Tuberculosis

News: Centenary celebration is being observed for the Bacille Calmette-Guérin (BCG) vaccine, which is presently the sole vaccine available for the prevention of Tuberculosis (TB).

Details:

  • TB is caused by a bacterium called Mycobacterium tuberculosis, belonging to the Mycobacteriaceae family consisting of about 200 members.
  • Some of Mycobacteria cause diseases like TB and Leprosy in humans and others infect a wide range of animals. In humans, TB most commonly affects the lungs (pulmonary TB), but it can also affect other organs (extra-pulmonary TB).
  • TB is a very ancient disease and has been documented to have existed in Egypt as early as 3000 BC. TB is a treatable and curable disease. TB is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air.
  • Common symptoms of active lung TB are cough with sputum and blood at times, chest pains, weakness, weight loss, fever and night sweats.

Impact of TB:

  • In 2019, 87% of new TB cases occurred in the 30 high TB burden countries.
  • Eight countries accounted for two thirds of the new TB cases are India, Indonesia, China, Philippines, Pakistan, Nigeria, Bangladesh and South Africa. India reported 1.8 million TB cases between January and December 2020 as compared to 2.4 million the year before.
  • In 2019, MDR-TB remained a public health crisis and a health security threat.
  • MultiDrug Resistant Tuberculosis (MDR-TB) is a strain of TB that cannot be treated with the two most powerful first-line treatment anti-TB drugs. Extensively Drug Resistant Tuberculosis (XDR-TB) is a form of TB caused by bacteria that are resistant to several of the most effective anti-TB drugs.

BCG Vaccine:

  • BCG was developed by two Frenchmen, Albert Calmette and Camille Guerin, by modifying a strain of Mycobacterium bovis (that causes TB in cattle). It was first used in humans in 1921.
  • In India, BCG was first introduced in a limited scale in 1948 and became a part of the National TB Control Programme in 1962. In addition to its primary use as a vaccine against TB, it protects against respiratory and bacterial infections of the newborns, and other mycobacterial diseases like Leprosy and Buruli’s ulcer.
  • It is also used as an immunotherapy agent in cancer of the urinary bladder and malignant melanoma.
  • One intriguing fact about BCG is that it works well in some geographic locations and not so well in others. Generally, the farther a country is from the equator, the higher is the efficiency.
  • It has a high efficacy in the UK, Norway, Sweden and Denmark; and little or no efficacy in countries on or near the equator like India, Kenya and Malawi, where the burden of TB is higher.