TB can effect any part of the body, though usually targets the lungs as it is the first site of infection and provides a plentiful supply of oxygen. TB kills 2 million people a year, and it is estimated around 30% or the worlds population carry it. Someone is infected by TB every second, and TB is the biggest killer out of all the infectious diseases. Despite advances in TB treatment, the incidence has risen due in MEDCs due to the spread of HIV, more homeless/poor people and a larger elderly population.
Cause
-caused by two types of rod shaped bacteria; microbacterium bovis (m. bovis) and microbacterium tuberculosis (m. tuberculosis).
Symptoms
-initial symptoms include a persistent cough, fatigue, loss of appetite (and therefore weight loss).
-as the disease develops, symptoms include fever and coughing up blood and mucus.
-as the disease develops, symptoms include fever and coughing up blood and mucus.
Transmission
-spreads through the air in droplets of saliva/mucus when an infected person when they sneeze, cough, talk and laugh.
-m. tuberculosis can survive for several weeks after the droplet has dried.
-many TB sufferers are asymptomatic (don't show any symptoms since they have an inactive form). However, it may become active due to malnutrition or another disease, in which case they will show symptoms and become contagious.
When You Are More Likely To Catch TB
-usually, you have to be in close contact with an infected person to catch the disease (unlikely to pick it up from a one off sneezing stranger).
-therefore TB often spreads between family, close friends and work colleagues.
-poorly ventilated and crowded living conditions (e.g. a slum in parts of Asia and Africa).
-if you work or live in a long-term care facility where a relatively large amount of people live together e.g. care homes, nursing homes, prisons and hospitals.
-TB is more common in certain countries, particularly ones in Asia and Africa.
-people with reduced immunity, such as elderly, homeless, malnourished, alcoholics, needle drug users, patients undergoing treatment with immunosuppressant drugs (e.g. after a transplant), those with AIDS and those with a disease that worsens their immune system e.g. diabetes.
-m. bovis can be transmitted from infected cows by drinking their milk so cattle farmers.
-m. tuberculosis can survive for several weeks after the droplet has dried.
-many TB sufferers are asymptomatic (don't show any symptoms since they have an inactive form). However, it may become active due to malnutrition or another disease, in which case they will show symptoms and become contagious.
When You Are More Likely To Catch TB
-usually, you have to be in close contact with an infected person to catch the disease (unlikely to pick it up from a one off sneezing stranger).
-therefore TB often spreads between family, close friends and work colleagues.
-poorly ventilated and crowded living conditions (e.g. a slum in parts of Asia and Africa).
-if you work or live in a long-term care facility where a relatively large amount of people live together e.g. care homes, nursing homes, prisons and hospitals.
-TB is more common in certain countries, particularly ones in Asia and Africa.
-people with reduced immunity, such as elderly, homeless, malnourished, alcoholics, needle drug users, patients undergoing treatment with immunosuppressant drugs (e.g. after a transplant), those with AIDS and those with a disease that worsens their immune system e.g. diabetes.
-m. bovis can be transmitted from infected cows by drinking their milk so cattle farmers.
Course Of Infection
-the bacteria grow and divide in the upper regions of the lung (there is lots of oxygen here).
-the body's immune system responds and white blood cells accumulate at the site of infection in order to engulf and digest the bacteria.
-this leads to inflammation and the enlargement of lymph nodes that drain that part of the lung (primary infection, common in children).
-in a healthy person there are few symptoms and any infection is controlled within a few weeks.
-however, often some bacteria remains, and it may re-emerge to cause a second infection (post-primary tuberculosis, common in adults).
-it occurs in the upper regions of the lung, but this time is hard to control.
-the bacteria destroys lung tissue, resulting in cavities and scar tissue where the lung manages to repair itself.
-a sufferer will cough up damaged lung tissue containing the bacteria (spreads) along with blood.
-without treatment, TB can spread to the rest of the body and be fatal.
-the body's immune system responds and white blood cells accumulate at the site of infection in order to engulf and digest the bacteria.
-this leads to inflammation and the enlargement of lymph nodes that drain that part of the lung (primary infection, common in children).
-in a healthy person there are few symptoms and any infection is controlled within a few weeks.
-however, often some bacteria remains, and it may re-emerge to cause a second infection (post-primary tuberculosis, common in adults).
-it occurs in the upper regions of the lung, but this time is hard to control.
-the bacteria destroys lung tissue, resulting in cavities and scar tissue where the lung manages to repair itself.
-a sufferer will cough up damaged lung tissue containing the bacteria (spreads) along with blood.
-without treatment, TB can spread to the rest of the body and be fatal.
Prevention and Control
-vaccines (an attenuated/weakened version of m. bovis) can be given to those before they catch the disease, and all children in the UK are tested for their immunity.
-giving a vaccine to those who are already immune is unnecessary and dangerous.
-other measures include; better education about TB (especially the need to complete a course of drugs), more/better housing, improved health facilities/treatment and better nutrition/diet to maintain good immune system.
-there are drug treatments but they are expensive, long (6/9 months) and only work on one specific strain of m. tuberculosis (which is always developing).
-giving a vaccine to those who are already immune is unnecessary and dangerous.
-other measures include; better education about TB (especially the need to complete a course of drugs), more/better housing, improved health facilities/treatment and better nutrition/diet to maintain good immune system.
-there are drug treatments but they are expensive, long (6/9 months) and only work on one specific strain of m. tuberculosis (which is always developing).
Questions
1) Which organisms can cause TB? (1 mark)
2) How does TB spread? (2 marks)
3) Why may TB be refereed to as a 'disease of poverty'?
4) Suggest why heating milk at 72 degrees C for 15 seconds (pasteurisation) might help to control the spread of TB. (2 marks)
2) How does TB spread? (2 marks)
3) Why may TB be refereed to as a 'disease of poverty'?
4) Suggest why heating milk at 72 degrees C for 15 seconds (pasteurisation) might help to control the spread of TB. (2 marks)