Tuberculosis definition and treatment

Tuberculosis, more commonly known by the abbreviation TB, is one of the "emerging diseases". Up until the middle of this century TB was a scourge all over the world. Then, in 1944, with the discovery of the drug streptomycin, it seemed that the White Plague was at last to be conquered. This was not to be so. Over the coming decades the tubercle bacillus developed resistance to each new drug that was added to the fray. Now, at the end of the century, TB has become the biggest infectious killer of youth and adults. In 1997 some 2.9 million TB deaths were reported, and this is certainly an underestimate of the true numbers. One third of the deaths associated with AIDS are due to TB. The scientific name of the tuberculosis germ is Mycobacterium tuberculosis, but it is more commonly known as the tubercle bacillus. It is spread by coughing. The earliest symptoms of active TB are fever, night sweats and weight loss. Later there is cough, and blood may appear in the phlegm. How TB kills It is estimated that up to one third of the world's population may be infected with the tubercule bacillus. Most of these people, however, do not have active TB. Their infection is latent, and may remain so for their whole life, not causing any symptoms. In a proportion of people, however, the infection becomes active and begins to destroy the tissues of the organ it has invaded. Most commonly this is the lungs but TB can also be extrapulmonary, affecting other parts of the body including the spine (in which case it is called Pott's disease), the kidneys, the meninges (which are the membranes covering the brain), and the lymph nodes. In general the infection progresses slowly. If affected persons do not receive treatment, roughly one third of those with active TB die within two years and another third within five years. The epidemiological significance of this long period between onset of symptoms and death is that during all this time the affected person is coughing and spreading the TB bacillus to others in his or her entourage. The World Health Organisation (WHO) estimates that one person becomes infected with TB every second. The TB bacillus causes a process called caseation, a word derived from the Latin for cheese. The slowly progressive inflammation of TB destroys the tissues and leaves in their place a thick cheesy substance. Especially if more than one organ is affected this leads the person to lose weight in a dramatic fashion, almost as if they are being consumed by the disease. This, indeed, gave TB its common name during the 19th century, consumption. The final cause of death may be either multiple organ failure or internal haemorrhage (bleeding) in the lungs, which may happen when the advancing destruction erodes into an artery. Managing the epidemic of TB The first priority in managing the current upsurge of TB is to ensure that there are health services in place that are sustainable long term. It can be argued that starting a TB control programme that fails after a certain period is worse than never having started one at all, because a failed programme leaves as its legacy patients with drug-resistant bacilli. For example, MSF sometimes chooses not to start TB treatment in an unstable refugee situation, where it is likely that the population will move and be lost to follow-up. What we do instead is plan and wait until the situation stabilises. DOTS - or directly observed treatment, short course - has been adopted by the World Health Organisation as a global strategy. According to previous strategies, patients were given a week or even a month's supply of TB medicines and told to come back at the end of that period for more. Often they did not take the medicines, and often they did not return. With the DOTS strategy, however, health workers are required to give each patient only their daily dose of medication and watch while they actually swallow it. They must also monitor progress until the treatment course is finished and the patient is free of tubercle bacilli. Curing the disease is thus the responsibility of the health worker, not the patient. WHO has set a goal for TB control programmes to cure 85 per cent of detected new active TB cases and detect 70 percent of estimated cases. DOTS is likely to be the only strategy to have any hope of achieving these targets. Preventing TB MSF teams approach the prevention of TB in several ways.
  • detection and treatment of active cases (This is essential, as these people are spreading the bacillus to others. Paradoxically, in the early stages of a TB project we may not go out actively seeking cases - rather, during the first months we concentrate on training the local national health workers to handle according to the DOTS strategy the cases that come to the clinics of their own accord. To go out finding too many new cases too quickly risks overwhelming the health services and compromising quality of care and supervision.);
  • setting up laboratory facilities in district hospitals so as to allow adequate diagnosis of TB;
  • education of the population and of community health workers on the symptoms and signs of TB, so that affected people come forward to be treated once the programme is set up and running;
  • advocacy in refugee situations for adequate shelter and living space, since crowded conditions favour contagion;
  • setting up of control programmes among disadvantaged groups such as prisoners, slum dwellers and street people, who would not otherwise have access to care. An example - DOTS in action in Siberia. In Russia the prevalence of TB is high and still rising, and Siberia is the region that is most severely affected. The prevalence there is double the rate in the rest of country. This is due in part to the inadequacies of the Siberian prison system. More than one million prisoners are housed in conditions so crowded that the transmission of an airborne disease like TB is almost unavoidable. The MSF teams work in the prisons of Mariinsk and Novokuzniets. The hospital prisons there were heavily overburdened with patients and ill-equipped to deal with a complex condition such as TB. We set up the DOTS strategy and trained the prison medical staff. Patients with active smear-positive TB are targeted as they are the ones who are contagious. Advocacy is an important element of this project in order to raise public awareness about the prison TB epidemic and its consequences for the country as a whole. MSF is working with the local authorities to ensure that the epidemic is managed. How MSF teams treat TB patients TB is difficult to treat. There is no single antibiotic that is capable of killing all the tubercle bacilli in a person's body. Apart from being hardy, TB germs can also develop resistance to drugs used against it. The only effective method is to use several different drugs combined together over a long period of time - usually a minimum of six months. This presents the further difficulty of ensuring that patients actually take all of their medicines over that long period of time. After a few weeks they will usually start to feel better - the fevers and haemoptysis may recede, and they begin to gain weight. The danger is that they will then cease taking the medications. If that happens, the patients will eventually relapse and, what is even more serious, the tubercle bacilli that have been thus exposed to a sub-lethal dose of drugs have the opportunity to develop resistance to those drugs. Once the patients start coughing again they will spread these resistant organisms to others. MSF had good results treating TB in the Indochinese refugee camps in Thailand during the 1980s. The strategy we used there was to train community health workers from among the refugees to supervise the therapy of the TB patients on a day-to-day basis. This experience and others elsewhere were the forerunners of a strategy known as DOTS - which stands for Directly Observed Treatment, Short-course. This strategy is discussed in the section on managing the epidemic. MSF has TB control projects in countries as diverse as Angola, Guinea, Russia, Kazakhstan and Cambodia. The drugs that we commonly use in these programmes include isoniazid, streptomycin, ethambutol, pyrazinamide and rifampicin. These medicines are usually referred to by their abbreviations: INH, SM, ETH, PZA and RIF. The commonest regimen used under DOTS is two months of daily doses of INH, RIF, PZA and EMB followed by four months of twice weekly INH and RIF. This regimen is expensive but is usually highly effective.