Tuberculosis Article Index for
Tuberculosis
Articles about
Tuberculosis
Website Links For
Tuberculosis
 

Information About

Tuberculosis




  ICD10 A15-A19
  ICD9 -



Tuberculosis (commonly shortened to '''TB''') is an Infection caused by the Bacterium '' Mycobacterium Tuberculosis '', which most commonly affects the Lung s ( Pulmonary TB) but can also affect the Central Nervous System ( Meningitis ), Lymphatic System , Circulatory System ( Miliary Tuberculosis ), Genitourinary System , Bone s and Joint s.

Tuberculosis is one of the most deadly and common major Infectious Disease s today, infecting two billion people, or approximately one-third (1) of the world's population. Nine million new cases of the disease, resulting in two million deaths, occur annually, mostly in Developing Countries . However, Developed Countries are not spared the burden of tuberculosis. There is a rising number of people in the developed world who contract tuberculosis because they have Compromised Immune Systems , typically as a result of Immunosupressive Drugs or HIV/AIDS . These people are at particular risk of tuberculosis infection and active tuberculosis disease.

Most of those infected (90%) have kills 2-3 million.

The neglect of TB control programs, HIV/AIDS, and immigration has caused a resurgence of tuberculosis. Multiple drug resistant strains of TB (MDR-TB) and Extreme Drug-Resistance in Tuberculosis (XDR-TB) are emerging. The which aims to save an additional 14 million lives between 2006 and 2015.


OTHER NAMES FOR THE DISEASE



THE BACTERIUM

'' Mycobacterium Tuberculosis ''.]]
The cause of tuberculosis, '' Mycobacterium Tuberculosis '' (MTB), is a slow-growing Aerobic Bacterium that divides every 16 to 20 hours. This is extremely slow compared to other bacteria (although not the slowest), which tend to have division times measured in minutes (among the fastest growing bacteria is a strain of '' E. Coli '' that can divide roughly every 20 minutes; by contrast, Mycobacterium Leprae divides every 20 days). MTB is not classified as either Gram-positive or Gram-negative because it does not have the chemical characteristics of either. If a Gram stain is performed, it stains very weakly Gram-positive or not at all (ghost cells). It is a small rod-like Bacillus which can withstand weak Disinfectant s and can survive in a Dry State for weeks but, spontaneously, can only grow within a host organism (in vitro culture of M. tuberculosis took a long time to be achieved, but is nowadays a routine laboratory procedure).

MTB is identified microscopically by its staining characteristics: it retains certain stains after being treated with acidic solution, and is thus classified as an " Acid-fast Bacillus " or "AFB". In the most common staining technique, the Ziehl-Neelsen Stain , AFB are stained a bright red which stands out clearly against a blue background. Acid-fast bacilli can also be visualized by fluorescent microscopy, and by an Auramine-rhodamine Stain .

The ''M. tuberculosis'' complex includes 3 other , M. africanum, and ''M. microti''. The first two are very rare causes of disease and the last one does not cause human disease.

: Nontuberculous Mycobacteria (NTM) are other mycobacteria (besides M. Leprae which causes Leprosy ) which may cause pulmonary disease resembling TB, lymphadenitis, skin disease, or disseminated disease. These include ''Mycobacterium avium, M. kansasii'', and others.


THE DISEASE


Epidemiology

TB infects around 2 billion people in the world. The prevalence varies enormously throughout the world, from 356 per 100,000 in Africa to 41 per 100,000 in the Americas . In the UK, incidence is 90 per 100,000 in areas like the centre of Birmingham to less than 5 per 100,000 in rural Hertfordshire .


Transmission

TB is spread by aerosol droplets expelled by people with active TB disease of the lungs when they cough, sneeze, speak, or spit. Each droplet is 5 Micrometre in diameter and contains 1 to 3 Bacilli . Close contacts (people with prolonged, frequent, or intense contact) are at highest risk of becoming infected (typically a 22% infection rate). A person with untreated, active tuberculosis can infect an estimated 20 other people per year. Others at risk include foreign-born from areas where TB is common, Immunocompromised patients (eg. HIV / AIDS ), residents and employees of high-risk congregate settings, health care workers who serve high-risk clients, medically underserved, low-income populations, high-risk racial or ethnic minority populations, children exposed to adults in high-risk categories, and people who inject illicit drugs.

Transmission can only occur from people with active TB disease (not latent TB infection).

The probability of transmission depends upon Infectious ness of the person with TB (quantity expelled), environment of exposure, duration of exposure, and Virulence of the organism.

The chain of transmission can be stopped by isolating patients with active disease and starting effective anti-tuberculous therapy.


Pathogenesis

While only 10% of TB infection progresses to TB disease, if untreated the death rate is 51%.

TB infection begins when MTB bacilli reach the Pulmonary Alveoli , infecting alveolar macrophages, where the mycobacteria replicate exponentially. The primary site of infection in the lungs is called the Ghon Focus . Bacteria are picked up by Dendritic Cells , which can transport the bacilli to local (mediastinal) Lymph Node s, and then through the bloodstream to the more distant tissues and organs where TB disease could potentially develop: lung apices, peripheral lymph nodes, kidneys, brain, and bone.

Tuberculosis is classed as one of the granulomatous inflammatory conditions. Macrophages , T Lymphocytes , B Lymphocytes and Fibroblasts are among the cells that aggregate to form a Granuloma , with lymphocytes surrounding infected macrophages. The granuloma functions not only to prevent dissemination of the mycobacteria, but also provides a local environment for communication of cells of the immune system. Within the granuloma, T lymphocytes (CD4+) secrete a Cytokine such as Interferon Gamma , which activates macrophages to destroy the bacteria with which they are infected, making them better able to fight infection. T lymphocytes (CD8+) can also directly kill infected cells.

Importantly, bacteria are not eliminated with the granuloma, but can become dormant, resulting in a latent infection. Latent infection can be diagnosed only by tuberculin skin test, which yields a delayed hypersensitivity type response to purified protein derivatives of M. tuberculosis in an infected person.

Another feature of the Granuloma s of human tuberculosis is the development of cell death, also called necrosis, in the center of tubercles. To the naked eye this has the texture of soft white cheese and was termed Caseous Necrosis .

If TB bacteria gain entry to the blood stream from an area of tissue damage they spread through the body and set up myriad foci of infection, all appearing as tiny white tubercles in the tissues. This is called Miliary Tuberculosis and has a high case fatality.

In many patients the infection waxes and wanes. Tissue destruction and necrosis are balanced by healing and Fibrosis . Affected tissue is replaced by scarring and cavities filled with cheese-like white necrotic material. During active disease, some of these cavities are in continuity with the air passages Bronchi . This material may therefore be coughed up. It contains living bacteria and can pass on infection.

Treatment with appropriate Antibiotic s kills bacteria and allows healing to take place. Affected areas are eventually replaced by scar tissue.


Progression

In those people in whom TB bacilli overcome the immune system defenses and begin to multiply, there is progression from TB infection to TB disease. This may occur soon after infection (primary TB disease – 1 to 5%) or many years after infection (post primary TB, secondary TB, reactivation TB disease of dormant bacilli – 5 to 9%). The risk of reactivation increases with immune compromise, such as that caused by infection with HIV. In patients co-infected with M. tuberculosis and HIV, the risk of reactivation increases to 10% per year, while in immune competent individuals, the risk is between 5 and 10% in a lifetime.

About five percent of infected persons will develop TB disease in the first two years, and another five percent will develop disease later in life. In other words, about 10% of infected persons with normal immune systems will develop TB disease in their lifetime.

Some medical conditions increase the risk of progression to TB disease. In HIV infected persons with TB infection, the risk increases to 10% each year instead of 10% over a lifetime. Other such conditions include drug injection (mainly because of the life style of IV Drug users), substance abuse, recent TB infection (within two years) or history of inadequately treated TB, chest X-ray suggestive of previous TB (fibrotic lesions and nodules), diabetes mellitus, silicosis, prolonged corticosteroid therapy and other immunosuppressive therapy, head and neck cancers, hematologic and reticuloendothelial diseases (leukemia and Hodgkin's disease), end-stage renal disease, intestinal bypass or gastrectomy, chronic malabsorption syndromes, or low body weight (10% or more below the ideal).

Some drugs, including rheumatoid arthritis drugs that work by blocking Tumor Necrosis Factor-alpha (an inflammation-causing cytokine), raise the risk of causing a latent infection to become active due to the importance of this cytokine in the immune defense against TB.


Symptoms

TB disease most commonly affects the lungs (75% or more), where it is called pulmonary TB. Symptoms may include a productive, prolonged cough of more than three weeks duration, chest pain, and Hemoptysis . Systemic symptoms include fever, chills, night sweats, appetite loss, weight loss, and easy fatigability. The term consumption arose because sufferers appeared as if they were "consumed" from within by the disease. People from Asian and African descent may have lymph node TB more often than Caucasians.

Only 10 percent of TB infection progress to active TB disease; 90 percent have latent TB infection (LTBI) and have no symptoms.

Extrapulmonary sites include the pleura, central nervous system ( Meningitis ), lymphatic system ( Scrofula of the neck), genitourinary system, and bones and joints ( Pott's Disease of the spine). An especially serious form is "disseminated", or "miliary" TB, so named because the lung lesions so-formed resemble millet seeds on x-ray. These are more common in immunosuppressed persons and in young children. Pulmonary TB may co-exist with extrapulmonary TB.


Drug resistance

Drug-resistant TB is transmitted in the same way as regular TB. Primary resistance develops in persons initially infected with resistant organisms. Secondary resistance (acquired resistance) may develop during TB therapy due to inadequate treatment regimen, i.e. not taking the prescribed regimen appropriately or using low quality medication.


DIAGNOSIS

A complete medical evaluation for TB includes a medical history, a physical examination, a tuberculin skin test, a serological test, a chest X-ray, and microbiologic smears and cultures. The measurement of a positive skin test depends upon the person's risk factors for progression of TB infection to TB disease.
Bacteriophage-based assays are among a few new testing procedures that offer the hope of cheap, fast and accurate TB testing for the impoverished countries that need it most.
See: Tuberculosis Diagnosis , Tuberculosis Radiology



TREATMENT

For all practical purposes, only patients with tuberculosis of the lungs can spread TB to other people. People may become infected with TB but not have active disease: such people are said to have latent TB infection (LTBI) and are not capable of passing the infection on to other people. The reason for treating people with LTBI is to prevent them from progressing to active TB disease later in life (approximately 10% lifetime risk). The distinction is important because treatment options are different for the two groups.
See: Tuberculosis Treatment



PREVENTION OF TUBERCULOSIS

Prevention and control efforts include three priority strategies:

In tropical areas where the incidence of atypical mycobacteria is high, exposure to Nontuberculous Mycobacteria gives some protection against TB.


BCG vaccine

Many countries use BCG vaccine as part of their TB control programs, especially for infants. The protective efficacy of BCG for preventing serious forms of TB (e.g. Meningitis ) in children is high (greater than 80%). However, the protective efficacy for preventing pulmonary TB in adolescents and adults is variable, from 0 to 80%. In the United Kingdom , children aged 10-14 were typically immunized during school until 2005. (Routine BCG vaccination was stopped as it was no longer cost-effective. The incidence of TB in people born in the UK, and with parents and grandparents who were born in the UK, was at an all time low, and falling. Others continue to be offered BCG vaccination.)

The effectiveness of BCG is much lower in areas where mycobacteria are less Prevalent . In the USA, BCG vaccine is not routinely recommended except for selected persons who meet specific criteria:


Tuberculosis vaccine

The first Recombinant tuberculosis Vaccine entered Clinical Trial s in the United States in 2004 sponsored by the National Institute Of Allergy And Infectious Diseases (NIAID).
{Link without Title}

A 2005 study showed that a DNA TB vaccine given with conventional Chemotherapy can accelerate the disappearance of bacteria as well as protecting against re-infection in mice; it may take four to five years to be available in humans. PMID 15690060.

Because of the limitations of current vaccines, researchers and policymakers are promoting new economic models of vaccine development including prizes, tax incentives and Advance Market Commitments .


ANIMALS

Tuberculosis can be carried by many Mammal s. Domesticated species, such as cats and dogs, are generally free of tuberculosis, but wild animals may be carriers. As a result, many places have regulations restricting the ownership of Novelty Pet s, possibly including such partially domesticated species as Pet Skunk s; for example, the American state of California forbids the ownership of pet Gerbil s. The strictness of such restrictions generally depends on the Public Health policies adopted for fighting tuberculosis.

An effort to eradicate bovine tuberculosis from the cattle and deer herds of New Zealand is underway. It has been found that herd infection is more likely in areas where infected Vector Species such as Australian Brush-tailed Possums come into contact with Domestic Livestock at farm/bush borders. Controlling the vectors through possum eradication and monitoring the level of disease in livestock herds through regular surveillance are seen as a "two-pronged" approach to ridding New Zealand of the disease.

In both the Republic Of Ireland and Northern Ireland , Badger s have been identified as a vector species for the transmission of bovine tuberculosis. As a result, the government in both regions has mounted an active campaign of eradication of the species in an effort to reduce the incidence of the disease. Badgers have been culled primarily by snaring and gassing. It remains a contentious issue, with proponents and opponents of the scheme citing their own studies to support their position. [http://news.bbc.co.uk/1/hi/northern_ireland/4044897.stm [http://www.badger-killers.co.uk/Ireland/Ireland_news.html]


HISTORY

Tuberculosis has been present in humans since Antiquity , as the origins of the disease are in the first domestication of cattle (which also gave humanity viral poxes). Skeletal remains show prehistoric humans (4000 BCE) had TB and tubercular decay has been found in the spines of Egyptian Mummies from 3000-2400 BCE. There were references to TB in India around 2000 BCE, and indications of lung scarring identical to that of modern-day TB sufferers in preserved bodies (such as mummies) suggests that TB was present in The Americas from about 2000 BCE.

Phthisis is a Greek term for consumption. Around 460 BCE, Hippocrates identified phthisis as the most widespread disease of the times which was almost always fatal.

During the Industrial Revolution, tuberculosis was more commonly thought of as Vampirism . When one member of a family died from it, the other members that were infected would lose their health slowly. People believed that the cause of this was the original victim draining the life from the other family members. To cure this, people would dig up the body of what they thought was the vampire, open the chest and burn the heart, sometimes with the rest of the body. Furthermore, people who had TB exhibited symptoms similar to what people considered to be vampire traits. People with TB often had symptoms such as red, swollen eyes (which also creates a sensitivity to bright light), pale skin and coughing blood (which people often thought needed to be replenished, so they figured the only way for the afflicted to get blood back was by sucking blood). This may be how much of the common mythology of the vampire originated.

Although it was established that the pulmonary form was associated with 'tubercles' by . During the years 1838-1845, Dr. John Croghan, the owner of Mammoth Cave , brought a number of tuberculosis sufferers into the cave in the hope of curing the disease with the constant temperature and purity of the cave air. The first TB Sanatorium opened in 1859 in Poland , with another opening in the United States in 1885.

The bacillus-causing tuberculosis, ''Mycobacterium tuberculosis'', was identified and described on March 24 , 1882 by Robert Koch . He received the Nobel Prize In Physiology Or Medicine in 1905 for this discovery. Koch did not believe that bovine (cattle) and human tuberculosis were similar, which held back the recognition of infected milk as a source of infection. Later, this source was eliminated by the Pasteurization process. Koch announced a Glycerine extract of the tubercle bacilli as a "remedy" for tuberculosis in 1890, calling it 'tuberculin'. It was not effective, but was later adapted by Von Pirquet in a test for pre-symptomatic tuberculosis.

The first genuine success in immunizing against tuberculosis developed from attenuated bovine-strain tuberculosis by Albert Calmette and Camille Guerin in 1906. It was called 'BCG' ( Bacillus Of Calmette And Guerin ). The BGG vaccine was first used on humans on July 18 , 1921 in France , although national arrogance prevented its widespread use in either the USA , Great Britain , or Germany until after World War II .

Tuberculosis caused the most widespread public concern in the 19th and early 20th centuries as the Endemic disease of the urban poor. In 1815, one in four deaths in England was of consumption; by 1918 one in six deaths in France were still caused by TB. After the establishment in the 1880s that the disease was contagious, TB was made a Notifiable Disease in Britain; there were campaigns to stop spitting in public places, and the infected poor were "encouraged" to enter Sanatoria that rather resembled prisons. Whatever the purported benefits of the fresh air and labor in the sanatoria, 75% of those who entered were dead within five years (1908).

The promotion of Christmas Seals was started in 1904 in Denmark as a way to raise money for tuberculosis programs. It expanded to the United States and Canada in 1907-08 to help the National Tuberculosis Association (later called the American Lung Association ).

In the United States, concern about the spread of tuberculosis played a role in the movement to prohibit public spitting except into Spittoon s.

In Europe, deaths from TB fell from 500 out of 100,000 in 1850 to 50 out of 100,000 by 1950. Improvements in public health were reducing tuberculosis even before the arrival of antibiotics, although the disease's significance was still such that when the Medical Research Council was formed in Britain in 1913 its first project was tuberculosis.

It was not until 1946 with the development of the antibiotic Streptomycin that treatment rather than prevention became a possibility. Prior to then only surgical intervention was possible as supposed treatment (other than sanatoria), including the pneumothorax technique: collapsing an infected lung to "rest" it and allow lesions to heal, which was an accomplished technique but was of little benefit and was discontinued after 1946.

Hopes that the disease could be completely eliminated have been dashed since the rise of Drug-resistant strains in the 1980s. For example, Tuberculosis cases in Britain, numbering around 50,000 in 1955, had fallen to around 5,500 in 1987, but in 2000 there were over 7,000 confirmed cases. Due to the elimination of public health facilities in New York in the 1970s, there was a resurgence in the 1980s. The number of those failing to complete their course of drugs was very high. NY had to cope with more than 20,000 "unnecessary" TB-patients with many multi-drug resistant strains (i.e., resistant to, at least, both Rifampin and Isoniazid). The resurgence of tuberculosis resulted in the declaration of a global health emergency by the World Health Organization in 1993.


TUBERCULOSIS IN ART, LITERATURE, HISTORY AND FILM


Historical people

Due to the high prevalence of tuberculosis in the pre-antibiotic era, many historically prominent people developed or died from the condition, often in the prime of their productive period.

Theology:

Music:

Literature and poetry:

Military:

Paintings:

Others:


Portrayals

It has been speculated that the real-life ubiquity of illness and death due to tuberculosis affected the portrayal of these issues in European art and literature as well as history. The pale, "haunted" appearance of tuberculosis sufferers was fashionable at times, and has been seen as an influence on the works of Edgar Allan Poe who lost loved ones to this very disease. In recent years, this aesthetic has been revived by the " Goth " subculture.

Opera and theatre:

Novels:



Music:

Computer games:


SEE ALSO



REFERENCES



EXTERNAL LINKS

Organizations

Other