July 23, 2014
Mycobacterium tuberculosis, a small bacterial pathogen that most commonly causes lung disease, is one of mankind s most loyal companions. Having developed in Africa 70,000 years ago, the pathogen is thought to have hitched a ride out of the continent through human migration. The ability of M. tuberculosis to spread has always depended on human living and working conditions; the last couple centuries in particular brought about significant increase in population density that allowed the disease to spread more rapidly. Antibiotics have further altered the evolutionary playing field and helped the emergence of many novel drug-resistant strains.
Despite the adaptive ability of the pathogen, for many people all over the world, especially those that have access to good sanitation and healthcare systems, the disease is merely of historical importance. This phthisis or consumption as it used to be called is more commonly encountered in novels about the 19th century than on the streets of developed countries. This depiction gives a false impression of the current situation: tuberculosis (TB) incidence has always been elevated in less developed regions, with many people harboring a latent infections, but incidence skyrocketed in the 1990s with the spread of the human immunodeficiency virus (HIV). Normally only 10% of latent carriers develop an active form of TB, but compromised immunity enables the bacterium to easily tackle the host s immune protection. In fact, TB is the most common fatal opportunistic infection among HIV-positive patients, according to the WHO.
Southern Africa, with its high HIV/AIDS burden, also has unsurprisingly high levels of TB infection, averaging 1003 new cases annually per 100,000 South Africans. Unfortunately, the presence of HIV infection is not the only risk factor. Occupationally contracted TB has been a significant problem for gold miners working in the ultra-deep operations of southern Africa. During their underground shift, mineworkers breathe in fine silica dust, which is deposited in their lungs and causes an irreversible fibrosis called silicosis. Because of the tissue it affects, silicosis (often synergistically with HIV) increases the chance that the sick mineworker also develops active TB. It is therefore no surprise that estimates of TB incidence among South African mineworkers range from 3,000 to 6,000 patients per 100,000 mineworkers, making it a community with one of the highest incidence rates of TB in the world second only to South Africa’s incarcerated population.
For a long time, mineworkers have been the metaphorical sentinel canary birds that signal the presence of the health risks that are hidden deep below the surface. Despite the large number of cases of occupationally contracted TB and its international significance due to migrant workers, this epidemic remained relatively neglected until 2010, when the issue came under international scrutiny. Thanks to a joint effort by the health ministers of all southern African countries, the World Bank, the WHO, and many other stakeholders, a number of projects aimed at programmatic improvement are being designed and implemented in the mines and the mineworkers communities alike. This effort aims to estimate the true burden of the disease with focused research and create a robust knowledge base that could inform future policy changes.
Nevertheless, there remains much work to be done. Next steps include better spatial estimation of the burden across the region as well as mapping of drug resistance and analysis of its temporal trends in order to help focused and efficient resource allocation. If the level of commitment is maintained over the long term, it will positively influence not only the mineworkers and their communities, but also the rest of southern Africa.
Veronika Lipkova is a Research Intern currently based in CDDEP’s New Delhi office.
Homepage image via Jan Truter/Flickr.
