Battling tuberculosis on many levels

(First of two parts)

The problem with tuberculosis is that you may already have it. Unknowingly, you may be harboring inside your body the agent that causes it, as you go about your daily routine. Imagine it quietly waiting inside your body, patiently biding its time until it finds an opportunity to catch you when you are unaware – and when you are weakest. Do we need any more reason to learn more about it?

Everyone has heard of TB. Quite possibly, you may know someone who has it. It is an ancient, highly infectious, and persistent disease that has plagued humans for centuries. Despite the availability of a vaccine and anti-TB drugs, it remains the leading infectious disease worldwide, especially in developing countries. It is responsible for killing more humans than AIDS, malaria, leprosy, and diarrhea. In 2000, the World Health Organization (WHO) estimated that there were 249,655 new cases of TB in the Philippines. An even scarier statistic is that more than a fourth of that number is projected to die. Also in the same year, it was reported that the Philippines had the seventh highest incidence in the world and the second highest in Asia. Because of these astounding figures, the Philippine government has vigorously renewed its commitment to fight the deadly disease.

TB is most often caused by the bacterium Mycobacterium tuberculosis. It is an immobile, rod-shaped bacterium which requires sufficient levels of oxygen to survive. This is why M. tuberculosis complexes are almost always found in the well-aerated upper lobes of the lungs. The bacterium is an intracellular parasite of macrophages, a kind of blood cell that functions in ingesting and destroying large amounts of foreign material. Unfortunately, humans are the primary host and the only real or natural host of M. tuberculosis. When talking, spitting, or coughing, a person with TB releases tiny, aerosolized droplets contaminated with the bacteria. An unsuspecting, healthy individual may inhale the expelled bacteria and contract the infection (luckily, one is unlikely to become infected by just one exposure). The microbes are engulfed by macrophages present in the alveoli, and they replicate in these cells for two to three days before spreading throughout the body.

TB does not immediately manifest itself upon infection. The disease has two stages, the first one being latent infection. It is characterized by the formation of hard, grayish nodules, called tubercles, in the lungs. But for most infected people, the macrophages are able to contain the bacteria for life. (Inside the macrophages, the bacteria are not destroyed but continue to live in a dormant, spore-like state.) No apparent disease is noted; they suffer no effects and are not contagious. Since this stage is asymptomatic, no one suspects the presence of the microbe in the body. It is estimated that a whopping two billion people – one-third of the world’s population – is currently in this state.

However, in 10 percent of cases, the disease progresses into the second stage of active tuberculosis. Factors such as old age, malnutrition, or the presence of another disease – especially HIV/AIDS – enable latent infections to develop into active TB. In this stage, tubercles proceed to the air passages, blood vessels, and other parts of the body. Local tissue and cells of our immune system die, causing the formation of granulomas, sites where active microbes can survive. These granulomas expand with more destroyed lung tissue and may spread into the larger airways of the lungs. They may also liquefy as the disease worsens, allowing the bacteria to multiply and spread to create new lesions. Meanwhile, the patient experiences a plethora of symptoms, from chest pains and shortness of breath to weight loss, from fatigue and paleness to painful joints and swollen glands. TB during this stage becomes very contagious.

To address the TB problem on a worldwide scale, the Global Tuberculosis Programme of the WHO developed DOTS (Directly Observed Treatment, Short-course) in 1993. More than just prescribing drugs and ensuring that their supply is uninterrupted, DOTS underscores the importance of self-reporting to health centers and of patient compliance to the treatment. Most importantly, it enjoins governments worldwide to go all out in the fight against TB. In this program, there is a standardized recording and reporting process that allows assessment of treatment results for each patient and of the overall TB control program. With DOTS, the patient, health care workers, public health officials, governments and communities all share the responsibility of effectively treating and controlling the killer disease.

(To be concluded)

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John Phillip L. Fadul completed his B.S. MBB degree at the National Institute of Molecular Biology and Biology in UP Diliman in 2004. He is presently taking his Master’s at the same institute. He works at the UP Marine Science Institute, where he tests marine compounds for cytotoxicity to mammalian cells. E-mail him at [email protected].