Tuberculosis
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What is Tuberculosis?
Tuberculosis (TB) is an infection. It is mostly caused by a germ called Mycobacterium Tuberculosis (often abbreviated to M. Tuberculosis). A second germ in the same family, M. Bovis, now rarely causes disease in the UK. M. Tuberculosis, together with M. Bovis, world-wide, it is the commonest infectious disease. There are about 8 million new case of TB per year and about 3 million die from it (mostly in the third world).
There are many other germs in the mycobacterium family (the Mycobacteria). These are known as Atypical Mycobacteria. Some of them are completely harmless and can be found in soil or some water supplies. Others are usually harmless, but can cause serious disease in patients whose immune system is not working properly. This disease is then know as Atypical Tuberculosis.
How do people catch TB?
You get infected with M.Bovis from unpasteurised milk or contact with infected cattle. M. tuberculosis is spread by coughing. You have to be in close contact with a patient with TB for some time before you are likely to catch it from them. Only patients who are coughing up large numbers of TB germs (sometimes known as Open TB) are infectious. If you live with someone who has open TB and are particularly if you are not protected by aBCG vaccination, your risk of catching TB is high.
I thought TB was a rare disease now. How common is it in the UK?
At the beginning of the 20th century a quarter of all deaths were due to TB. It became much less common as people were better fed with better housing. This was happening even before antibiotics started to be available in the late 1940's. In the late 1970's some doctors were predicting that there would be no TB by the millennium. In the early 1980's however, rates started to climb again. The rate is steady now, but is still about 11 new patients per 100,000 population per year.
Why is it more common again?
There are many reasons. There is much more travel, particularly air travel, so people get infected in third world countries and bring it back to the UK. (TB has a long incubation period, so people infected abroad may not obviously be ill when they arrive). TB can affect healthy people but usually affects people whose immune system is weak. This includes elderly people, diabetics, alcoholics, people on immune suppressing drugs like steroids, and people with AIDS. All of these risk factors have become more common. Because some countries have been slack about making sure patients are treated properly there is more resistant TB. Patients who refuse to take treatment or stop taking it spread TB to others.
What types of illness does TB cause?
TB can affect any organ in the body. Most commonly, however, it affects the lungs.
In pulmonary (lung) TB the TB germ is inhaled into the lungs and cause infection there. If a patient has a very healthy immune system and the number of germs getting into the lungs is fairly small, they may be able to stop the infection spreading and it will be contained in a scar in the lung (called a Ghon focus). This is known as Primary tuberculosis. The patient will develop immunity to TB and their Heaf Test will become positive. The scar will be visible for the rest of their life on their chest X-ray (known as a primary complex) but there will be no symptoms. Primary TB is very common in older people in the UK. They will have been infected as children or young adults. These people are often surprised to be told by their doctors that they have had TB.
There is one type of primary TB, however, which is very dangerous. This is called milliary TB. In this condition the primary infection gets straight into the blood stream and affects the whole body. The nervous system is frequently affected with meningitis and or encephalitis.
If a patient gets a more severe infection initially, or if primary disease becomes active again, post primary TB will develop. In the lungs a pneumonia develops which will cause permanent damage if not treated promptly. TB characteristically produces cavities (holes) in the lung. The main symptoms are a cough, usually with sputum which is yellow or green. Coughing up blood is quite common. If damage to the lung is severe, patients will become breathless. Patients usually have a high fever and sweats at night. Weight loss, poor appetite, weakness and tiredness are common. However some patients may have no symptoms at all.
Any part of the body can be affected by TB if it gets from the lungs into the blood stream and there may be no obvious disease in the lungs. Symptoms like fever and weight loss are often seen. Other symptoms will depend on which part of the body is being affected.
It can spread to the membranes lining the lung (the pleura) and cause inflammation which leads to fluid collecting around the lung (a pleural effusion). The fluid will gradually squash the lung, causing breathlessness.
After the lungs, the lymph glands are most commonly affected. (Asian people are particularly likely to get glandular TB whereas Caucasians are more likely to get pulmonary TB). The main symptom is enlarged lymph glands, usually in the neck or armpits. Often these are not painful. However they may get larger and sometimes the infection in them will escape onto the surface of the skin through a sinus (a hole in the skin, leading down to the infected lymph gland) from which pus may leak. Sometimes only lymph glands inside the chest are affected and this may only be seen on a chest X-ray.
TB can affect the nervous system, often as a result of miliary TB. It causes meningitis (infection of the membranes and fluid around the spinal cord) or encephalitis (infection of the membranes and fluid around the brain). Symptoms are similar to other types of meningitis with headache, drowsiness and neck-stiffness but develop more slowly. Young children are particularly at risk if they are in contact with an infectious adult.
TB of the bones particularly affects the spine but any bone can be involved. This may cause local pain. In advanced cases a bone may collapse. In the spine this can press on the spinal cord and cause paralysis.
Many other organs can be affected by TB. These include pericardial effusion (inflammation around the heart), tuberculous peritonitis (inflammation in the abdomen), urinary tract TB (affecting the kidneys or bladder), rare types of skin disease, and pelvic inflammatory disease (infertility).
How is TB diagnosed?
It is suspected from typical symptoms as above. There may have been contact with another patient with TB. There may be abnormal findings on examination. However sometimes there won't be anything for the doctor to find. In many patients the diagnosis comes from the GP requesting a chest X-ray.
Patients are asked to cough up sputum samples. (In patients who can't cough up sputum, a bronchoscopy is often done to obtain a sample from the affected part of the lung). In a heavy infection the laboratory can see TB germs with a rapid staining test and confirm the diagnosis within a day or two. In less severe infections, however, the germ has to be grown in the laboratory. This is a slow process and usually takes up to 2 months. (There are other more rapid diagnostic tests e.g. the "PCR" test, but these are expensive and only done when it is very important to have a quick diagnosis).
In other types of TB a sample is obtained, whenever possible, from the affected organ (e.g. in lymph node TB a sample of pus from a sinus can be sent or a minor operation done to remove one of the lymph glands for the pathologist to examine it).
The Heaf Test or Mantoux test will usually be positive. However, some patients with severe TB can have negative results and these tests are less helpful in people who have been exposed to TB before or have had a BCG vaccination.
Because of the time it can take the laboratory to grow the TB germ, many patients are started on treatment for TB before the diagnosis is proved (to prevent the risk of further harm to them or risk them giving TB to other people). Sometimes the diagnosis is never proved but a full course of treatment is still given until the patient gets better, unless another cause is found.
How is TB treated?
The Mycobacteria germs are very sophisticated and it is difficult to kill them with antibiotics. When the TB germ is in an active phase antibiotics can kill it quite quickly. Most patients with open TB will therefore become much less infectious within a few weeks of treatment. However, it then goes into a dormant or hibernating phase when it is difficult to kill so treatment has to go on for a long time. The first successful forms of antibiotic treatment (known as chemotherapy) used to take 2 years. Even with modern treatment this has to be given for 6 months.
The TB germ easily becomes resistant to antibiotics. This is prevented by using several antibiotics at once. Around the world there are now many varieties that are resistant to some antibiotics. Most dangerous, but fortunately still rare in the UK, is multiple drug resistant TB (MDRTB).
Standard treatment in the UK involves 2 months treatment with 4 drugs (Rifampacin, Isoniazid, Pyrazinamide and ethambutol; although ethambutol may not be needed for some patients). Provided there is no evidence of a resistant infection, there is then a further 4 months treatment with Rifampacin and Isoniazid. Occasionally treatment for longer than 6 months is needed. To make it easier to take lots of different antibiotics, they are usually given as combined medicines with trade names like Rifater, Rimactazid and Rifinah.
How safe is treatment?
It is very safe. The risk of serious side effects with hepatitis (inflammation of the liver and jaundice) or eye damage (possible with ethambutol only) is about 1/1000 patients. Provided treatment is promptly stopped the risk of permanent damage is even smaller. (Patients who are frightened of taking these drugs should remember that these are very small risks. Not taking treatment however, carries a very high risk of permanent disability or even death, plus the risk of giving TB to other people).
Patients who have resistant TB or who get side effects need treatment with other, so called, second line antibiotics. This may include streptomycin which has to be given by injections. Second line treatment may cause more side effects, and usually means longer courses of treatment, but still has a very good safety record.
What do I need to know about taking drugs for TB?
You must take them every day for as long as your doctor tells you. It is very important not to stop them just because you feel better; otherwise the TB will come back again. Next time it may be resistant and need more complicated treatment as well as doing you more damage. Make sure you take all your antibiotics together. Only taking some of them is likely to make your TB resistant.
Antibiotics for TB can interfere with some other medicines. Make sure the doctor treating you knows about all other medicines you take. Some of these might have to be changed, but any other conditions you have can still be treated properly. Women taking the contraceptive pill should use an alternative contraceptive method.
The medicines will make your urine go an orange colour. This is harmless and will go back to normal when treatment has finished. Blowing your nose or tears may also look orange. Get advice from your doctor immediately if you think you have jaundice or if your vision is deteriorating (colours may look strange).
What is a Heaf test or Mantoux test?
These are tests for immunity to TB. An extract of dead TB material is injected into the skin of the forearm. The Mantoux test involves an injection with a single needle into the skin. The size of any lump which comes up in the next 2-3 days shows how good the immunity is. The Heaf "gun" uses six tiny needles in a ring. This is read after a week and if slightly positive comes up as a ring or as a lump if strongly positive.
One of these tests is used before giving a BCG vaccination. If the test is positive there is no need for BCG because the patient has immunity already. Giving a BCG would also risk causing a very bad reaction in the skin.
What is BCG vaccination?
BCG stands for "Bacille Calmette Guerain" named after the doctors who developed it. It is a live organism developed from the mycobacterium family, but it is harmless. It is injected into the skin of the shoulder. Over about six weeks it produces a local infection which heals as a scar. This stimulates the immune system and gives protection against TB. For most people, provided a scar forms, immunity lasts for very many years.
Do I need BCG Vaccination?
In all parts of the UK it is recommended for babies of Asian parents and some other races (because these people are naturally more susceptible to TB). It is also given to children who are in contact with parents who have TB, if their Heaf test is negative.
Most Health Authorities provide BCG vaccination at school at about age 14. A few stopped doing this in the early 1980's because of low rates of TB in their area. It is quite likely that even these Health Authorities will bring it back again.
Young adults who haven't had BCG are given it if they go into occupations at high risk, e.g. nursing and medical students. Anyone spending more than a few weeks in a third world country should also consider it.
How effective is it?
In the UK BCG vaccination gives about a 70% protection against TB. The brands used in some other countries are less good. It is most valuable in protecting children (because they catch TB more easily than adults). The greatest value of BCG vaccination is that it helps protect children from miliary TB and TB meningitis.
Why do I need to go to the Contact Tracing Clinic?
Tuberculosis is covered by the Infectious Diseases Act. If a doctor diagnoses active TB they are legally obliged to fill in a report form. This goes to the local Health Authority. Their Health Visitor interviews the patient and decides if they are likely to be infectious. If so, she finds out who they have been in contact with and decides which of these people are likely to be at risk of having been infected. They are then sent an appointment to go to their local chest clinic.
Depending on their age, people called to a contact clinic will have either a Heaf or Mantoux test and a maybe a chest X-ray. (Most people will not be examined but occasionally this will be necessary so you should not be alarmed if the doctor wants to examine you as well). What the doctor in the contact clinic will then chose to do depends on results of these tests and is far too complicated to explain here. However, he or she will tell you what you need. Some people may not need any further follow up, some will be advised to have a BCG vaccination and some will be asked to have further follow up with chest X-rays over the next year or even longer.
A few patients who have obviously developed TB will be put on a full course of treatment for 6 months. Other people with evidence of a very early infection (a strongly positive Heaf/Mantoux test but normal x-ray) will be given a limited course of antibiotics called chemoprophyllaxis; either Rifampacin plus Isoniazid for 3 months or Isoniazid alone for 6 months. Chemoprophyllaxis may be needed in very young children. This is quite safe and can be given in syrup form. You should not be surprised if different members of the same family or different people in the same work group are not all treated the same way
Atypical TB
Atypical TB almost always occurs in people who either have an immune defect (e.g. AIDS, treatment with steroids or other immune suppressant drugs) or have previous long-standing damage to their lungs. They are not infectious to other people so contact tracing is not usually required once it is known that they have atypical and not ordinary pulmonary TB. Atypical TB is much more resistant to treatment and long courses of antibiotic treatment, (sometimes up to 2 years) are needed. Some patients relapse after treatment is stopped and may need even more treatment.
How can we get rid of TB?
TB is curable. We could get rid of it in the UK if we tackled the two main problems:-
1. Prejudice- Racial prejudice, and the idea that TB is a "dirty" disease, make people "ashamed" of having it and less willing to come forward to be diagnosed and treated. It is very important that attitudes change and that there is more openness about the diagnosis. It is also very important that everyone who is asked to go to a contact tracing clinic does so.
2. Patients must co-operate with treatment - There is research going on which may eventually mean that TB could be cured very quickly but, until then, every patient with TB has a responsibility to everyone else to make sure that they take their treatment properly so they are cured themselves and don't give TB to others.
For further information, please contact TB Alert
Web Links and Links to Other Information
Please note that the Society does not endorse the content of any of these web links, but hopes that by providing the links below it is providing a useful service to the respiratory community.
European TB programme (linked to WHO)
Surveillance of tuberculosis in Europe.
http://www.eurotb.org/
IUATLD
The IUATLD has as its mission the prevention and control of tuberculosis and lung disease, as well as related health problems, on a world wide basis, with a particular emphasis on low income countries.
http://www.iuatld.org/
TB Alert
TB Alert was set up by people who felt that with its long tradition of TB work, there should be a greater response in Britain to the resurgent threat of tuberculosis - already declared a global emergency by the World Health Organisation (WHO) in 1993.
http://www.tbalert.org/
WHO Global TB Program
http://www.who.int/gtb/