Nonlinear pattern of pulmonary tuberculosis among migrants at entry in Kuwait: 1997–2006

BMC Public Health BioMed Central Research article Open Access Nonlinear pattern of pulmonary tuberculosis among migrants at entry in Kuwait: 1997–2006 Saeed Akhtar*1 and Hameed GHH Mohammad2 Address: 1Department of Community Medicine and Behavioural Sciences, Faculty of Medicine, Kuwait University, PO Box 24923, Safat 13110, Kuwait and 2Ports and Borders Health Division, Ministry of Health, PO Box 32830, Rumaithiya 25410, Kuwait Email: Saeed Akhtar* - ; Hameed GHH Mohammad - * Corresponding author Published: 30 July 2008 BMC Public Health 2008, 8:264 doi:10.1186/1471-2458-8-264 Received: 2 November 2007 Accepted: 30 July 2008 This article is available from: http://www.biomedcentral.com/1471-2458/8/264 © 2008 Akhtar and Mohammad; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: There is a paucity of published data on the pattern of pulmonary tuberculosis among migrant workers entering Middle Eastern countries particularly Kuwait. The objectives of this study were to use routine health surveillance data i) to estimate the prevalence of pulmonary tuberculosis among migrant workers at entry in Kuwait and ii) to determine the occurrence of any time trends in the proportions of pulmonary tuberculosis positive workers over the study period. Methods: The monthly aggregates of daily number of migrants tested and the number of pulmonary tuberculosis cases detected during routine health examinations of migrant workers from tuberculosis high-prevalence countries were used to generate the monthly series of proportions (per 100,000) of pulmonary tuberculosis cases over 120 months between January 1, 1997 and December 31, 2006 and analysed using time series methods. Results: The overall prevalence (per 100,000) of documented pulmonary tuberculosis cases among screened migrants was 198 (4608/2328582). Year-specific prevalence (per 100,000) of tuberculosis cases consistently declined from 456 (95% CI: 424 – 490) in 1997 to 124 (95% CI: 110 – 140) in 2002 before showing a steady increase up to 183 (95% CI: 169–197) in 2006. The secondorder polynomial regression model revealed significant (P < 0.001) initial decline, followed by a significant (P < 0.001) increasing trend thereafter in monthly proportions of tuberculosis cases among migrant workers. Conclusion: The proportions of documented tuberculosis cases among migrant workers showed a significant nonlinear pattern, with an initial decline followed by a significant increasing trend towards the end of the study period. These findings underscore the need to maintain the current policy of migrants' screening for tuberculosis at entry. The public health authorities in Kuwait and perhaps other countries in the region may consider complementing the current screening protocol with interferon-J assays to detect migrants with latent Mycobacterium tuberculosis infection. An appropriate curative or preventive chemotherapy of detected tuberculosis cases may help in further minimizing the risk of local transmission of M. tuberculosis, while contributing in global efforts to control this public health menace. Page 1 of 8 (page number not for citation purposes) BMC Public Health 2008, 8:264 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 control programmes can achieve a high level of treatment success 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 tuberculosis notifications has been reported from many developed countries [7,8]. This disturbed declining trend has been attributed, in part, to the spread of human immunodeficiency 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 nationals. Kuwait has a relatively low incidence of tuberculosis with annual notification rate of 24 active tuberculosis cases per 100,000 of population [12]. Resident nonnationals account for about 75% of these active tuberculosis 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 therefore, seems to play little role in tuberculosis epidemiology. 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 Mycobacterium tuberculosis transmission from non-nationals to nationals, since a large proportion of migrants from tuberculosis 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 tuberculosis high to low incidence countries has been recognized 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]. Elsewhere immigrants from high-incidence countries to http://www.biomedcentral.com/1471-2458/8/264 developed and Middle Eastern countries reportedly have high prevalence of tuberculosis [19,20], but there is a paucity 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 screening of these workers over the past ten years gave us an opportunity in this study not only 1) to estimate the prevalence of (...truncated)