Tuberculosis is caused by various strains of mycobacterium, usually Mycobacterium tuberculosis. It usually attacks the lungs but can also affect other parts of the body. It is spread through the air when people who have active MTB infection cough, sneeze, or spit In most cases the disease is asymptomatic, latent infection, and about 10% latent infections eventually progresses to active disease. If untreated, it killed 50% of its victims.
- One third of the world’s population is thought to be infected with M. tuberculosis, and every second a new infection occurs.
- About 80% of the population in many Asian and African countries test positive in tuberculin tests.
- An estimated 1.7 million people died from TB in 2009. The highest number of deaths was in the Africa Region.
HIV and TB
HIV and TB form a lethal combination, each speeding the other’s progress. TB is a leading cause of death among people who are HIV-positive. In Africa, HIV is the single most important factor contributing to the increase in the incidence of TB since 1990.
Drug resistant TB
Until 50 years ago, there were no medicines to cure TB. Now, strains that are resistant to a single drug have been documented in every country surveyed; what is more, strains of TB resistant to all major anti-TB drugs have emerged. Drug-resistant TB is caused by inconsistent or partial treatment, when patients do not take all their medicines regularly for the required period because they start to feel better, because doctors and health workers prescribe the wrong treatment regimens, or because the drug supply is unreliable. A particularly dangerous form of drug-resistant TB is multidrug-resistant TB (MDR-TB), which is defined as the disease caused by TB bacilli resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. Rates of MDR-TB are high in some countries, especially in the former Soviet Union, and threaten TB control efforts.
Stop TB Strategy of WHO
In 2006, WHO had launched the new Stop TB Strategy. The heart of this strategy is DOTS, the TB control approach launched by WHO in 1995. Since its launch, 41 million patients have been treated under DOTS-based services. The new six-point strategy builds on this success, while recognizing the key challenges of TB/HIV and MDR-TB. It also responds to access, equity and quality constraints, and adopts evidence-based innovations in engaging with private health-care providers, empowering affected people and communities, to help strengthen health systems and promote research.
The six components of the Stop TB Strategy are:
- High quality DOTS expansion to even the remotest areas.
- Addressing TB/HIV, MDR-TB and the needs of poor and vulnerable populations.
- National TB control programmes must contribute to overall strategies to advance financing, planning, management, information and supply systems and innovative service delivery scale-up.
- Engage all care providers. TB patients seek care from a wide array of public, private, corporate and voluntary health-care providers. To be able to reach all patients and ensure that they receive high-quality care, all types of health-care providers need to be engaged.
- Empower people with TB, and communities through partnership via Community TB care projects.
- Enable and promote research. While current tools can control TB, improved practices and elimination will depend on new diagnostics, drugs and vaccines.
BCG Vaccine
Tuberculosis was declared a global emergency by the WHO in 1993. Control of this disease relies upon prevention through Bacillus Calmette-Guérin (BCG) vaccination or “preventive therapy” (chemoprophylaxis), and the ascertainment and treatment of cases, in particular employing the “directly observed therapy – short course” (DOTS) approach.
- BCG, or Bacille Calmette-Guérin, used for vaccination of infants in 192 countries. But not widely used in the United States, because TB is uncommon in US. BCG was the first vaccine for TB that was discovered after 1905, when Albert Calmette and Camille Guérin worked at the Institut Pasteur de Lille and the Pasteur Institute in France developing BCG, administering the first human trials in 1921.
- Original BCG vaccine was derived from an isolate of M. bovis at the Institut Pasteur in Lille.
- M bovis ,that has lost its virulence in humans by being specially cultured in an artificial medium for years is still used for producing BCG Vaccine. However, please note that BCG does not always protect against people from getting TB. At best, the BCG vaccine is 80% effective in preventing tuberculosis for a duration of 15 years.
Why BCG shows variable efficacy?
This is the most controversial issue of the BCG administration. It has been shown that the BCG shows variable efficacy, which depends upon geography. The studies have almost concluded that the efficacy of BCG appears to fall the closer one gets to the equator.
Many hypothesis have been postulated so far. One such theory says that in areas where there is high levels of background exposure to tuberculosis, every susceptible individual is already exposed to TB prior to BCG, that is why the natural immunizing effect of background tuberculosis duplicates any benefit of BCG. This means that BCG is less effective in the area where the Mycobacteria is less prevalent. One document of WHO says that in South Africa, the country with the highest prevalence of TB, BCG is given to all children under age three,. but since BCG is less effective in areas where mycobacterium are less prevalent; it is not given to the entire population in these countries. In United States, BCG vaccine is not recommended except for people who meet specific criteria.
Another theory says that Variable efficacy is because of the Genetic variation in BCG strains . In this context, a WHO document says that a so-called RD-2 region, which encodes the mpt-64 gene, is present in the “primitive” BCG strains but is absent from those sub-strains derived from the original BCG Pasteur strain after 1925. However, full details are unavailable.
National Tuberculosis Control Programme
National Tuberculosis Control Programme was started in 1962 on a 50:50 sharing basis between Centre and State. The objectives of the Programme were to reduce the morbidity and mortality; to reduce disease transmission and to diagnose as many cases of tuberculosis as possible and to provide free treatment. The programme was a flop show mainly due to incomplete treatment as treatment completion rate was less than 40 per cent along with some other causes such as inadequate budget; shortage of drugs; emphasis on x-ray diagnosis; poor quality sputum microscopy and multiplicity of treatment regimens.
Revised National TB Control Programme
The National TB Control Programme was later expanded to cover additional 100 million population in 100 districts/reporting units. For the first time in India, a web-based resource centre was developed for preparing TB communication materials. The heart of this programme is DOTS and that is why DOTS is known as the Revised National TB control programme (RNTCP) in India.
DOTS Programme, MDR-TB and XDR-TB
DOTS, is an acronym for Directly Observed Treatment, Short course. The DOTS strategy represents the most important public health breakthrough of the decade, in terms of lives which will be saved. It is based largely on research done in India in the field of TB over the past 35 years. As it is the only strategy effective in controlling TB on a mass basis, nearly 100 countries are following it.
DOTS has five components:
- Government commitment (including both political will at all levels, and establishing a centralized and prioritized system of TB monitoring, recording and training)
- Case detection by sputum smear microscopy
- Standardized treatment regimen directly observed by a healthcare worker or community health worker for at least the first two months
- A regular drug supply
- A standardized recording and reporting system that allows assessment of treatment results
Other Notes
- The technical strategy for DOTS was developed by Dr. Karel Styblo in the 1980s primarily in Tanzania.
- In 1989, the World Health Organization and the World Bank began investigating the potential expansion of this strategy. In July 1990, the World Bank, under Richard Bumgarner’s direction, invited Dr. Styblo and WHO to design a TB control project for China. By the end of 1991, this pilot project was achieving phenomenal results, more than doubling cure rates among TB patients. China soon extended this project to cover half the country.
- In India, Government had adopted the revised strategy for TB in the form of DOTS.
- Since 1993, DOTS has been pilot tested in 20 sites in India as RNTCP.
- In RNTCP the proportion of TB cases confirmed in the laboratory is double that of the previous programme, and the cure rate is nearly triple that of the previous programme. The operational feasibility of DOTS in the Indian context has been demonstrated, with 8 out of 10 patients treated in the programme being cured as compared to three out of 10 under the previous regime.
DOTS has also been shown to prevent the emergence of multi-drug resistant tuberculosis (MDRTB) and to reverse the trend of MDRTB in communities in which it has emerged. Also DOTS can cure TB even in HIV-positive patients. Entire country has been covered under DOTS Strategy by March 2006. The international Joint Monitoring Mission (JMM) in October 2006, has hailed it as the fastest expansion of DOTS in the world.
Isoniazid
Isoniazid / Laniazid or Nydrazid) is the classic antituberculosis medication, first discovered in 1912. It was found to be effective against tuberculosis in 1950s. However, Isoniazid is never used on its own to treat active tuberculosis because resistance quickly develops.
Rifampicin
Rifampicin is a bacteriocidal antibiotic drug. It has been used for TB along with isoniazid, ethambutol, pyrazinamide and streptomycin etc.
MDR-TB
TB that is resistant at least to isoniazid and rifampicin the two most powerful first-line anti-TB drugs is called the Multi-drug-resistant tuberculosis (MDR-TB). It develops because the when the course of antibiotics is interrupted and the levels of drug in the body are insufficient to kill 100% of bacteria. This means that even if the patient forgets to take medicine, there are chances of developing MDR-TB.
MDR-TB is treated with secondline of antituberculosis drugs such as a combination of several medicines called SHREZ
(Streptomycin+isonicotinyl Hydrazine+Rifampicin+Ethambutol+pyraZinamide)+MXF+cycloserine.
XDR-TB
When the rate of multidrug resistance in a particular area becomes very high, the control of tuberculosis becomes very difficult. This gives rise to a more serious problem of extensively drug-resistant tuberculosis (XDR-TB). XDR-TB is caused by strains of the disease resistant to both first- and second-line antibiotics. This confirms the urgent need to strengthen TB control.
Thus, Extensively-drug resistant TB (XDR-TB) is a sub-set of MDR-TB which is further resistant to at least two more drugs which are second line drugs and is thus virtually incurable. XDR TB was first described in March 2006 following a joint survey of laboratories by the WHO, IUATLD, and CDC, Atlanta.