What is tuberculosis?

Tuberculosis (TB) is a bacterial infection resulting from a complication of pneumonia. It is often regarded as a form of pneumonia.

It is also considered to be a multisystem disease because other than the lungs, which are the most commonly affected organs, tuberculosis can affect any other part of the body except the teeth, nails and hair.

It is common in the developing countries due to HIV, poverty, wars and malnutrition among many other factors.

It has recently declined in occurrence though it is still a major source of concern on global health.

And what causes tuberculosis?

The causative agent of tuberculosis is an aerobic bacterium known as Mycobacterium tuberculosis. Because it is aerobic, this organism survives best in a place richly supplied with oxygen, like the lungs. It is found in various strains but M.tuberculosis hominis, M.tuberculosis bovis and M.tuberculosis africanum are the most common. The reservoir of M.bovis is cattle whereas the reservoir of M.africanum is human.

Other strains include: M.microti, M.pinnipedii and M.canetti.

What about the mode of transmission for tuberculosis?

The transmission of M.tuberculosis occurs via:

  1. Inhalation of droplet containing the tubercle from other infected persons. This usually transmits the M.tuberculosis.
  2. Drinking of non-sterilized milk from infected cows.

And how about its pathogenesis?

When the organism is inhaled, it reaches the alveoli of the lungs and initiates a cell-mediated immune response. The organism is phagocytosed by microphages and together, they form a complex which is hardened through the process of calcification.

What are the types of Tuberculosis?

Tuberculosis can be classified according to the time of infection whether first time or second time. They are as indicated below:

  1. Primary tuberculosis. This is a Tuberculosis infection occurring for the first time. It can stay dormant or progress to cause a disease.
  2. Secondary tuberculosis. This can either be activation of primary infection or second time infection to a person who had recovered from TB.

Tuberculosis can also be classified on the basis of its site of infection and this includes:

  1. Pulmonary TB which is only confined to lungs.
  2. Extra-pulmonary TB which affects other tissues or organs as well.
  3. Milliary TB which means disseminated TB. It has been dispersed to many other organs of the human body.

What are the risk factors for tuberculosis?

There are a number of factors that put you at an increased risk of contracting tuberculosis. They include:

  1. Extremes of ages. Tuberculosis mostly affects children and the elderly. You adults are also commonly affected.
  2. Overcrowding. With these, the chances of inhaling a droplet containing the tubercle are more high because of the closeness. Prison and congested matatu vehicles are an example of common places where people overcrowd.
  3. Smoking cigarettes.
  4. Contact with pulmonary tuberculosis patient. You will easily inahle the tubercle.
  5. Deficiency of vitamin D and A.
  6. A previous infection with Mycobacterium tuberculosis.
  7. Diabetes mellitus.

What are the signs and symptoms do tuberculosis?

  1. Fever
  2. Drenching night sweats
  3. Weight loss
  4. Cough often with haemoptysis
  5. Dyspnoea
  6. Orthopnea
  7. Unresolving pneumonia
  8. Loss of appetite
  9. Pleural effusion

How is tuberculosis transmitted?

  1. Inhalation of droplets containing tuberculosis causing organisms.
  2. Drinking milk from a cow infected with tuberculosis. This transmits M.bovis.

How does tuberculosis spread within your body?

Once in the human body, the disease can spread through routes such as:

  1. Local spread - carriage of the tubercle bacilli by macrophages into the surrounding tissues.
  2. Lymphatic spread - This is how TB lymphadenitis occurs. The tubercle passes into the lymph nodes through the lymphatic spread.
  3. Hematogenous spread - the lymphatic system usually drains into the venous system. The bacilli from the lymphatic system may therefore enter the veins and be transmitted to other parts of the body through the blood.
  4. Natural passages such as infected Sputum into larynx, renal lesions into ureter and down into the bladder, e.tc.

How is the diagnosis of tuberculosis done?

Active tuberculosis infection can be detected through various labaratory investigations such as:

  1. Microscopy
  2. Gene expert
  3. Z-N stain
  4. Culture on special media
  5. Sputum culture on L-J media

Chest X-ray, complete blood count and histopathology are also done to confirm and determine the type of TB.

Latent infection is diagnosed through:

  1. Tuberculin skin test and
  2. Interferon Gamma test.

What is the treatment of tuberculosis?

All forms of tuberculosis are usually treated for 6 months except tuberculosis of Milliary tuberculosis and tuberculosis of bone and joint which is treated for 12 months. Treatment is done in two phases.

The first phase is the intensive phase where rifampicin, isoniazid, pyrazineamide and ethambutol are combined for the treatment of tuberculosis. It is usually done for 2 months and is designed to rapidly decrease the overall number of tuberculisis bacteria in the body.

The second phase is the continuation phase where only two of the drugs, rifampicin and isoniazid are continued. It takes place for the next 4 months and is aimed at clearing the remaining bacteria.

For the milliary tuberculosis and tuberculosis of bone and joint, the continuation phase takes 10 months.

Resistant strains have, however, emerged and in this case second-line drugs anti-bacterial drugs should be considered. These include flouroquinolones, macrolide, amikacin, cycloserine, capreomycin and kanamycin.

Non-compliant patients should be directly observed to ensure that they take the right drugs at the right amounts and at the right time.

Any person having an active tuberculosis and is not treated is infectious and can transmit the disease to another person. But once the person has commenced on drugs, he/she no longer becomes infectious.

How can tuberculosis be prevented?

Prevention measures for TB may include the following:

  1. Vaccination. Children are usually vaccinated with BCG vaccine.
  2. Avoiding overcrowded areas, for example congested public vehicles such as matatus.
  3. Ensuring proper hygienic measures.
  4. Improvement of living standards for example through proper housing and nutrition.
  5. Use of isonaizid preventative therapy for those who are suspected to have contracted tuberculosis.
  6. Detection and effective treatment of latent tuberculosis.
  7. Milk pasteurization and destruction of tuberculosis infected cattle to prevent transmission of M.bovis to humans.
  8. Directly observed therapy for non-compliant patients.

What is the prognosis of tuberculosis?

The outcomes of tuberculosis are good with treatment and bad without treatment. Twenty-five percent of those who do not get treated usually die in the first year. Known cases of tuberculosis should therefore be treated with adequate therapy.

Sometimes back, in some countries, infected people who failed to adhere to the TB drug regimen used to be imprisoned until they finished taking the drugs. Nowadays, this has been abolished because it has been seen as a violation of the human rights.

Tuberculosis is a public health concern. Any hospital which registers a case of tuberculosis is expected to report to the ministry of health for record keeping.