On the eve of World TB Day, Dr Manoj Kumar Goel, Director & Head, Department of Pulmonology, Pulmonary Critical Care & Sleep Medicine, Fortis Memorial Research Institute, highlights that it is a major public health concern and points out that not enough has been done to control its incidence
Tuberculosis is no longer a disease afflicting only the poor. Now it also thrives on the offshoots of the so-called newer arena of development that the country witnesses today. In India, as many as 3.3 million people are suffering from one or the other type of TB and that annually 276,000 lives are lost due to tuberculosis. As many as 9.4 million cases of TB are detected worldwide every year. India accounts for more than one-fifth of the same at about 1.98 million. Two to three per cent of the newly detected cases are also found to be drug-resistant. According to the TB India Report, 40 per cent of the country’s population carries the Mycobacterium tuberculosis in the latent form. These individuals are at risk of developing tuberculosis when bacteria becomes active in the wake of lowered immunity.
It is believed that the incidence of tuberculosis has reduced from 216 per 100,000 per year in 1990 to 176 per 100,000 per year in the year 2012 in India, the tuberculosis mortality per 100,000 population having been reduced from 38 in 1990 to 22 in 2012. In absolute numbers, mortality due to TB has scaled down from 330,000 to 270,000 annually. Now the moot question is whether we have really brought the tuberculosis under control. The answer is in the negative. This is because as soon as the immunity drops, it can lead to the activation of the disease and that we have not been able to bring its determinants under control. Risk factors including biomedical (such as HIV infection, diabetes, tobacco, malnutrition, silicosis, tumor or malignancy etc.), environmental (indoor air pollution, lack of ventilation etc.) or socio-economic (crowding, urbanization, migration, poverty etc.) lead to progression of latent TB to active disease. World Health Organisation (WHO) believes that enough work has not yet been done in India to address the linkage between the prevalence of TB and these risk factors.
Anti-tuberculosis (TB) drug resistance is a major public health problem that threatens progress made in TB care and control worldwide. Drug resistance arises due to improper use of antibiotics in chemotherapy of drug-susceptible TB patients. This improper use is a result of a number of actions including, administration of improper treatment regimens and failure to ensure that patients complete the whole course of treatment. Essentially, drug resistance arises in areas with weak TB control programmes. A patient who develops active disease with a drug-resistant TB strain can transmit this form of TB to other individuals. The treatment of drug resistant tuberculosis is difficult with a prolonged course of large number of TB drugs which are very expansive and have more toxicity. The drug resistant tuberculosis carries a high risk of failure with increased morbidity and mortality.
In a country like ours where tuberculosis is endemic, children catch the infection early in life and develop primary complex. In children younger than three to five years of age, this can spread and lead to severe and serious forms of childhood tuberculosis like tuberculosis of brain, disseminated tuberculosis, miliary tuberculosis, tuberculosis of organs like bones, urinary tract etc. BCG vaccine is given for protection against tuberculosis. It mainly protects from severe forms of childhood tuberculosis. It stands for Bacillus Calmette Gurrain, the strain of bovine tuberculosis is used in the vaccine and attenuated by French scientists, Calmette & Gurrain. BCG is given anytime from birth to 15 days of life. It is to be given to all children as recommended by Govt. of India. BCG, being a live vaccine itself, induces a benign primary complex, which leads to development of some immunity against tuberculosis. Such a child when comes in contact with a patient with tuberculosis can still catch the infection with TB bacteria and develop primary complex, but the spread will be mostly prevented by previous BCG immunity. Hence such children will not develop serious forms of childhood tuberculosis. However, children when they grow as adults can catch tuberculosis again and develop adult form of tuberculosis which is a different type of tuberculosis altogether. Hence BCG vaccination can prevent spread of the primary complex and the severe forms of childhood tuberculosis; but the adult type of tuberculosis is not prevented by BCG. Incidentally BCG also cross protects against leprosy and the efficacy is 20 per cent.
Herd immunity is a form of indirect protection from infectious disease that occurs when a large percentage of a population has become immune to an infection, thereby providing a measure of protection for individuals who are not immune. In a population in which a large number of individuals are immune, chains of infection are likely to be disrupted, which stops or slows the spread of disease. Individual immunity can be gained through recovering from a natural infection or through artificial means such as vaccination. The greater the proportion of individuals in a community who are immune, the smaller the probability that those who are not immune will come into contact with an infectious individual. While herd immunity has helped in eradication and control of small pox and polio, the same is not true for tuberculosis.