Tuberculosis in children
Childhood TB has been neglected for decades and has long been an overlooked area within global TB control. Poor ascertainment and reporting of cases of TB prevent accurate estimation of the European burden of disease in children.
TB in children most commonly results from household contact with someone with active TB, and represents ongoing transmission of Mycobacterium tuberculosis in the community. Infants and young children have an increased risk of infection following exposure and progress more readily from infection to active TB. In the absence of intervention, infants have a 50–60% risk of disease in the first year following infection. Young children more commonly present with disseminated disease and miliary TB and have an increased risk of death. Even low bacillary loads in children can lead to acute and severe illness, be it respiratory or disseminated; this is particularly the case in children less than 2 years of age. The generally accepted assumption is that qualitative and quantitative differences in the immune responses to mycobacterial infection between adults and children determine the outcome.
The total number of childhood TB cases in Europe in 2010 was about 11 000, with 3365 reported cases in children aged 0–4 years and 7549 reported cases in children from 5–15 years. The proportion of TB cases differs greatly between western and eastern European countries. The proportions of children with TB in eastern Europe aged 0–4 years and 5–15 years are expected to be two and four times higher, respectively, than those in western Europe.
The geographical distribution of TB in children is presented in figure 7.
The exact number of children with TB in eastern European countries is not known, but of greater concern is the lack of information regarding multidrug-resistant (MDR) and extensively drug-resistant (XDR) cases in children in Europe. Outside Europe, the highest rates of paediatric MDR-TB are reported in low-income countries and in some regions the incidence of MDR-TB has risen sharply in the past two decades. For instance, in Western Cape, South Africa, the proportion of culture-confirmed cases of MDR-TB has tripled in the past 15 years from 2.3% to 7.3% of all TB cases.
Given the overwhelming burden of TB and the vulnerability of young children to active TB disease, it is surprising that TB does not feature among the leading causes of death in children. The explanation might be the protection afforded by the bacille Calmette–Guérin (BCG) vaccination, although the protective efficacy of BCG is suboptimal.
Confirmation of the diagnosis of TB in children may be difficult, since collecting specimens of spontaneously produced sputum is problematic, although gastric aspiration and sputum induction (with or without laryngopharyngeal suction) are feasible alternative methods of collection. The tuberculin test and the interferon-γ release assay fail to differentiate M. tuberculosis infection from active disease, especially in vaccinated children. When a combination of clinical, radiological, laboratory and histopathological findings are consistent with a diagnosis of TB and there is epidemiological evidence of exposure to TB, an accurate diagnosis is possible in most cases.
In the future, better and more simple diagnostic tests must be developed to enable a rapid and 100% reliable diagnosis of TB. Furthermore, information on the prevalence and incidence of TB, MDR-TB and XDR-TB in children is urgently required for the whole European continent.
More information on TB can be found in chapter 17.