migrants entered in Kuwait
between January 1, 1997 and December 31, 2006 were
available for this study. These migrants predominantly
come from India (31%), Bangladesh (14%), Sri-Lanka
(14%), Egypt (12%), Indonesia (9%), Philippine (5%),
Pakistan (5%) and 10% from other countries including
those from African counties such as Tanzania, Mali, Gam-
bia, Sudan (12%) [25,26]. Routine consensual medical