TB: Common yet fatally infectious

By

Dr Hjh Salizawati bt Mohd Zainal,

Senior Medical Officer,

National Tuberculosis Coordinating Centre, Kiarong

A boy pouring water as villagers collect their own from a lake in the village of Thamada, Myanmar. In 2006, there were 9.2 million new cases of symptomatic tuberculosis and three million deaths from the disease. AFP

Introduction
Tuberculosis or TB (short for tubercle bacillus) is a common yet dangerous infectious disease caused by airborne mycobacterium tuberculosis.

The disease has been a serious public health problem and in the early 19th century, the disease caused more than 30 per cent of all deaths in Europe.

With the advent of anti-tuberculosis drugs in the late 1940s, the battle against tuberculosis seemed to be won.

Unfortunately, in the 1990s, the world faced another threat against tuberculosis with the emergence of drug resistance tuberculosis, the escalation of HIV/AIDs rates, extreme poverty in many parts of the world and hence tuberculosis continues to be a deadly disease worldwide.

In 2006, there were 9.2 million new cases of symptomatic tuberculosis and three million deaths from the disease. And of the 9.2 million new cases, about three million occurred in Africa, three million in Southeast Asia, and about two million in Western Pacific region.
India and China reported the largest total number of new cases, but South Africa had the highest rate of new cases in the world, with 940 new cases per 100,000 people.

In Brunei Darussalam, it was reported in 2008 that there were 223 cases of TB where majority are pulmonary TB.

How Infection Develops
People can be infected with tuberculosis only from a person who has active disease.
The bacteria are spread almost exclusively through the air.

People with active tuberculosis in their lungs often contaminate the air with bacteria when they cough, sneeze, or even speak.

These bacteria can stay in the air for several hours. If another person breathes them in, that person may become infected. Thus, people who have contact with a person who has active tuberculosis (such as family members or health care practitioners who treat such a person) are at increased risk of getting the infection.

In most cases, tuberculosis bacteria that enter the lungs are immediately killed by the body's defences.

Those that survive are engulfed by white blood cells. The engulfed bacteria can remain alive inside these cells in a dormant state for many years (this stage is called latent infection).

In 90-95 per cent of cases, the bacteria never cause any further problems, but in about five-10 per cent of infected people, they eventually start to multiply and cause active disease especially in a person with impaired immune system - for example elderly, person with HIV/AIDs, the use of corticisteroids, person with chronic disease such as diabetes.
Tuberculosis primarily affects the lungs (80 per cent) but can also affect other parts of the body like the bones, skin, lymph nodes, gastrointestinal system and other organs.

Symptoms & Complications

Prolonged cough more than two-three weeks, is the most common symptoms of tuberculosis especially pulmonary tuberculosis.

The cough may produce a small amount of green or yellow sputum in the morning.
Eventually, the sputum may be streaked with blood.

Rapidly developing shortness of breath plus chest pain may also be symptoms of pulmonary tuberculosis.

People may awaken in the night and be drenched with a cold sweat, with or without fever.
People also feel generally unwell, with decrease energy and appetite. Weight loss often occurs.

Diagnosis
When people have symptoms that suggest tuberculosis, the following may be done: Chest x-ray; tuberculin skin test; blood tests; and microscopic examination and culture of sputum sample and other suspected specimens.

The sputum and other suspected specimens are examined under the microscope to look for tuberculosis bacteria and are used to grow bacteria in a culture.

Microscopic examination provides results much faster than a culture but is less accurate. It detects only half the cases of tuberculosis identified by culture.

However, traditional cultures do not provide results for many weeks because tuberculosis bacteria grow slowly. For this reason, treatment of people who may have tuberculosis is often begun while doctors wait for results of culture.

Treatment

People who are diagnosed with active tuberculosis are required to take medications to kill the bacteria.

The most commonly used anti-TB treatment are isoniazid, rifampicin, pyrazinamide and ethambutol which are taken orally.

Streptomycin is sometimes added to the regimen.

All of these drugs have side effects, but 95 per cent of people with tuberculosis are cured and do not experience any serious side effects. Because tuberculosis bacteria are very slow-growing, anti-tuberculosis treatment must be taken for a long time - usually six months (the first two months, four different types of anti-TB treatment are taken daily followed by continuation phase, two different types of anti-TB treatment are taken thrice weekly).

To avoid poor compliance, the World Health Organisation (WHO) has recommended implementation of DOTS.

What is DOTS?
DOTS or Directly Observed Treatment Short-Course has been the internationally recommended strategy to control TB since the early 1990s.

DOTS aims to decrease TB-related morbidity, prevent TB deaths, decrease TB transmission and avoid the development of drug-resistant TB.

Patients undergoing DOTS therapy will be observed by a medical professional or a trained supervisor while they take medication.

This ensures that the correct dosage of the drug is taken at the right time and also to be certain that patients do not vanish partway through treatment.

There are five elements of DOTS:
- Political commitment with increased and sustained financing;
- Case detection through quality-assured bacteriology;
- Standardised treatment with supervision and patient support;
- An effective drug supply and management system, and;
- A monitoring and evaluation system, impact measurement span.

Since 2000, Brunei Darussalam has implemented DOTS and the DOTS coverage has been 100 per cent in all the four districts. Each health centre has a trained DOTS medical personnel to supervise patients with tuberculosis while taking their anti-TB treatment.

Prevention
There are two aspects of prevention of TB: stopping the spread of infection; and treating early infection before it becomes active disease.

Stopping the spread of infection

Allowing good ventilation with fresh air will lower the concentration of bacteria and limits their spread. Also, allowing sunlight to enter houses can kill airborne tuberculosis bacteria.

Visitors visiting TB patients in the ward should wear masks to prevent them from getting infected by the bacteria.

Healthcare workers who handle samples of infected tissue or interact with people who may be infected with TB should also wear masks to help protect them.

People with active tuberculosis especially those with pulmonary TB need to be isolated such as in isolated ward, to reduce the spread of the airborne tuberculosis bacteria and they are also required to wear masks during isolation.

Treating early infection
People who have close contact with TB patients (especially pulmonary TB) will need to go for tuberculin skin test to find out whether they are infected with tuberculosis bacteria. And if they have positive tuberculin test (that is, latent TB infection), they should be treated with drugs that will prevent them from developing into active TB disease.

Isoniazid is very effective at stopping the infection before it becomes active disease. It is given daily for six to nine months.

Administration of BCG (Bacille Calmette-Guerin) vaccine at birth has been practiced in some countries especially in countries where the likelihood of contracting tuberculosis is high.

It is given to prevent development of serious complications among children, such as meningitis.

Conclusion
Tuberculosis is one of the oldest diseases known. In most countries, tuberculosis is stigmatised, and many people are reluctant to believe that they even have latent infection.
Individuals who have symptoms of TB are advised to seek for further examination at the nearest health centres.

Tuberculosis is curable but it can be fatal if left untreated.

Ministry of Health Public Awareness Programme

Source: Weekend, 9 May 2009

Now you see, Now you don't - Glaucoma, the silent blinding eye condition

By

Dept of Ophthalmology,

RIPAS Hospital

Blind Indonesian students playing chess inside their room at a rehabilitation centre in Jakarta, Indonesia. According to the World Health Organisation, more than 161 million people are visually impaired worldwide; among them some 124 million have low vision and about 37 million are blind. Another 153 million people suffer from visual impairment due to uncorrected refractive errors. More than 90 per cent of the world's visually impaired people live in low- and middle-income countries. The most common causes of blindness all over the world are cataract, glaucoma, cornea disorder, macula degeneration and diabetic retinopathy. epa

Courtesy of WHO

Glaucoma is a spectrum of related diseases. Increased pressure in the eye is a measurable problem in this disease. Increased pressure can occur due to a variety of reasons. When the pressure in the eye is high it can cause damage to the optic nerve, which transmits visual information from the eye to brain.

Glaucoma is the second most common cause of blindness worldwide, where 4.5 million persons globally are blind due to glaucoma and is expected to rise to 11.2 million by 2020. Up to 90 per cent of affected persons may not even aware of having the disease.

Glaucoma affects more than 4.5 million people worldwide of whom 10 per cent or 6.6 million people are blind. Glaucoma is the leading cause of irreversible blindness and is second only to cataract as the most common cause of blindness.

The prevalence of glaucoma in Southeast Asia (Singapore) is 4.7 per cent. No population-based data of glaucoma prevalence in Brunei Darussalam is currently available. However, extrapolating the prevalence in the region, about 13,000 should have glaucoma. But studies have shown that 50 per cent of glaucoma remains undiagnosed and at least 10 per cent of the people are blind in one eye at the time of diagnosis .It is commonly seen after 40 years of age and the chance of getting the disease increases with advancing age.

The inheritance of glaucoma still remains obscure. Family history of glaucoma can be seen in 50 per cent of the relatives in one kind of glaucoma. Trauma to the eye can also cause glaucoma.

There are certain groups of people who have increased risk of developing glaucoma; people with diabetes, myopia (short-sightedness), old age, small eyes, family history of glaucoma, migraine, high blood pressure and severe acute low blood pressure. These high-risk people should be evaluated early at the age of 40 and at regular intervals thereafter.

The fluid inside the eye is called the aqueous humor, which is formed by specialised cells. This fluid maintains the pressure normally up to 21mm Hg in normal eyes. This fluid is necessary to carry the nutrients to important structures and removes waste products. The fluid moves out of the eye through small channels to the blood circulation. When the normal flow of the fluid gets blocked the pressure inside the eye can build up causing damage to the optic nerve.

Damage to the optic nerve can cause blind areas in the outer side of vision, which is the beginning of the damage. As the disease gets worse only the central tunnel of vision remains. What is common to all glaucoma is the visual loss that cannot be reversed. Hence early diagnosis and management is very important.

There are two types of glaucoma - open angle and closed angle. In open angle glaucoma the normal drainage channels of the eye is anatomically open but does not function normally. When the fluid cannot leave the eye, the pressure builds up and eventually causes vision damage. This causes painless, progressive loss of vision that may escape the patient's attention. In angle closure glaucoma the site from which the fluid leaves the eye is narrow or physically blocked. This can occur suddenly, which causes a painful red eye with general symptoms such as vomiting. This is due to a rapid increase in eye pressure.

The cornerstone of management of glaucoma is detecting it at the earliest possible stage. People at risk should undergo annual eye examinations. The diagnosis of the problem is made by a comprehensive eye examination with special attention in estimating eye pressure, estimating field of vision and evaluation of the eye's optic nerve and visualising the drainage angle.

The eye pressure is measured by instruments called a tonometer. This can be non-contact where a jet of air is used to estimate the pressure or contact, where the doctor uses a special instrument, which touches the eye to measure the pressure. The latter is more accurate. The upper limit of eye pressure is set at 21mm of Hg. If the pressure is more than this on three consecutive separate visits, the suspicion of glaucoma arises. At times the doctor will estimate pressure at various times of the day to confirm that the pressures are elevated.

The optic nerve is assessed by examining the back of the eye with special lenses and a microscope. Increased pressure damages the nerve fibres, which can cause excavation of the optic nerve seen clinically as cupping, signifying the cumulative damage of individual nerve fibres. These changes are now recorded with digital cameras and archived for reference at subsequent assessment to monitor progression. There are many modern instruments such as optical coherence tomogram, nerve fibre layer analyser, which can exactly quantify the glaucomatous damage to the optic nerve.

The field of vision is estimated with a perimeter. The exact site and amount of the defect is measured with computer-assisted programmes and stored for comparison overtime.

The 'triad' of increased pressure, nerve damage and the loss of fields form the syndrome of glaucoma. At times only the eye pressure is elevated without associated corresponding changes in the field of vision or nerve changes. This is known as ocular hypertension and is such that a person's eyes need careful follow up examinations. Diagnosis of glaucoma is made if at least two of these three criteria are present.

The primary aim of treatment is to preserve the existing vision for as long as possible. The typical first line of treatment is the use of eye drops, which lowers the eye pressure by helping the fluid leave the eye or by reducing the amount of fluid produced in the eye. Some people need to take different combinations of eye drops depending on the extent of damage. The drops have to be applied as prescribed by the doctor paying attention to the time schedule. The eye medications do not cure the disease. They lower the pressure to prevent further damage and therefore must be used

continuously to maintain the pressure at a level, which has been decided by the doctor, much like medications to lower blood pressure in hypertension.
In addition there are laser treatments for both open angle and angle closure glaucoma. laser trabeculoplasty is generally done for open angle glaucoma that continues to progress despite use of medications. A laser beam is directed at the outflow channels to increase the fluid drainage. The procedure is done as an out patient procedure at the eye doctor's office. Laser treatment does not cure glaucoma. It helps to lower the eye pressure, which can either stop or slow down vision loss. Laser treatment is also done for angle closure glaucoma. This is called as laser iridotomy, which is done to eliminate the mechanical blockage by diverting the fluid. A small opening is made in the iris (the coloured part of the eye). The iris falls back to open the angles thereby removing the mechanical blockage to fluid egress resulting in lowered pressure.

All laser procedures have some risks and are not done unless the benefits outweigh the risks.

Source: Weekend, 25 April 2009