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Tuberculosis: The science of tuberculosis

The "rest cure" – an extended stay in a sanatorium, or TB hospital, away from home and family – was the only hope for tuberculosis patients in the first half of the 20th century. Then came a cure for the dreaded lung disease: powerful antibiotics that made the sanatorium a thing of the past. But TB was far from eradicated, and new drug-resistant strains surfaced in the 1980s, threatening vulnerable groups such as the urban poor and northern aboriginals. Now, over half of new TB cases in Canada are found in newcomers, and Canadian scientists are at the forefront of new treatments for the disease.

It spreads through the air like a cold virus, but it usually takes multiple exposures for a person to catch tuberculosis. Some people harbour the bacterium harmlessly for years before contracting active TB, which destroys the lungs and slowly eats away at the body. A scientist interviewed on the CBC radio program Quirks & Quarks says the key to eliminating TB is treating people before they become infectious. 
• The tubercule bacillus, the bacteria that causes tuberculosis, was discovered by German scientist Robert Koch in 1882. Before Koch's discovery, TB was thought to be hereditary or to afflict mainly people of a sensitive, artistic temperament.
• The bacterium, called Mycobacterium tuberculosis, enters the body one of three ways: by inhalation, ingestion or inoculation. Butchers and other people working with animals were the most likely to contract the bacteria by inoculation.

• Once the bacteria enter the body, a tubercle, or tube-shaped lesion, develops at the point of entry or in the lung. If a person is healthy, the body's defences attack the tubercle so that it hardens into scar tissue and seals in the bacteria. The disease is then dormant and non-infectious.
• Tuberculosis takes its name from these tubercles; a person with the disease may be said to be tuberculous.

• Should a person's immune system weaken due to other diseases, malnutrition, or old age, the tubercles will grow and multiply, spreading the bacteria. The tubercles become cavities in the lung which expel pus, and the patient coughs up this pus, often mixed with blood. Eventually the cavities consume the lungs.
• The coughed-up material is called sputum. A sputum test is the most common means by which doctors make a diagnosis of active tuberculosis.

• TB doesn't just attack the lungs. The bacteria can also take hold in the lymph nodes, kidneys, bones, joints, larynx and central nervous system.
• Anyone can be infected by TB but the disease develops more frequently in infants, adolescents, young adults and those with weakened immune systems.
• Symptoms of TB include a chronic cough, fevers, weight loss, night sweats, constant tiredness, and loss of appetite.

• The Tuberculin Skin Test is used to detect TB infection in healthy people. A dose of tuberculin is injected under the skin of the forearm. A mark called a wheal develops at the site of the injection, and is measured after 48 to 72 hours. If it's over 10 millimetres across, the test is positive, meaning the person has come into contact with TB bacteria. Further testing, like a chest X-ray or sputum test, is needed before a person is diagnosed with active TB.

• Before the routine pasteurization of milk in Canada, it was possible to contract bovine tuberculosis by drinking cows' milk. This type of TB attacks not the lungs but the glands, bones and joints, and was often the cause of death in children under age five.
• Pasteurization involves heating milk to kill any bacteria present and discourage further growth.
• Toronto passed a law in 1918 requiring that cow's milk for sale be pasteurized; Ontario followed suit in 1938.
Medium: Radio
Program: Quirks & Quarks
Broadcast Date: Dec. 14, 1996
Guest(s): Dr. Don Enarson
Host: Bob McDonald
Duration: 15:12

Last updated: August 21, 2013

Page consulted on February 20, 2014

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