Fight Against Tuberculosis

by Senthamaraiselvan Pooja – Art in Tanzania internship

Background of Tuberculosis

Tuberculosis (TB) is an airborne infectious disease caused by a bacterium called Mycobacterium tuberculosis. The United Republic of Tanzania is one of the 30 countries with the highest burden of TB in the world. According to WHO, 142 000 people (253 per 100 000 population) fell ill with TB in 2018 [1].

A large proportion of persons with the illness (90% to 95%) have latent TB infection (LTBI) in which case they do not exhibit any symptoms as the immune system will contain and control the infection. However, the infection typically does not get eliminated and most people with LTBI do not know that they are infected because they do not feel sick.

The bacteria can remain inactive for many years and the chance of developing active TB decreases over time [2].

Approximately 5% to 10% of individuals are not able to control the initial infection and will develop primary tuberculosis. The dormant bacteria can also become active again in a few of those with LTBI due to various factors that compromise the immune system. Active tuberculosis among this group is referred to as reactivation tuberculosis [3].



Main Differences between Latent and Active TB
Latent TB
●                     TB bacteria are “asleep” in your body
●                     You do not have symptoms and you feel well
●                     You cannot pass TB on to others
●                     It can only be detected through a blood test or TB skin test
 
Active TB
●                     TB bacteria are “awake” and making you ill
●                     You will have symptoms that make you feel unwell
●                     You can pass TB to others if it is in your lungs
●                     It shows up on a chest x-ray if you have TB in the lungs [4]
 
Symptoms of Active TB
Tuberculosis most often affects the lungs and respiratory tract. This is known as pulmonary TB. However, TB can affect almost any organ system. Active tuberculosis can manifest as pulmonary or extrapulmonary disease irrespective of whether the individual is a primary or reactivation case. However, approximately 80% of clinically manifested tuberculosis is pulmonary among individuals with good immune function, while extrapulmonary tuberculosis can be seen more frequently in immunocompromised people.
 
Pulmonary TB can be mild or severe and present with any of the following symptoms: excessive coughing (sometimes with blood in the sputum), chest pain, general weakness, lack of appetite, weight loss, swollen lymph glands, fever, night sweats, chills, and fatigue. Extrapulmonary TB can also present with fever, fatigue, night sweats, and progressive weakness, but prominent symptoms will typically stem from the affected organ system.
 
Extrapulmonary TB commonly involve the pericardium (thin sac surrounding the heart), lymph nodes (small, oval-shaped cluster of immune cells located throughout the body), urogenital area, gastrointestinal tract, central nervous system, adrenal glands, bones, eyes, and skin [3]. If untreated, active TB can be life-threatening.

TB Transmission

TB is spread to susceptible individuals when they breathe in contaminated droplets that are released into the air when an infected person (with Active Tuberculosis) nearby sneezes, coughs, talks or laughs. Humans can also get ill with TB by ingesting unpasteurized milk products contaminated with Mycobacterium bovis, also known as Bovine Tuberculosis [2].

Risk Factors for Progression and Development of Active TB Disease

In general, people at high risk for developing active TB once infected with M. tuberculosis include:

  • People living with HIV/AIDS
  • Children younger than 5 years of age
  • Persons who are receiving immunosuppressive therapy
  • Persons who were recently infected with M. tuberculosis (within the past 2 years)
  • Persons with a history of untreated or inadequately treated TB disease
  • Persons with silicosis, diabetes, chronic renal failure, leukemia, lymphoma, or cancer of the head, neck, or lung
  • Persons who have had a gastrectomy or jejunoileal bypass
  • Persons who weigh less than 90% of their ideal body weight
  • Cigarette smokers and persons who abuse drugs or alcohol
  • Populations defined locally as having an increased incidence of TB disease, possibly including medically underserved or low-income populations [5]

TB Control and Prevention

Individual Level

  • Keep your immune system strong by eating healthy and exercising
  • Avoid exposure to people known to who have active TB.
  • Surgical masks should be worn by patients with active TB to prevent infectious droplets from being expelled into the air.
  • Only consume pasteurized milk products.
  • Travellers at higher risk should have a pre-departure tuberculin skin test (TST) and be re-tested upon their return home.
  • Those at increased risk should also consult their healthcare provider to determine if the Bacillus Calmette-Guérin (BCG) vaccine is recommended [2].

Community Level

There are several critical factors that need to be taken into account to implement an effective tuberculosis control and prevention program to protect the community.

  1. Significant resources including public health infrastructure and personnel are required to enact and sustain tuberculosis control programs. Sustainability is critical because control of this disease requires a long-term effort. As such, a strong commitment by government agencies, which can mobilize the necessary resources and infrastructure, is essential for regional control of tuberculosis.
  • Rigorous case finding and treatment is obviously critical to save the affected individuals as well as stop transmission of infection to contacts. Case identification must combine microscopy and clinical symptoms, and treatment should consist of the short-course of directly observed therapy (DOTS) elaborated below.
  • Exhaustive contact tracing for contacts of each active tuberculosis case should be carried out in the field so that new infections can be identified and treated before becoming active cases.
  • A good surveillance system is fundamental to the control of any infectious disease. An administrative system for recording cases and monitoring outcomes is necessary to estimate the occurrence of disease and identify temporal trends and spatial clusters.
  • An adequate supply of tuberculosis medications must be available to populations with endemic tuberculosis. This may seem obvious, and it is, but unfortunately the lack of a consistent supply of medication has hampered many control programs particularly in poor areas of the developing world [3].

Technology

Germicidal ultraviolet lamps can be installed to kill airborne bacteria in buildings where people at high risk of tuberculosis live or congregate. A germicidal lamp is an electric light that produces ultraviolet C (UVC) light. UVC light kills tuberculosis bacteria, including drug-resistant strains, by damaging their DNA so they cannot infect people, grow or divide [6].

TB Treatment

Treating tuberculosis requires a long-term commitment. Specifically, at least 6 months of treatment are required because of the heterogeneous population of M. tuberculosis in an infected individual, which is composed of bacteria in active and dormant states. Medication that is effective against active mycobacteria may not work against latent mycobacteria and, thus, extended treatment ensures that the whole population of M. tuberculosis will eventually be exposed to the drug. Inactive tuberculosis may be treated with an antibiotic, isoniazid (INH), to prevent the TB infection from becoming active. Active tuberculosis is treated, usually successfully, with isoniazid in combination with one or more of several drugs, including rifampin, ethambutol, pyrazinamide, and streptomycin.

However, drug-resistant TB is a serious, as yet unsolved, public-health problem, among several regions including Africa. Undergoing treatment over a long time favors the emergence of drug-resistance gene mutations in the M. tuberculosis population.

Thus, at least two effective drugs must be administered: this reduces the probability of developing drug-resistant bacilli.

Poor patient compliance, lack of detection of resistant strains, and unavailable therapy are also key reasons for the development of drug-resistant TB. Non-adherence can lead to treatment failure in the individual as well as the development of antibiotic resistant forms of M. tuberculosis.

Therefore, adherence to treatment with the full regimen is essential for treatment success. To effect complete resolution of infection in the individual and mitigate the spread of antibiotic resistance in the population, WHO recommends the short-course strategy of directly observed therapy (DOTS) regimen, comprised of four drugs (typically isoniazid, rifampicin, pyrazinamide, and ethambutol) for two months, followed by two drugs (typically isoniazid and rifampicin) for four months.

DOTS regimen requires a healthcare worker to monitor each tuberculosis patient closely and observe the patient taking each dose of anti-tuberculosis medication to ensure proper compliance [3].

References

1 https://www.who.int/publications/m/item/united-republic-of-tanzania-tb-community-network-a-platform-for-a-stronger-community-response-to-tuberculosis

2 https://www.iamat.org/country/tanzania/risk/tuberculosis

3 http://www.infectionlandscapes.org/2013/04/tuberculosis.html

4 https://www.thetruthabouttb.org/latent-tb/what-is-latent-tb/

5 https://www.cdc.gov/tb/webcourses/tb101/page121.html

6 https://www.everydayhealth.com/tuberculosis/guide/risk-factors-causes-prevention/

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