March 24 is World Tuberculosis (TB) Day, but most of us don't know about it. TB in India has somehow slipped from the public imagination. Although much is known about TB, from its origin to the tracing of the bug, there are still enormous scientific challenges that remain unanswered.
One of the biggest challenges is a lack of timely and correct diagnostic tools. The most widely used method to diagnose TB in India - sputum smear microscopy - misses more than half of all cases. Ineffective and inaccurate diagnostics not only lead to the patient suffering but also speeds up the spread of the infection. Alternatively, misdiagnosis can lead to six months of unnecessary toxic treatment. In the private sector, ineffective TB diagnostics is a lucrative market. Patients in the private sector are commonly subjected to serological (antibody) tests that have poor sensitivity and specificity for TB diagnosis. This is despite the fact that the World Health Organisation (WHO) has issued guidelines against the use of serological tests. There are new and more effective diagnostic technologies approved by the WHO that have been introduced globally. India needs to make immediate efforts to improve techniques for diagnosing TB in the public sector by introducing new technologies.
The second challenge is the lack of an effective vaccine for TB. Once a successful vaccine, Bacillus Calmette-Guérin (BCG) is the only vaccine available today. However, it has become almost ineffective. Unfortunately there are no new vaccines that exist, reducing the options we have to fight the disease. Nearly all the anti-TB drugs that have been discovered have failed to the extent that drug resistance has emerged. As a result, TB is far from defeated and continues to be a deadly killer.
A novel vaccine will be a major contribution in the fight against TB. Vaccines are cheap and the most effective tools against infectious diseases. Now that the genome sequences of a large number of strains of TB are available and many new developments have taken place in vaccinology, in principle it should not be difficult to develop effective TB vaccines. There are several new vaccines candidates in various stages of clinical trials. There is hope that in the next five to 10 years we may have an effective vaccine against TB. It is imperative that drugs and vaccine trials are conducted in India because such trials require a large number of cohort and durations for their completion. India needs to come forward scientifically and as a policy framework develop such sites for the trials for vaccines developed indigenously or by others. Discovering an effective bio marker, which can truly reflect the TB status in the host will be of immense value for these trials.
India's growing burden of drug resistant TB is another key challenge. All drug resistance in TB is man-made, caused by inappropriate use of anti-TB drugs. Drug resistance develops when the TB drug regimen is poorly administered, or when patients stop taking their medicines before the disease has been fully treated. Multi-drug resistant TB (MDR-TB) can transform into extensively drug resistant TB (XDR-TB) through inadequate or interrupted treatment with second-line anti-TB drugs. That means that providers who use non-standard regimens prescribe non-quality assured drugs, make patients pay for drugs which they may not be able to afford, and provide treatment without ensuring patient adherence through supportive supervision. Though there are clear regulations on the sale and dispensation of over-the-counter sale of anti-TB drugs, they remain weakly implemented and large-scale distribution of anti-TB drugs has become rampant. It is also important to remember that the treatment for MDR-TB is complex, expensive and has terrible side effects. India and China are currently home to 50% of the globe's multidrug-resistant TB (MDR-TB) cases and this represents a growing challenge for India's TB control.
A vital scientific challenge in TB is to understand the latent nature of the disease. In endemic countries a large number of people have latent TB but very few develop active TB. Clearly the bug has adapted very well to the human host and can exist in the host lifelong. How the bug adapts still remains unknown. An understanding of the host parasite interactions is a major scientific question and given the development of several modern technologies, it is possible to understand the molecular mechanism. However, clearly it is emerging that the problem is much more complex and scientifically fascinating.
There has been a tremendous push from the government towards research, development and control of TB. The Revised National Tuberculosis Control Programme DOTS initiative has been very successful and is being hailed as one of the most successful public health initiatives in India. Over the next few years, the National TB Programme aims to provide universal access to quality diagnostics and treatment for all as well as detect and treat MDR cases in India. There is a need to allocate finances to Indian laboratories and scientists to fund research in various aspects of TB including drug and vaccine development and bio marker discovery. It's important to discover devices and medicines to not only detect TB in time but also treat people who are falling prey in large numbers to this preventable disease.
Virander S Chauhan is director and leader for the Malaria Research Group at the International Centre for Genetic Engineering and Biotechnology (ICGEB)
(The views expressed by the author are personal.)