The World Health Organization (WHO) has declared March 24, 2016 as World Tuberculosis (TB) Day . Over the month of March, the Global Health Office will be publishing a series of blog posts about TB in hopes of raising awareness of its worldwide impact. WHO’s “End TB Strategy” has a goal of ending the TB epidemic by 2030, by targeting poverty, improving testing and treatment, ending stigma and discrimination, and driving research and innovation. Put simply, TB is not yet a disease of the past, but if we unite and focus our efforts, we can make TB history.
Last week we talked about diagnosing TB, and the importance of determining an appropriate treatment course along with that diagnosis. But how is TB treated, and why is drug resistance an issue with TB in particular?
Although those with latent TB infection do not present symptoms, and cannot spread TB bacteria to others, treatment can still be provided to stop them from developing TB disease. This step is important in eliminating and controlling TB around the world, but should only be initiated once the possibility of TB disease has been excluded. In the United States, four treatment regimens are approved, using combinations of isoniazid, rifampicin and rifapentine. Treatment for latent TB can last anywhere from 3 months to 9 months, necessitating between 12 and 270 doses (minimum) of anti-TB drugs .
Treating those with active TB disease is a much more pressing matter, as they have the potential to spread the disease to others. Treatment regimens for active TB disease can last between 6 and 30 months depending on resistance, a process which burdens patients and treatment providers alike . With a treatment course this long, some patients inevitably fail to complete the full regimen, for many reasons including finances, social pressures and inadequate access to proper treatment. To provide a glimpse at the financial burden of TB, each case in Canada cost the healthcare system $47,290 . This can lead to acquired drug resistance, which can then be passed on to others when the infected person, coughs, sneezes or spits, releasing TB bacteria into the air .
There are two types of drug-resistant TB: multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). MDR-TB bacteria does not respond to (at least) the two most widely used and powerful first line TB drugs: isoniazid and rifampicin . XDR-TB involves resistance to isoniazid and rifampicin, in addition to resistance to any of the fluoroquinolones (ofloxacin, etc.), and to at least one of three injectable second-line drugs (amikacin, capreomycin or kanamycin) . Both MDR-TB and XDR-TB take longer than regular TB to treat (at least 18 months) and have lower treatment success rates. Furthermore, patients often experience more harsh side effects from treatment, leading to increased hospitalization . In order to maximize the potential for positive treatment outcomes, it is important that further tests are undertaken after initial diagnosis to determine whether bacteria is drug-resistant, and provide appropriate treatment .
According to the WHO Global TB Report, in 2014 an estimated 3.3% of new TB cases and 20% of previously treated cases had MDR-TB. More than half of these cases occur in India, China and the Russian Federation. Additionally, an estimated 190,000 people died of MDR-TB in 2014. As of 2015, XDR-TB had been reported in 105 countries. The map below shows the number of patients in these countries with laboratory-confirmed XDR-TB who started treatment in 2014 .
In response to treatment non-adherence, and to combat the spread of drug-resistant TB, the directly observed therapy, short-course (DOTS) strategy was developed by WHO in 1994. Health workers meet with patients regularly to help with treatment, adherence, and to provide support and education. This strategy also advocates for increased allocation of domestic and international funding and resources to combat TB . Tuberculosis is also highlighted in two recent worldwide strategies, the WHO End TB Strategy, and the UN Sustainable Development Goals (SDGs), which will be discussed in our next post.