Tuberculosis

Introduction

General Information

Tuberculosis (TB) is a contagious disease caused by the bacteria Micobacterium tuberculosis. It is a disease that primarily affects the pulmonary system (lungs) but can also affect the kidneys, spine and brain. It can manifest itself in one of two stages - latent (dormant) and active (acute). Those in the latent stage can progress to the active stage when their immune system is compromised by other factors such as HIV/AIDS, diabetes, substance abuse or severe kidney disease to name just a few. The World Health Organization (WHO) states that 5-10% of infected patients will enter the acute stage at some point in their lives. TB is treatable disease.^[1] The regions of greatest risk are Southeast Asia, Sub-Saharan Africa and the Western Pacific. Due to the increasing HIV/AIDS epidemic, TB has also become more prevalent.

TB is most commonly spread through airborne transmission similar to that of the common cold (sneezing or coughing). Only persons in the active (acute) stage of the disease can infect others. If left untreated, TB can be fatal. Transmission usually takes a prolonged exposure to an infected person. Though not normally contracted through food, it should be noted that cattle can also be affected by the disease. The consumption of unpasteurized milk from an infected animal can be a source for transmission to humans.^[2][3]

MDR-TB and XDR-TB Information

Multi-Drug-Resistant TB (MDR-TB) and Extensively-Drug-Resistant (XDR-TB) have become more prevalent in recent years. MDR-TB develops in patients who's first-line treatments were mismanaged or misused. This means the wrong combination of medications were administered and/or the treatment was not completed by the patient because they felt better. When this occurs, the patient can possibly spread the resistant bacteria to others. The first-line drugs are Isoniazid and Rifampicin. Currently, XDR-TB is still quite rare and develops when both first-line and second-line treatments have been mismanaged/misused. Again, a patient with active XDR-TB can spread the resistant bacteria. The XDR-TB will be resistant to Isoniazid, Rifampicin, any Fluoroquinolone and one of the following: Capreomycin, Kanamycin or Amikacin. XDR-TB is most prevalent in patients with HIV/AIDS (with or without HIV/AIDS treatment) who have been infected with TB. Approximately 15% of MDR-TB patients will develop XDR-TB, with the highest concentration of infected people currently reported in Europe. There are no reported differences in the speed in which one contracts any of the forms of Tuberculosis.^[4]

Prevention

At the present time, the Bacille Calmette-Guerin (BCG) vaccine is used mainly for infants and children in countries where TB infection rates are high. It is not recommended for general use in adults because it does not demonstrate consistent immunity against pulmonary TB and it can potentially interfere with the tuberculin skin test reactions. Use in health care workers is considered on a case to case basis.^[2][5]

Symptoms and Treatment

Symptoms

Latent Tuberculosis
Persons with latent TP will demonstrate no symptoms of the disease. They will, in most cases, react with a positive result to the tuberculin skin test and/or the QuantiFERON-TB® Gold test. Chest x-rays and sputum tests will usually be normal. These patients can not transmit TB to others. A latent TP patient can develop active TB if not treated during the dormant period.^[3]

Active Tuberculosis
Persons with active TP will display symptoms which include a severe cough lasting 3 weeks or longer, chest pain, presence of blood and/or sputum during coughing, fatigue, weight loss, fever, chills and night sweats. They will, in most cases, react with a positive result to the tuberculin skin test and/or the QuantiFERON-TB® Gold test. Chest x-rays and sputum tests will usually be abnormal. These patients can transmit TB to others.^[3]

Treatment

Latent Tuberculosis
The recommended treatment for latent TB is the administration of Isoniazid daily over a six month period. The patient will be monitored monthly while under treatment. Side effects include skin rash, nausea and possible liver disease. Completing the treatment regimen is crucial as incomplete treatment can lead to the development of MDR-TB.^[2][6][7]

Active Tuberculosis
The recommended treatment for active TB is the administration of Isoniazid, Rifampin, Ethambutol and Pyrazinamide daily for up to 9 months. The treatment regimen will depend on the severity of the infection. Patients will be monitored regularly during the treatment and follow-up periods. Incomplete treatment regimens can lead to the development of MDR-TB. Sputum tests will be conducted regularly to monitor progress and for the presence of the bacteria.^[2][6][7]