What You Need to Know About Tuberculosis

Submitted by SadInAmerica on Sun, 04/27/2008 - 2:11pm.

Tuberculosis (TB) has been claiming lives for millennia. Despite initial declines in the incidence of the disease in the mid-twentieth century, it is once again re-emerging.

War, famine, displacement and HIV all contribute to the increasing incidence of the disease among underprivileged individuals.

As TB is easily transmissible, any sudden surge in a given population should raise the alarm and prompt health officials to take action immediately.

Hippocrates was the first to identify tuberculosis in 460 BCE by the Greek name phthisis, describing it as a fatal disease accompanied by coughing up blood and fever.

In the year 1020 CE, the Iranian scholar Avicenna identified the contagious nature of pulmonary tuberculosis and introduced quarantine to limit its spread.

Due to the diversity of its symptoms, TB was not identified as a single disease until the 1820s. In 1839, J. L. Schonlein officially named the disease 'tuberculosis'.

Robert Koch received the Nobel Prize for isolating Mycobacterium tuberculosis, the pathogen responsible for the disease, in 1882.

Tuberculosis was considered the cause of 25 percent of the 19th century European deaths.

With the development of effective medication and the improvement of living conditions in the 20th century, the TB death toll witnessed a sharp plunge.

Today, although TB is found in almost every corner of the world, it is especially prevalent in sub-Saharan Africa and Southeast Asia. Western Europe and Scandinavia have the lowest prevalence.

According to the WHO 2008 Global tuberculosis report, over one-third of the world's population has been exposed to the tuberculosis pathogen with new infections occurring at a rate of one per second.

The data gathered from 202 out of 212 countries and territories in previous years indicates that some 8 million people fall victim to tuberculosis annually, resulting in approximately 2 million deaths.

In 2006, there were an estimated 9.2 million new tuberculosis cases and 1.5 million deaths; the disease was reported to be more prevalent in India and China, followed by Indonesia, South Africa and Nigeria.

Tuberculosis is a disease limited to the lungs in 75% of the cases; however, the infection can spread via the blood causing extra pulmonary involvements in the pleura, the central nervous system, the lymphatic system, the genitourinary system and the bones and joints.

It is noteworthy that not everyone infected develops the disease, i.e., the majority of cases experience asymptomatic or latent TB infection; subsequently one out of each 10 cases suffering from latent infections will develop active TB when the bacilli overcome the immune system.

Active pulmonary TB sufferers expel infectious droplets when they cough, sneeze or spit, putting others at risk of developing the disease.

The probability of transmission from one person to another is determined by the number of infectious droplets expelled by a carrier, the effectiveness of ventilation, the duration of exposure and the virulence of the mycobacterium tuberculosis strain.

In other words, prolonged, frequent or intense contact with an infected patient increases the risk of infection by 22%. Studies show an individual with active but untreated tuberculosis can infect 10-15 people per year.

Studies indicate that the number of people contracting TB due to a comprised immune system secondary to immunosuppressive drugs, substance abuse and HIV is rapidly increasing.

Poverty, malnutrition, poor general health, social disruption and living in areas where TB is common are other factors placing individuals at a higher TB risk.

Children exposed to high-risk adults and health care workers serving high-risk clients are also more prone to the disease.

The known factors which make individuals more susceptible to TB include smoking more than 20 cigarettes a day, diabetes mellitus, silicosis, head and neck cancers, hematologic and reticuloendothelial diseases (e.g. leukemia and Hodgkin), end-stage kidney disease, intestinal bypass or gastrectomy, chronic malabsorption syndromes and low body weight as well as recent TB infection or a history of inadequately treated TB.

 Systemic symptoms include fever, chills, night sweats, appetite loss, weight loss, pallor and fatigue. Pulmonary symptoms include chest pain, bloody sputum and a productive, prolonged cough for more than three weeks.

Identifying TB patients is an essential part of the global control program due to the difficulty in diagnosing tuberculosis, as it can mimic several diseases and it requires a long period to isolate the microorganism in the laboratory.

For the past 100 years, the diagnosis of tuberculosis has been made through purified protein derivative (PPD). In countries with a low TB incidence skin testing is considered a useful method.

It should be noted that the TB skin test is not accurate in areas where BCG vaccination has been widely performed, as the test result in immunized individuals or those with a past-cleared infection is identical to those currently in a state of infection.

Certain chest X-ray patterns can somewhat help identify suspicious cases; a microscopic examination and culture of the sputum sample can confirm the diagnosis.

New TB tests such as polymerase chain reaction (PCR) are also being developed with the hope of reaching a fast and more accurate diagnosis.

The development of the antibiotic streptomycin in 1946 made effective treatment possible. Today, rifampicin and isoniazid are the two most commonly used antibiotics.

An anti-tuberculosis regimen is comprised of taking multiple drugs for more than 6 months, the administration of which is often difficult for many patients.

Failing to complete the treatment course can lead to multi-drug resistant tuberculosis (MDR-TB) which is extremely difficult to treat.

As a result, WHO recommends a program known as DOTS (Direct Observed Therapy Short course) to help patients in need of medication-taking supervision.

TB prevention and control are parallel to each other; prevention depends on avoiding contact with active cases, using preventive medications in high-risk individuals, maintaining good living standards and vaccinating children. The control strategy consists of finding, isolating and treating carriers.

Vaccination significantly reduces the risk of pulmonary TB and prevents blood-borne cases such as miliary TB or tuberculosis meningitis, which can be difficult to diagnose and lead to various complications.

Although the first TB vaccine, BCG, was developed between 1905 and 1921, it was not widely used until World War II.

As the effectiveness of BCG is lower in countries where mycobacteria are less prevalent, the vaccine is only prescribed for the high-risk population in such areas.

Today, researchers are trying to develop several new vaccines with the aim of preventing TB infection, some of which have shown promising results.

In 1993, the World Health Organization declared TB a global health emergency. In 2000, in collaboration with some 500 organizations, WHO developed the Stop TB Partnership global plan with the aim of saving 14 million lives between 2006 and 2015.

The 2008 WHO report conceded that due to the delayed diagnosis of infected cases controlling the tuberculosis epidemic in 2006 had been faced with a slowdown.

According to the report, MDR-TB and the lethal combination of TB and HIV are the two main reasons for the slowed progress of the global plan.

The report shows that of the nine million new tuberculosis cases in 2006, almost 750,000 occurred in individuals suffering from HIV.

Many believe DOTS is the core of the stop TB strategy, as it has helped treat more than 22 million patients since its commencement.

The World TB Day, March 24, marks the day when Dr Robert Koch announced the discovery of the TB bacillus, the main cause of tuberculosis, in 1882.

The annual event aims to raise awareness about the health threat posed by tuberculosis, to inform people that TB does not mean death, familiarize them with effective treatments, and most importantly help individuals realize that by controlling HIV tuberculosis can be controlled.

Patricia Khashayar, MD., Press TV, Tehran - March 30, 2008 - posted at www.presstv.ir/


Multidrug-Resistant Tuberculosis

Division of Pulmonary and Critical Care Medicine, Department of Medicine, All India Institute of Medical Sciences, New Delhi 110 029, India. sksharma@aiims.ac.in

Multidrug-resistant tuberculosis (MDR-TB), caused by Mycobacterium tuberculosis that is resistant to both isoniazid and rifampicin with or without resistance to other drugs, is a phenomenon that is threatening to destabilize global tuberculosis (TB) control. MDR-TB is a worldwide problem, being present virtually in all countries that were surveyed. According to current World Health Organization and the International Union Against Tuberculosis and Lung Disease estimates, the median prevalence of MDR-TB has been 1.1% in newly diagnosed patients. The proportion, however, is considerably higher (median prevalence, 7%) in patients who have previously received anti-TB treatment. While host genetic factors may contribute to the development of MDR-TB, incomplete and inadequate treatment is the most important factor leading to its development, suggesting that it is often a man made tragedy. Efficiently run TB control programs based on a policy of directly observed treatment, short course (DOTS), are essential for preventing the emergence of MDR-TB. The management of MDR-TB is a challenge that should be undertaken by experienced clinicians at centers equipped with reliable laboratory services for mycobacterial cultures and in vitro sensitivity testing as it the requires prolonged use of costly second-line drugs with a significant potential for toxicity. The judicious use of drugs; supervised standardized treatment; focused clinical, radiologic, and bacteriologic follow-up; and surgery at the appropriate juncture are key factors in the successful management of these patients. With newer effective anti-TB drugs still a distant dream, innovative approaches such as DOTS-Plus are showing promise for the management of patients with MDR-TB under program conditions and appear to be a hope for future.

PMID: 16840411 [PubMed - indexed for MEDLINE]

posted at www.ncbi.nlm.nih.gov/pubmed/

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Submitted by SadInAmerica on Sun, 04/27/2008 - 2:11pm.