Battling tuberculosis in an island context with a high burden of communicable and non-communicable diseases: epidemiology, progress, and lessons learned in Kiribati, 2000 to 2012

Objectives: To examine the epidemiology of tuberculosis (TB) in Kiribati from 2000 to 2012, document lessons learned, and recommend ways to mitigate the burden of TB in Kiribati. Methods: A descriptive study was performed using data on TB case notifications, prevalence, incidence, mortality, and treatment outcomes from global reports and data files. Progress towards meeting the Millennium Development Goal TB target (to reduce TB incidence by 2015) and the Regional Strategy to Stop Tuberculosis in the Western Pacific 2011–2015 targets (to reduce TB prevalence and mortality by half by 2015 relative to the level in 2000) was examined. Results: TB case notifications and the estimated incidence and prevalence have increased in Kiribati since 2000. From 2000 to 2012, Kiribati reported a total of 3863 TB notifications; in 2012, the case notification rate was 343/100 000 population. The majority (89%) of TB patients complete treatment and/or are cured, and the estimated TB mortality rate has remained relatively stable at around 16/100 000 population. HIV testing of TB patients has increased over recent years from 8% of notifications tested in 2003 to 43% tested in 2012. Of all 818 tests, only four (0.5%) patients were confirmed HIV-positive. Drug-resistant TB has been detected in a small number of cases. Conclusions: TB rates continue to increase in Kiribati and the 2015 goals for TB control are unlikely to be met. This is probably due to the complex mix of risk factors present in Kiribati, including smoking, diabetes, alcohol use, crowded living, and poverty. A comprehensive approach to address these risk factors is needed to mitigate the burden of TB in Kiribati

Australian planner

Tuberculosis incidence rates in Kiribati are among the highest in the Western Pacific Region, however the genetic diversity of circulating Mycobacterium tuberculosis complex strains (MTBC) and transmission dynamics are unknown. Here, we analysed MTBC strains isolated from culture positive pulmonary tuberculosis (TB) cases from the main TB referral centre between November 2007 and October 2009. Strain genotyping (IS6110 typing, spoligotyping, 24-loci MIRU-VNTR and SNP typing) was performed and demographic information collected. Among 73 MTBC strains analysed, we identified seven phylogenetic lineages, dominated by Beijing strains (49%). Beijing strains were further differentiated in two main branches, Beijing-A (n = 8) and -B (n = 28), that show distinct genotyping patterns and are characterized by specific deletion profiles (Beijing A: only RD105, RD207 deleted; Beijing B: RD150 and RD181 additionally deleted). Many Kiribati strains (59% based on IS6110 typing of all strains) occurred in clusters, suggesting ongoing local transmission. Beijing-B strains and over-crowded living conditions were associated with strain clustering (likely recent transmission), however little evidence of anti-tuberculous drug resistance was observed. We suggest enhanced case finding amongst close contacts and continued supervised treatment of all identified cases using standard first-line drugs to reduce TB burden in Kiribati. Beijing strains can be subdivided in different principle branches that might be associated with differential spreading patterns in the population

Neighbour joining tree combining 24 loci MIRU-VNTR and spoligotyping data.

<p>Neighbour joining tree (left panel) based on the copy numbers of 24 loci MIRU-VNTR (right panel, spoligotyping results whereby a repeat region's presence or absence is indicated by a black box or white box respectively) of the 73 strains investigated. The tree was calculated using the MIRU-VNTR<i>plus</i> server (Distance Measure: Dc: Cavalli-Sforza and Edwards, 1967: Dc <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0055423#pone.0055423-CavalliSforza1" target="_blank">[15]</a>). Seven lineages were identified including 71 out of the 73 strains (97%), while two strains could not be allocated to a strain family. Classification of the strains into the different phylogenetic lineages is visualized by color coding, key on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0055423#pone-0055423-g002" target="_blank">Figure 2</a>.</p

IS<i>6110</i> clustering patterns, DNA fingerprinting pattern and MTBC 15-9 classification of Kiribati isolated Beijing strains.

<p>The classification of Beijing strains in two major branches is further supported by completely different IS<i>6110</i> fingerprint patterns showing a higher copy number for Beijing-B isolates (&gt;17 bands) compared Beijing-A isolates (&lt;13 bands).</p

Demographic details of study participants.

1<p>Chi square test.</p>2<p>Wilcoxon Rank Sum test.</p>3<p>Fisher's Exact test.</p>4<p>All available HIV serology was negative. In Kiribati, HIV testing is generally performed using the Determine HIV1/2 kit as an initial screening assay (Alere, Queensland, Australia).</p

Factors associated with sputum sample being culture positive.

1<p>Chi square test.</p>2<p>Wilcoxon Rank Sum test.</p

Minimum Spanning Tree of 24 loci MIRU-VNTR data.

<p>Minimum Spanning Tree, based on the 24 loci MIRU-VNTR typing data of 73 analysed Kiribati strains. The size of each circle is proportional with the number of MIRU-VNTR types belonging to a particular complex. Classification of the strains into the different phylogenetic lineages is visualized by color coding.</p