Importance of tuberculosis control to address child survival

Abstract

Tuberculosis commonly aff ects young children (<5 years) in countries that have high rates of child mortality. The global public health focus to control tuberculosis has traditionally aimed to reduce transmission through early case-fi nding and eff ective treatment of the most infectious cases. Young children have historically been excluded from this focus, since their contribution to tuberculosis transmission is believed to be small. In the past decade, national tuberculosis programmes in highburden settings have given increased attention to the challenges of childhood tuberculosis. In 2012, World TB Day focused on children for the fi rst time. This attention is likely to increase further as the WHO Global Tuberculosis Programme’s ambitious post-2015 tuberculosis control strategy seeks to engage the entire health sector, including maternal and child health. Within the Millennium Developmental Goal (MDG) framework, tuberculosis control and its related targets are framed within MDG 6, and yet are also relevant to MDGs 4 and 5 (child and maternal mortality) and MDG 1 (undernutrition). Improvement of child survival is a major global health priority but tuberculosis is not regarded as important in that context. However, we believe that the relevance of tuberculosis to child survival will become increasingly apparent over the next decade, especially in countries where tuberculosis control remains diffi cult and high rates of Mycobacterium tuberculosis transmission are sustained. Recognition of the relevance and challenges of tuberculosis to child survival is growing. The 2012 WHO Global Tuberculosis Report was the fi rst edition of this report to provide global estimates of the burden of childhood tuberculosis. The diffi culties in provision of accurate estimates of childhood tuberculosis are widely acknowledged and include challenges of case detection, diagnostic accuracy, and poor recording and reporting practices. Vital registration data, in which causes of death are coded according to the two latest revisions of the International Classifi cation of Diseases (ICD; underlying cause of death: ICD-10 A15–A19, equivalent to ICD-9: 010–018), were used to produce a global estimate of childhood mortality attributed to tuberculosis in children not infected with HIV, with the most recent estimate of 74 000 deaths in 2012. Because these deaths represent only about 1% of the estimated total deaths in children globally in 2012, tuberculosis is not regarded as a major contributor to child mortality. However, there are important limitations to the estimate of 74 000 child deaths from tuberculosis. First, tuberculosis is also an important cause of death in children living with HIV, but for these deaths HIV is registered as the underlying cause and tuberculosis as a contributory cause. Since a third of countries with vital registration systems report only the underlying causes of death and not contributory causes to WHO, vital registration data cannot be used to estimate the number of tuberculosis deaths in people living with HIV. Further, vital registration data are available for only 3% of global child deaths and are not available in most tuberculosisendemic countries. The risk of death due to tuberculosis in children is highest for those younger than 5 years. However, accurate characterisation of tuberculosis-related deaths in young children can be challenging because the clinical features of tuberculosis are not specifi c. Tuberculosis in young children is usually a clinical diagnosis that is not confi rmed microbiologically, especially in tuberculosisendemic areas with scarce resources. Therefore, estimation of the contribution of tuberculosis to deaths in young children that have been attributed to pneumonia or malnutrition, either as the direct cause or as comorbidity, is a challenge. Findings from clinical studies show that tuberculosis is common in African children with severe pneumonia. Investigators of a study from Uganda of 270 children with WHO-defi ned severe pneumonia reported that 19% had a clinical diagnosis of tuberculosis and 6% had culture-confi rmed tuberculosis. Pooled analysis of autopsy studies from fi ve African countries of children who died with respiratory disease showed that 11% of 473 children with HIV and 8% of 338 children not infected with HIV had tuberculosis. The fi ndings need to be interpreted with caution because of possible sample bias. These clinical and autopsy studies were mainly from tertiary urban centres representing the most critically ill children, and the direct cause of death in these children is diffi cult to ascertain. However, the fi ndings suggest that tuberculosis could be a more common cause of morbidity and mortality in children with pneumonia than is recognised. 1·3 million children were estimated to have died from pneumonia in 2011, and almost half of these deaths were children in Africa. If then, for example, around 10% of child pneumoniarelated deaths were due to tuberculosis, the present estimates of deaths in children due to tuberculosis would more than double. Tuberculosis can cause substantial weight loss, but data to quantify its contribution to childhood malnutrition are scarce. Investigators of studies from Bangladesh and South Africa report very similar results, despite representing low and high HIV-endemic settings. Tuberculosis was microbiologically confi rmed in 4–6% of children with severe malnutrition and clinically diagnosed in an additional 16–17%. In 2011, an estimated 500 000 deaths in children were associated with severe wasting, and infectious diseases, such as pneumonia, were the immediate causes of these deaths. Lancet 2014; 383: 1605–07