Introduction
Mycobacterium tuberculosisis the known causative agent of tuberculosis. Tuberculosis is a common and deadly infectious disease that is caused by species of various strains of mycobacterium tuberculosis infective to man and animals. The tubercle bacilli of tuberculosis were demonstrated by Robert Kach in 1882. It show that the organism unique coat made it difficult to visualized earlier until a specific strain called the Ziehl Neelsen stain was discovered, since it took up the red acidic dye it is called acid fast bacilli (AFB)(Ochei and Kolhatkar, 2007).
It usually affects the lungs but can also affects other parts of the body where it causes tubercles characterized by the expectoration ofsputumin form ofmucus. Tuberculosis is contracted by people who have low immunity and those that have been compromised due to higher exposure to immunosuppressive drugs use or Acquired immune deficiency syndrome. Tuberculosis can be transmitted through inhalation or ingestion of bacteria. Most of the symptoms are weight loss, fever, night sweat, fatigue and chest pain.
Tuberculosis is often chronic (long-lasting) contagious disease. Tuberculosis often affects persons between 15 – 35 years of age and children especially those who have weak immunity, poorly nourished or those living with affected persons(David et al., 2007).
Tuberculosis can be inhaled when people sneeze, spit out cough. The inhaled bacterium passes directly to the lungs to produce a primary complex (tubercle focus) and extend to the lymph nodes within the chest (Konstntinos, 2010). This bacillus takes weeks or months to make an adult ill. The tubercle bacilli produce a chronic inflammation to the lungs, the pleural covering the lungs and body tissue and it also destroy the capillaries which leads to haemoptysis.
Conceptual framework
Tuberculosis is an infectious disease caused by a bacillus mycobacterium an Acid Fast Bacilli (AFB) it is a mammalian species in contract with human. Man is the only reservoir of the organism, it is an infection which is affecting more than 18.7 million cases and about 14,874 cases was reported in the United State of contracting tuberculosis mostly due to their immune system which are compromised by immunosuppressive drugs (Jasmer, Nahid and Hopewell, 2002), It is a disease that affects mostly the poor group in the society due to the overcrowded way of living and poor nutrition. Due to improved immunization programmed in children, the disease affect mostly adult and it takes a longer period to treat an infected person.
When this tubercle bacillus has been inhaled it passes directly to the lung to produce primary complex and it is extended to the lymph nodes within the chest. If the tubercle get to the alimentary canal through the mouth they infect the circulating mucosa of the lymph node of the neck which drains the throat but if the system body resistance is sufficient and high then the lung tissue will form tubercle which breakdown to form pus as part of sputum (Jasnieret al., 2002) .It can be recognized by direct staining of sputum or other specimen which is still the most important diagnosis method in developing countries and mycobacterium can withstand weak disinfectant and survive in a dry state for some weeks. In nature the bacterium can grow only within the cells of host organism but mycobacterium tuberculosis can also be cultured invitro (Parish and Stoker, 1999).
Mode of transmission of tuberculosis
Most infections in human result in a symptomatic, latent infection which will eventually progress to active disease which if left untreated kills more than half of its victims. The incubation period of the disease is 4-6 weeks through which there is manifestation of the signs and symptoms of tuberculosis (Akinsola et al., 2001).
Transmission is by inhalation of droplet particles when infected people cough, spit, sneeze, using same cup, towel, even living with an infected person and expel of infectious droplets. A single sneeze releases a lot of droplets of 0.5µm to 5µm in diameter transmit the disease since the infectious dose of tuberculosis is low and inhaling less than ten bacteria may cause an infection. When inhaled it passes directly to the lungs to produce primary complex and extend to the lymph nodes within the chest and if the bacilli get to the alimentary canal through the mouth they infect the mucosa of the lymph node of the neck which drains the throat.
The probability of transmission from one person to another depends upon the number of infectious droplet expelled by a carrier, the effectiveness of ventilation duration of exposure and virulence of the mycobacterium tuberculosis strain. The chain of transmission can be broken by isolating patient with active disease and starting effective anti-tuberculosis therapies. After two weeks of treatment people with non-resistant active tuberculosis generally cease to be contagious. It takes at least twenty one (21) days if someone that is newly infected can transmit the disease to others. Tuberculosis can also be transmitted by eating meat infected with tuberculosis.
Types of tuberculosis
Tuberculosis (TB) may be regarded in two categories active disease or latent infection. The most common form of active tuberculosis is lung disease, but it may invade other organs, so-called “extra pulmonary Tuberculosis”.
- Active tuberculosis disease
Active tuberculosis is an illness in which the tuberculosis bacteria are rapidly multiplying and invading different organs of the body. The typical symptoms of active tuberculosis variably include cough, phlegm, chest pain, weakness, weight loss, fever, chills and sweating at night. A person with active pulmonary tuberculosis disease may spread tuberculosis to others by airborne transmission of infectious particles coughed into the air.
- Latent tuberculosis infection
Many of those who are infected with tuberculosis do not develop to overt disease. They have no symptoms and their chest x-ray may be normal. The only manifestation of this encounter may be reaction to the tuberculin skin test (TST) or interferon –gamma release assay (IGRA). However, there is an ongoing risk that the latent infection may escalate to active disease. The risk is increased by other illnesses such as HIV or medications which compromise the immune system. To protect against this, the United States employs a strategy of preventive therapy or treatment of latent tuberculosis infection.
- Causes of tuberculosis
The primary cause of Tuberculosis is mycobacterium tuberculosis. Tubercle bacillus was discovered by (Robert et al., 1882). It is an aerobic bacterium that divides every 16-20 hours, an extremely slow route compassed with other bacteria which usually divide in less than an hour (Cox, 2004), Mycobacterium tuberculosis is a small red-like bacilli that can withstand weak disinfectants and survive in a dye sate for weeks. In nature, the bacterium can grow only within the cells of a host organism but mycobacterium tuberculosis (MTB) can be cultured invitro. It has a cell wall but lacks a phospholipids outer membrane; it is classified as a grain positive bacterium. However, if a grain stain is performed MTB either stains very weakly grain positive or does not retain dye due to the high lipid and mycolic acid content of its cell wall (Mardisen, 2001).
Pathogenesis of tuberculosis
Tuberculosis begins when the mycobacterium reach the pulmonary alveoli, where they invade and replicate within the embosoms of alveolar microphage. Tuberculosis affects any part of the body through blood stream to tissue and organs. The primary site of the infection is the lungs called the Ghonfocus and it is located either at the upper of the lower lobes or the lower part of the upper lobes of which bacteria are picked up by dendrite cells which do not allow replication, though cells can transport the bacilli to local part (Kumar et al., 2007).
When the bacteria gain entry into the blood stream, it damaged tissue. It spread through the body and set up many foci of infection all appearing as tiny white tubercle in nature. About 90% of the infected have a symptomatic, latent tuberculosis infection with only 10% lifetime chance will progress to tuberculosis diseases. People with this disseminated tuberculosis have a fatality rate of 100% if untreated (Nnoaham and Clark, 2008).
Epidemiology of tuberculosis
Tuberculosis is the world’s greatest infectious killer and the leading cause of death among people with HIV/AIDS. Tuberculosis has evolved with humans for many thousand years, the oldest known humans remains showing signs of tuberculosis infection are 9,000 years old (Hershkovite et al., 2008).
According to World Health Organization one third of the world’s population has been exposed to tuberculosis infection (W.H.O., 2009). In 2014, 9.6 million people around the world became sick with tuberculosis disease and there were 1.5 million related deaths worldwide. However, not all infections with mycobacterium tuberculosis cause tuberculosis disease and many infections are asymptomatic. In 2007 there were an estimated 13.7 million chronic active cases and in 2010 there were 8.8 million new cases and 1.45 million deaths, mostly in developing countries (W.H.O., 2009). The prevalence of tuberculosis per 100,000 people was highest in sub–Saharan Africa and was also relatively high in Asia accounting for 58% globally. The distribution of tuberculosis is not uniform across the globe; about 80% of the population in many Asian and African countries test positive in tuberculin test, which only 5-10% of the U.S population test positive(Mitchell, 2007).
In 2007, the country with the highest estimated incidence rate of tuberculosis was Swaziland with 1200 cases per 100,000 people. As of 2014, India has the largest total incidence with an estimated 2.2 million new cases. India has more than 0.3 million deaths every year.
In developed countries, tuberculosis is less common and is mainly an urban disease. In the United Kingdom, the national average was 15 per 100,000 in 2007 and the highest incidence rates in Western Europe were 30 per 100,000 in Portugal and Spain. These rates compared with 98 per 100,000 in china and 48 per 100,000 in Brazil while in the United States, the overall tuberculosis case rate was 4 per 100,000 persons in 2007. In Canada, tuberculosis is still endemic in some rural areas. (Al–Azen et al., 1998).
The incidence of tuberculosis varies with age. In Africa tuberculosis affects adolescents and young adults (W.H.O.). Tuberculosis is mainly a disease of older people or of the immune-compromised.
Nigeria has one of the highest tuberculosis burden in the world with estimated incidence of 133 per 100,000 (WHO, 2010). A study conducted in Umuahia by Nwachukwu et al., it was reported that the overall prevalence of Mycobacterium tuberculosis infection was 21.6%. Other states inNigeria, their prevalence are Kano 12.0%, Abeokuta 16.7%, Enugu 14.0%, Borno 27.0%, Plateau 30.0% and Benue 35.0% (Federal Ministry of Health, 2000). Higher infection rate for tuberculosis infection among male in Benin and Irua, Nigeria was reported (Nnorom et al., 1996).
Two hundred and five(205) patients suspected of having HIV and tuberculosis where prospectively studied in Kwale, Agbor and Eku in Delta State Nigeria from February 2006 to February 2008. It was determine using Zeihl Neelsen staining technique. A health point prevalence rate was obtained 49.3 percent and TB positive subject where statistically significant among the suspected subject (Jemikalajah and Saudi, 2009).
Signs and Symptoms of tuberculosis
The disease when active 75% of the cases are pulmonary tuberculosis (tuberculosis in the lungs).
Symptoms include:
- Chest pain
- Weight loss
- Prolong cough
- Night sweating
- Appetite loss
- Coughing up blood
- Presence of purulent
- Mucopurulent
Diagnosis of tuberculosis
The clinical presentation of tuberculosis is usually characterized by lungs collapse (making the physical appearance of the chest reveal abnormally). The diagnosis depends on identification of mycobacterium on a direct staining of sputum or secretion on culture of organism (Gordon et al., 2010).
Most of the patient develops symptoms every 16 to 20 hours in a day at the initial infection (Coker, 2000). The main problem of tuberculosis diagnosis is the difficulty in culturing this slow growing organism in the laboratory. A complete medical evaluation for tuberculosis must include a medical history, a physical examination, a chest x-ray, microbiological smears and cultures. It may also include a tuberculin skin test, a serological test. The interpretation of the tuberculin skin test depends upon the person’s risk factors for infection and progression to tuberculosis disease (Chome, 2000).
Prognosis of tuberculosis
Prognosis from tuberculosis infection to tuberculosis disease occurs when the TB bacilli overcome the immune system defenses and begin to multiply. In primary TB disease 1-5% of cases occur soon after infection (Kumar et al., 2007).
However, in the majority of cases, a latent infection occurs that has no obvious symptoms (Kumar et al., 2007). These dormant bacilli can produce tuberculosis in 2-23% of theses latent cases, often many years after infection (Parrish et al., 1998).
Vaccines for tuberculosis
Many countries use Bacilli Calmetle-Guerin (BCG) vaccine as part of their TB control programs, especially for infants. According to the W.H.O, this is the most often used vaccine worldwide with 85% of infants in 172 countries immunized in 1993 (W.H.O., 1995). This was the first vaccine for Tuberculosis developed at the Pasteur institute in France between 1905 and 1921 (Bonah, 2005).
BCG provides some protection against serve forms of pediatric tuberculosis, which account for most of the disease burden worldwide. There is an urgent need for a newer effective vaccine that would prevent all forms of tuberculosis including drug resistant strains in all age groups and among people with HIV (Sadoff and Jerry, 2006).
Generally, new vaccines to protect tuberculosis infection are been developed. The first recombinant tuberculosis vaccine rBGC 30, entered clinical trials in United States, it was sponsored by national institute of allergy and infectious disease (NIAID) in 2004.
Treatment of tuberculosis
Treatment for tuberculosis uses antibiotics to kill the bacteria. The two antibiotics commonly used are refampian and isomazid. However, instead of the short course of antibiotics typically used to cure other bacterial infection. Tuberculosis requires longer period of treatment (6-12months) to entirely eliminate mycobacterium from the body (Chome, 2000) Latent tuberculosis treatment usually uses a single antibiotic while active tuberculosis disease is best treated with combinations of several antibiotics to reduce the risk of the bacteria developing antibiotics resistance. People with latent infections are treated to prevent them from progressing to active tuberculosis disease later in life (Brien, 1994).
A patient with fully susceptible tuberculosis develops secondary resistance during tuberculosis therapy because of inadequate treatment, not taking the prescribed regimen appropriately or using low quality medication (Enayat, 2004).
Prevention and control of tuberculosis
Prevention and control of tuberculosis comes in two ways. Firstly, people with tuberculosis and their contacts are indentified and then treated; secondly, children are vaccinated to protect them from tuberculosis.
The World Health Organization (W.H.O.) declared tuberculosis a global emergency in 1993 and the stop tuberculosis partnership developed a global plan to stop tuberculosis that aims to save 14 million lives between 2006 and 2015 (WHO, 2006). Since humans are the only host of mycobacterium tuberculosis, eradication would be possible, a goal that would help greatly by and effective vaccine (Maryin, 2006).
References
Ajoke, C. N., Nwachukwu, N. Idenyi, J. N. Ugwuja, E. I. and Nwachi, E. U. (2010). Epidemiology of pulmonary tuberculosis in some parts of Abia State, Nigeria. Asian Journal of Epidemiology 2:13-19.
Akinsola, M. (2001). “The major Infectious Diseases in the World to treat or not to treatN. Engl. J. Med, 845 (3): 208-10.
Al-Azem, A., Kaushal,S.M., Turenne, C., Hoban, D.,Hershfiled,E. Macmorran, J. and Kabani, A. (1998). Rural outbreaks of Mycobacterium tuberculosis in a Canadian province
Brien, R. (1994).Drug-Resistance: Tuberculosis Etiology, Management and Prevention”. Semin Respiration Infection 9 (2): 104 – 12.
Cox, R. (2004).Quantitative relationship for specific growth rates and macromolecular compositions of mycobacterium tuberculosis, Microbiology 150 (5): 1413 – 26.
Chome, G. (2004). Centers for Disease Control and Prevention (CDC).Division of Tuberculosis Elimination. Care corrigendum on Tuberculosis: What the Clinical should known, 4th Edition pp205-210.
Coker, M. (2000).Detection and the control of Tuberculosis.New York: St. Martins Press.
David, W., Carol, T., Jane, M. and Andrew.P. (2000).Mycobacterium Tuberculosis (11th ed.) where there is no Doctor, 10:189-192.
Douglas, A., Strachn, D. and Maxwell, J. D (1996).Seasonality of tuberculosis; the reverse of other respiratory diseases in the UK.
Enayat, F. (2004) Emergence of Mycobacterium Tuberculosis with Extensive Resistance to second – time Drugs – World widepp52 – 60.
Nnorum, J. A., Esu, W. E. and Tilley-Gyado, A. (1996). HIV, tuberculosis and syphilis in Nigeria: A descriptive study international conference on AIDS. Int. Conf AIDS July 7-2, 11, 138.
Ochei, J. and Kolhatkar, A. (2007).Medical Laboratory Science Theory and Practice.Tata McGraw Hill publishing Company Limited
Jasnier, R. M. Nahid, P. and Itope, P.C. (2002).Clinical Practice. Latent Tuberculosis Infection N, Eng. J. Med, 347 (23): 1860-6.
Kostantious, A. (2010). Testing for Tuberculosis” Australian prescribes 33:12-18.
Kumar, V., Abbas, A. K. Fausto, N. and Mitchell, R. N. (2007).Robbins Basic Pathology (8th Ed.) Sanders Elsevier pp516-522.
Martieneau,A.R., Nhamoyebonde, S., Oni, T.,Rangaka, M.X., Marais, S.(2011). Reciprocal Seasonal Variation in Vitamin D Static and Tuberculosis notification in cape Town, South Africa.Medical Research Council, Origin of the MRC. 2006
Parish, T. and Tocker, N. (1999). Mycobacteria Bugs and Bugbears (Two Stops Forward and One Step Back)MolBiotechnol 13(3): 191-200.
Parrinello,C.M., Crossa, A. and Harris,T.G. (2012) Seasonality of Tuberculosis in New York City
Sadaff, M and Jerry, H. (2006): Advance in Tuberculosis Vaccines Strategies Nature. Review Microbiology 8: 150 – 156.
World Health Organization (2015) “The Step Tuberculosis Strategies, Case reports, treatment outcomes and estimates of Tuberculosis Burden. Global tuberculosis control, epidemiology strategy, financing Pp 167 – 300.
