Tuberculosis: Types, Symptoms, Treatment
Significance of the disease
Tuberculosis (TB) is one of the leading causes of death worldwide, which affects more than 10 million human lives every year [1].
1.3 million people are projected to die from tuberculosis each year [1].
The incidence of the disease is up to 400 per 100 000 people in certain countries [2].
Given the figures, it is essential to contain the spread of TB.
Global incidence of tuberculosis is decreasing slowly by 1.6% per year instead of the required 5% to meet WHO’s targets to end the disease [3].
Half a million people get infected with drug-resistant tuberculosis [2].
Given the lack of fast diagnosis and targeted therapies, the incidence of the disease is predicted to increase, especially in South Africa, China, and Russia [4].
Types of Tuberculosis
TB can be classified in three types: active, miliary, and latent form. It mostly affects the lungs, but can also develop in other organs such as bones, skin, kidneys, and liver [1].
The person with active TB can easily spread the disease to other people through droplets coughed into the air [1].
Miliary TB is a disease when bacteria get into the bloodstream and affect multiple organs simultaneously.
Latent TB is found in people who are infected with TB but do not show symptoms of it, and their chest X-ray may be normal. The only sign of this form is positive tuberculin test. Latent TB can turn into active form; preventive therapy is recommended [1].
Symptoms
Symptoms of lung TB include cough, chest pain, high body temperature, night sweating, fatigue [4]. A cough that lasts more than three weeks, loss of appetite, and weight loss are the most common symptoms.
Bone TB is characterized by pain at joints, back pain, carpal tunnel syndrome, neurological disorders, uneasiness in the thoracic region, and soft tissue swelling [7].
Transmission of TB
M. tuberculosis is carried in airborne particles, called droplet nuclei, which are 1– 5 microns in size [7]. Infectious droplet nuclei are produced when a person with pulmonary TB coughs or sneezes. These small particles can remain in the air for many hours.
Risk Factors
Risk factors that determine the probability of transmission of the disease include environmental and patient ones. Long exposure to bacteria in closed non-ventilated spaces increases the risk of infection. Improper specimen handling procedures place medical personnel at risk of acquiring infection. Positive air pressure in patient’s room may force infectious particles to spread elsewhere [6].
Patient factors include comorbidities, such as HIV infection, which is the greatest risk factor for the onset of TB in people with latent form because of suppressed immune system. Children under the age of 5 are also at risk. Also, immunosuppressive therapy such as tumor necrosis factor-alpha (TNF) antagonists or systemic corticosteroids, silicosis, diabetes mellitus, chronic renal failure, leukemia, or cancer are significant risk factors [6]. Patients after a gastrectomy or had a jejunoileal bypass, with insufficient bodyweight, smokers and substance abusers have increased chances of developing TB.
Complications
Tubercle bacilli are likely to join with blood and reach various body parts and systems, leading to the emergence of tuberculosis in organs such as “the brain, larynx, lymph node, lung, spine, bone, or kidney” [7].
Moreover, Mycobacteria may develop drug-resistance due to insufficient treatment and become very hard to eradicate. As a result, TB may cause pain in various parts of the body and organ failure (See Figure 2).
Pulmonary complications of TB can include “hemoptysis, pneumothorax, bronchiectasis, extensive pulmonary destruction, malignancy, and chronic pulmonary aspergillosis” [6]. TB meningitis may inflict headache and confusion, while TB of the spine may cause back pain. Kidney TB may result in necrosis of parenchyma and renal failure [6]. Overall, tuberculosis is a serious condition that may lead to deadly outcomes.
Diagnosis
TB blood tests (interferon-gamma release assays [IGRAs]) and Mantoux tuberculin skin test (TST) help to differentiate between TB-infected and healthy individuals. Since they do not differentiate between active and latent TB forms, additional examinations, such as X-ray and physical exam should be performed. Sputum should be collected for cell culturing to check for Mycobacteria. Additionally, whole-genome sequencing of sputum samples can be performed [6].
To complete medical examination, medical history, contacts with infected individuals, and symptoms of a patient should be collected. Physical examination, chest radiography, and a CT scan should be initiated. Patients with fibrotic lesions on a radiogram should take a blood test for TB. Three smears for acid-fast bacilli (AFB) should be taken to differentiate between latent TB and active one.
Protection
CDC recommended measures are aimed at protecting public health from TB [6].
Healthcare administrators should create control plan conduct employee training; ensure adequate supply of TB medication; ensure proper cleaning of medical equipment; apply proper environmental controls and filtration technologies.
Healthcare workers should wear the recommended protective equipment; coach and supervise patients during sputum collection and drug in-take; provide expert medical consultation to patients;
Law enforcement authorities should involuntarily isolate patients who are unwilling to complete treatment and educate population on respiratory hygiene.
Treatment
Isoniazid, rifampin, pyrazinamide, and ethambutol.
Intensive treatment for 2 months and 4-7 months of medication intake.
First phase: killing active bacilli to prevent bacterial resistance.
Second phase: eliminating surviving bacilli and preventing failure and relapse [6].
If patients are not treated long enough, the surviving bacilli can cause TB disease in the patients at a later time. Four months are the accepted duration for the second phase; however, seven months of treatment are recommended for patients with cavitary pulmonary TB and HIV patients who did not receive ART [6].
Vaccination
The bacilli Calmette-Guerin (BCG) vaccine from Mycobacterium bovis was introduced in 1921. The vaccine has no effect on IGRA. It is recommended for prevention of disseminated TB and TB meningitis in children [6].
References
Furin J, Cox H, Pai M. Tuberculosis. The Lancet, 2019;393(10181): 1642-1656.
WHO. Global tuberculosis report 2018. [Internet]. Geneva: The World Health Organization; 2018. Web.
GBD tuberculosis collaborators. The global burden of tuberculosis: results from the Global Burden of Disease study. Lancet Infect Dis, 2018 Mar;18(3): 261–84.
Hossain MS, Ahmed F, Andersson K. A belief rule based expert system to assess tuberculosis under uncertainty. Journal of medical systems. 2017 Mar 1;41(3): 43.
Ismail NA, Mvusi L, Nanoo A, et al. Prevalence of drug-resistant tuberculosis and imputed burden in South Africa: a national and sub-national cross-sectional survey. Lancet Infect Dis, 2018 Jul;18(7): 779–87.
Core curriculum on tuberculosis: what the clinician should know [e-book]. 7th ed. Atlanta: CDC; 2021. Web.
Narayana Health. Bone tuberculosis. [Internet]. Bengaluru: Narayana Health; 2020. Web.