Tuberculosis

Tuberculosis (TB) is a treatable and curable disease, but it is easily transmissible. It has become a global disease problem and collaborated mitigation efforts are in place. In the previous decades, TB was feared because it was belied that it has not cured. However, there have been several successful discoveries that have aided in comprehending the disease, improving diagnoses procedures and in its management. Close to 9.6 million people acquired TB in 2014, and out of these, 1.4 million died despite the current efforts to control its transmission. Even though the incidence of TB seems to have reduced, it is an aggressive disease that requires prompt treatment under strict supervision. However, it does not mean that every exposure to TB bacteria causes TB like in the case of latent TB, but the situation is different for people with a weak immune system and the elderly. This paper discusses the origin of tubercle bacilli (causative agent for TB), its method of spread, disease burden globally, control and treatment of the disease, and training efforts put in place to control spread.
Keywords: Tuberculosis (TB), WHO (world health organization), Tubercle bacilli
Introduction
Tuberculosis (TB), caused by Mycobacterium tuberculosis, is associated with the respiratory system because it attacks the lungs. However, according to Schuenemann et al. (2013), it can also affect other parts of the body including, the spine, brain, and kidneys. Having the bacteria in the body doesn’t necessarily present the disease (latent TB infection).

According to Daniel (2011), various studies have been conducted to indicate the origin and investigate the first cases of tuberculosis. Evidence of what is regarded as the earliest discovery of TB has been presented by genotype isolation in human and animal remains (Schuenemann et al., 2013). In this, skeletal specimens from fossils are studied using the molecular DNA testing techniques in case there is a lesion that is highly suggestive of the TB disease. According to researchers, evidence suggests that man first acquired TB in Africa about five centuries ago. The disease was then spread to the rest of the world along trade routes. Hunters are believed to be the first people to contract the disease.
Evidence of early understanding and treatment of TB between 17 -19th centuries is available (Natarajan et al., 2011). During these times, different people used specific names for the disease. For instance, Hippocrates termed the disease as phthisis, which according to him, it was characterized by exhaustion, excess phlegm, cough, wasting, and fever. Other terms used to describe TB in ancient times include Scrofula, white plague, consumption and Pott’s disease (Natarajan et al., 2011). Treatment methods employed at this age involved the use of plant products such as myrrh, black pepper, frankincense, hyssop, and acacia among others. Galen used bloodletting to try and cure the disease. He was the first to see the tubercles between 129-210 BCE.
Currently, there is advanced understanding of the disease, its cause, and management. This insight resulted from breakthroughs that gave hope to finding a cure after several trials done across the centuries (Schuenemann et al., 2013). Several scientists have contributed to this success in various ways, for example, in the invention of testing techniques like auscultation, use of X-rays and discovery of medication that are effective on Mycobacterium tuberculosis. Notably, these scientists included Rene Laennec (stethoscope), Jean Antoine Vilemin (described contagious nature of the disease), Robert Koch (postulates of causative agents-bacteria) and Wilhel Roentgen (X-ray).
Symptoms
TB primarily affects the lungs and therefore most of the symptoms relate to this area. However, as mentioned earlier on, the disease can affect other parts of the body, and under such circumstances, the symptoms are varied. The most salient symptom of Pulmonary TB is a persistent cough (Centers for Disease Control and Prevention (CDC), 2013). A cough can produce sputum and sometimes blood when it has affected deep into the lungs. There might be a pain in the chest, which worsens when one coughs. Other symptoms might not be directly related to TB; hence, it is paramount to perform further to ascertain the presence of the TB-causing bacteria. Such investigations are especially required whens other parts of the body (not the lungs) are thought to be infected. These symptoms include (CDC, 2013, 6):
Excessive Sweating at night
Unintentional weight loss
Decreased appetite
Chills
Fever
General body malaise or fatigue
Individuals with latent TB are asymptomatic and cannot pass on the infection to other people (CDC, 2013). Likewise, they do not feel unwell, and at most times, the infection never progresses to the actual disease. Unfortunately, some groups of people with latent TB can develop the disease, and these categories include:
The elderly.
Very young children/babies.
People with HIV/AIDs.
People with weakened immune system.
People who have recovered from TB but was not correctly treated in the past.
Causes of TB
Robert Koch is the scientist behind the isolation of Mycobacterium tuberculosis, which is the causative agent of TB (Schuenemann et al., 2013). He used solid culture media to isolate the bacteria after culture broths proved not effective and time-consuming in demonstrating the presence of the organism. While using this testing method, Robert Koch discovered that the bacterium was rod-shaped and resembled the leprosy bacilli. According to Natarajan, Kundu, Sharma, and Basu (2011), Robert Koch was also able to demonstrate that the bacteria could survive intra-cellularly or extra-cellularly. This knowledge enabled him to inoculate rats and test animals with sputum and pus from infected people during his studies. Earlier on, there had been some progress from the work of other scientists trying to figure out the causes of the disease and associated treatment. A French doctor named Jean-Antoine Villemin demonstrated that TB was transmissible by inoculating tuberculous matter form cadavers into laboratory rats who later acquired the infection.
Currently, diagnosis of the disease has been made easier with advancement of knowledge of the disease, and technology (Natarajan et al., 2011). The World Health Organization has laid guidelines on how to detect TB, and the necessary tests are done to confirm the presence of the disease. A person with a prolonged cough lasting more than three weeks should be done a chest radiographic examination for evaluation of abnormalities suggestive of TB. Sputum should be collected for Acid-fast bacilli (AFB) smears and culture. Mantoux test, a skin test, has now been adopted as a core test for determining if an individual is infected with TB. In this case, TB antigens are injected into the skin and a reaction of the skin occurring within 24 hours is confirmatory of the infection.
Method of Transmission and Pathogenesis
The majority of TB transmissions occur through airborne droplet inhalation of content containing the Mycobacterium tuberculosis complex (Zumla, Raviglione, Hafner, & von Reyn, 2013). This kind of transmission occurs when TB-infected individual sneezes, speaks, sings, or coughs and by so doing, disperses the infected droplets into the air. Persons breathing the same air, nearby, inhale the droplets containing the bacteria and sometimes become infected. TB can also be spread through other means, but these are rare. For instance, it can be spread through direct inoculation or oral ingestion. Oral transmission can occur when a person consumes raw milk that contains Mycobacterium bovi (the strain that is found in animals, such as cows and goats). This method of transmission has been solved by pasteurization of milk or boiling it before consumption (Daniel, 2011).
Despite the fact that transmission of the bacteria to another person may occur, development into active disease does not always occur. However, it can become latent, or with a strong immune system, the body can get rid of the causative agent from the system. Whether exposure to the TB bacterium will cause infection or not is determined by several individual characteristics, some of which are indicated below:
The patient is the source if he or she has positively tested sputum and increased the frequency of coughing.
Exposed person- BCG vaccination, their innate immunity that is the primary body protection mechanism, and genetic susceptibility are influential.
Exposure- this depends on ventilation, frequency of exposure and duration.
Virulence of the strain of TB- Beijing type is highly infectious.
People in close contact with the infected person are exposed to a higher risk of acquiring the infection (Daniel, 2011). This case is especially true for family members, co-workers, friends and roommates due to prolonged duration of exposure. The elderly, very young children and babies, people living with HIV/AIDs, and people with a weak immune system due to diseases such as diabetes or leukemia should be protected from exposure because they can easily contract the disease. This category also includes people who have recovered from TB that was not correctly treated in the past.
Pathogenesis
Natarajan et al. (2011) state that when an individual inhales the droplets infected with tubercle bacilli, they enter the lungs and travel further down to the alveoli. The environment in the alveoli allows the bacteria to multiply. From here, some tubercle bacilli can enter the bloodstream from where they are transported to the other parts of the body. If the bacteria reach susceptible parts, for example, the brain, lungs, bone or the kidneys, they are likely to cause infection here. In a period of two to eight weeks, the body’s immune system generates protective immune cells (macrophages) that fight the bacteria by creating a barrier shell around the tubercle bacilli to keep it contained (latent TB). A weak immune system increases the body’s vulnerability and fosters active infection and rapid multiplication of the bacteria to the extent that it infects other organs. Subsequently, symptoms such as a cough appear.
How to contain TB
Prevention of TB infection is the best way to curb the menace caused by disease burden due to TB infection and treatment. Hence, various approaches have been devised as discussed below.
Environmental controls
‘Environmental controls’ is a term used purposefully to refer to engineering technologies aimed at bringing down the risk of spread of TB and limit the introduction and concentration of TB infectious droplets in the air. One of the ways to do this is by promoting good ventilation in building constructions especially in public health clinics, homeless shelters, and overcrowded areas. Ventilation is a credible mitigation measure that helps to dilute contaminated air. Halls and buildings should allow consistent air entry and subsequent dilution of any air pollutants through natural ventilation or fans.
Administrative controls
These refer to administration efforts and policies enacted to control the spread of TB. They include:
Training and counseling staff on TB.
Routine screening in case of risk of exposure.
Assessing TB risk in the building set ups.
Formulation and commitment to implementation of TB control policies that include aim to prevent, cure, and protect uninfected individuals
Work practice control.
It also may include patient respiratory protection whereby identified or highly suspicious cases wear protective masks to block aerosols when talking, coughing and breathing. The next step is to isolate persons with suspected infectious active disease till proper treatment is commenced. Fast tracking to treat newly infected individuals can be adopted as well. People attending to or close to suspected infectious cases should wear protective gear that includes masks and gloves when interacting with the patient or getting into contact with contaminated surfaces.
Vaccination with Bacilli Calmette-Guerin (BCG) vaccine.
In most countries with high incidences of TB infection, BCG vaccine is given routinely to prevent tuberculous miliary disease and meningitis since childhood. However, this is not the case in the United States due to the low prevalence of the disease (CDC, 2013). The vaccine is recommended for children at a risk of exposure from sick adults or who have not sought treatment or are ineffectively treated. Another category of people who require the vaccine are the health care workers who work with TB patients or where infection-control precautions for TB have not been successfully implemented.
The successful implementation of the above methods can help to control the spread of TB, immensely. Thereby, resulting in the reduction of mortality and morbidity rates attributed to the disease. The cost of managing TB would also be reduced.
Incidence
Tuberculosis affects people in all parts of the world, but its incidence is high in low income and middle-income populations. According to WHO (2011), Tuberculosis lies among the top ten diseases that kill people worldwide. The statistics show that 10.4 million people contracted TB in 2015 and of these, 1.8 million succumbed to the disease. HIV-infected people have a higher risk of dying from TB. The World Health Organization estimates that 35% of deaths caused by HIV result from TB disease.
Some countries have a high prevalence of TB and TB-related deaths. Last year, India was first in ranking while Indonesia, Nigeria, China, and South Africa followed. Together, these countries accounted for 60% of the global TB disease burden. Therefore, TB control will highly depend on the success of its prevention and management in these countries. The World Health Organization estimates that eradication of TB epidemic can be achieved by the year 2030 under sustainable development plan goals.
In the United States, the prevalence of TB has declined gradually (CDC, 2013). For instance, in 2014, TB cases reduced by 1.5%. The number of cases is influenced by such factors such as race, country of origin and age. An analysis of 2014 TB cases showed that persons of Asian origin were more than other groups of people, and they were followed by Native Hawaiians and Pacific Islanders. Foreign-born persons, especially those born in Mexico, India, China and Vietnam, also had a higher incidence of cases compared to Native Americans. Disease burden from TB has gradually reduced since 1993 to present. The greatest reduction is observed from the year 2000- 2015.
TB diagnosis, treatment, education, and prevention have a direct implication on cost, not only to individuals and countries but the entire world at large. Globally, most countries and especially those from the developing world rely heavily on external donor funding and support through the World Health Organization for implementation of TB control programs and purchase of supplies, including TB drugs. This funding is about 75% in countries with high TB burden and comes mainly from Global Fund, which helps in curbing AIDS, Tuberculosis, and Malaria. CDC (2013) estimates the treatment per patient for the drug-susceptible TB to be around US$ 100-1000 and US$ 2000-20000 for Multiple Drug-resistant TB.
Additional funding is channeled to TB research and development. Between the years 2005-2014, funding in this area was estimated to be around $ 0.7 billion per annum. WHO (2011) recommends the introduction of 4 new diagnostic tests after reviewing them this year. These include the two line probe assays (LPAs) for the detection of resistance to both first-line and second-line anti-TB drugs through the loop-mediated isothermal amplification test for TB (TB-LAMP). New developments: Xpert Ultra and GeneXpert Omni, are to be released in 2017. Several drugs and TB vaccines are in the process of trial, and these have cost implication on the budget for TB prevention and management programs. Other costs are incurred by the local and federal governments, as well as hospitals that care for TB patients. They include fees for hospitalization, investigations, treatment and follow-up. Establishment of infection control measures also raises the budget for TB care globally.
Treatment
Since TB is highly infectious in the first 2 weeks of infection, it is important to isolate patients in a negative pressure room during treatment. The medical staff attending to the patient is obliged to wear high-efficiency masks to filter out the tubercle bacillus. Sometimes, this is not practical in some countries; thus, TB continues to be an issue of public health concern. Tubercle Bacillus responds to specific antibiotic therapy. The WHO (2011) recommends the DOT (Directly Observed Therapy) for all patients taking TB drugs to promote adherence and prevent the rise of Multi-drug resistant TB. For initial TB treatment, a four Drug-regimen consisting of Rifampicin, Pyrazinamide, Isoniazid, and Ethambutol/Streptomycin is recommended. This regimen is given for 2 months after which Pyrazinamide and Ethambutol are withdrawn (if the isolate is fully susceptible). Isoniazid and Rifampicin are given for 4 more months.
For multi-resistant TB (MDR-TB), drug therapy should be commenced early, even before culture results are availed. The following drugs are prescribed according to strain susceptibility:
Pyrazinamide
Ethambutol
Cycloserine
Terizidone
Para-aminosalicylic acid
Rifabutin (substitute for rifampin)
A thioamide: Ethionamide, prothionamide
A fluoroquinolone: Ciprofloxacin, Levofloxacin, Ofloxacin
An aminoglycoside: Streptomycin, Capreomycin, Amikacin, kanamycin
A combination of 3-5 drugs is recommended. The treatment is continued for 18-24 months and patient should always be on DOT (CDC, 2013).
Treatment is way more costly than control especially for chronic diseases like TB. Therefore, educational efforts should be implemented for the general public, patients, and health care workers on how to prevent and contain the spread of TB. Of importance is to define what TB is and how the disease is spread to the general population. Most governments and the health organizations in the world has put in place educational materials that can be accessed by almost everyone and collaborations to fund and avail necessary support to ensure that educational needs of the people are satisfactorily met. According to WHO (2011), active TB patients should be taught on the need to adhere to the treatment regimen to prevent recurrence and spread to other people. Infection control measures are properly published to ensure that everyone is aware of their responsibility in preventing the spread of TB and increase of MDR-TB.
In conclusion, TB is a global menace which can be contained through personal responsibility in preventing new TB infections, worldwide collaboration in terms of control, financing and support. Prevention is the best strategy for containing TB burden though new technologies for diagnosis and treatment are discovered with intensified research.
References
Centers for Disease Control and Prevention (CDC). (2013). Guidelines for environmental infection control in health-care facilities: Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC). Atlanta, GA: Author.
Daniel, T.M. (2011). Hermann Brehmer and the origins of the tuberculosis sanatoria.
International Journal on TB & Lung Diseases. 15(2), 161-2.
Natarajan, K., Kundu, M., Sharma, P., & Basu, J. (2011). Innate immune responses to M.
Tuberculosis infection. Tuberculosis, 91(5), 427-31.
Schuenemann, V. J., Singh, P., Mendum, T. A., Krause-Kyora, B., Jäger, G., Bos, K. I., … & Krause, J. (2013). Genome-wide comparison of medieval and modern Mycobacterium leprae. Science, 341(6142), 179-83. doi: 10.1126/science.1238286.
World Health Organization (WHO). (2011). Guidelines for the programmatic management of drug Resistant tuberculosis: European Respiratory Journal, 38(3): 516-528.
Zumla, A., Raviglione, M., Hafner, R., & von Reyn, C. F. (2013). Tuberculosis. The New England Journal of Medicine, 368(8), 745-755.