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Tuberculosis (TB)
Historically has been one of the world’s
worst killer diseases. Traces of TB have been found in skeletons of the late
Stone Age. (P01) show the death rate from tuberculosis in England and wales
from 1838 to 1970. It was one of the world’s great killer diseases in the
nineteenth century and was the largest signal cause of death in England and
wales during that time, accounting for one fifth of all death. By 1990, the
number of children dying from the disease has been reduced to less than 1 in 1
million in developed countries, nut at least 30million people worldwide still
sufficed symptoms, 95% of whom were living in developing countries. Up to 3
million a year are currently dying from TB, and up to one-third of the world’s
population carry the bacteria with no ill effects.
In the early 1990s the WHO declared the
disease a global emergency as case in the developed world, including Britain,
began to increase against and resistance to drugs began to grow. In 1992 there
were 5802 new cases in England. Worldwide, 8 million new cases are reported
every year. In 1993, Dr Kochi, manager of the WHO’s TB programme, said ‘TB is
out of control in many part of the world. The disease, which is preventable and
treatable, has been grossly neglected and no county is immune to it.’
The disease is caused by a fungus like
bacterium called Mycobacterium
tuberculosis, first discovered by Robert Koch in 1882. It is some time
referred to as the tubercle bacillus, bacilli being rod shaped bacteria. The
most common from in the UK is pulmonary TB which infects the lungs, although other
organs may be affected. Tow strains 0f the bacterium may cause the disease, the
human and bovine forms. The latter can be present in cattle and can enter the
milk of cow. It is very resistant and can remain alive for long period in milk
products. It is a very serious disease of cattle and has also been responsible
for a great deal of illness and death in human in the past, particularly in children.
Today, however, all milk in the UK is produced from cow that have been
‘tuberculin tested’, that is certified free of Mycobacterium. The milk also undergoes treatment at bottling plants
where it is subjected to pasteurization, sterilization or ultra high
temperature. These processes destroy at least 99% of all bacteria, including
all pathogens. Thus bovine tuberculosis is no longer of significance in humans.
Transmission, signs and
symptoms
Transmission
of pulmonary TB is by inhaling the bacteria into the lungs (droplet infection).
It is much less infectious than the common cold, and requires prolonged contact
between people. This account for the fact that it is associated with
overcrowded living condition, particularly where there is poor ventilation. The
bacterium can also resist drying out and can survive in the air and in house
dust for long periods. It is associated with poverty and bad housing where
people sleep several to a room. Refugee camps, dormitories for the homeless, and
prisoner of war camps are other situation in which it commonly spreads. In such
conditions, malnutrition and other infections resulting in a weakened immune
system can reduce resistance to the disease.
Tuberculosis can affect almost any tissue or
organ in the body, but disease of the lungs is by far the most frequent. It was
commonly known as ‘consumption’ in the past because it consumed the body,
causing it to waste away. The outcome of infection by tubercle bacilli depends
on a variety of factors. These include the age of the patient, the state of
nutrition (which is usually related to social class) and the presence or
absence of immunity. Immunity can be acquired by an individual as a result of a
previous mild infect or by vaccination.
The disease frequently shows
itself by vague symptoms such as loss of weight and excessive sweating. There
are often no symptoms in early tuberculosis and the disease may only be
accidentally discovered through a routing X-ray of the lungs. The diseases
start as an inflammation in one lung, which develops into a cavity. Then
further cavities develop, spreading into both lungs. As progressive destruction
of the lungs occurs the symptoms become more dramatic with coughing, appearance
of blood in the sputum, cheats pains, shortness of breath, fever and sweating,
poor appetite and weight loss.
Treatment and
prevention
Effective
medical treatment only began in 1947 with the introduction of the antibiotic
streptomycin. Mass vaccination did not begin in the Britain unit 1954. The
decline up to this point must have been due mainly to improving social
conditions, particularly improved housing. Vaccination accelerated the decline
and by 1970 the annual death rate in Britain had fallen to 1526.
Vaccination,
The development of an effective vaccine
against the disease resulted from the work of two French scientists, Alber
Calmette and Camille Guerin hence the names of the vaccine bacilli
calmette-Guerin (BCG). As far back as 1921 they developed attenuated (less
virulent) strains which were found to be effective for vaccination. Before
treating any individual it is important to check if they are already suffering
from TB or have recovered from it. The test is to puncture the skin with a
special instrument which has a ring of six short needles (the Heaf test). This
introduces a protein called tuberculin, purified from dead tubercle bacilli. In
the absence of past or present TB the skin show no reaction, but if an
individual has the disease or recovered, then the skin swells and reddens at
the injection site. This indicates a substantial immunity and no vaccine is
offered.
A detailed study of50000 healthy
children, reported on in 1963, showed that the incidence of the TB per 1000
children was 1.91 if unvaccinated, and 0.4 if vaccinated. The benefit of
vaccination therefore lasts for a long period of time because the children
still had immunity after more than ten years. Today children are vaccinated at
age twelve to fourteen years. Tuberculin tests indicate that about 10% of
children are positive at this age. These children are given a routine X-ray to
ensure that no active pulmonary tuberculosis is present, and very few children
have the disease.
Antibiotics,
A cure for
people already affected by TB did not come until 1943 when the antibiotic
streptomycin was discovered. The number of cases started to fall more rapidly
after this and continued to decline up to the mid 1980s, aided by the
introduction of further antibiotics such as rifampicin, isoniazid and others.
At that time
in western countries more than 80% of all active TB cases were of people over
sixty years of age.
Resurgence of the disease
After1980,
the demographics of the disease shifted in that more and more young people
between the age of the twenty five and thirty were developing that disease.
Between 1980 and 1986 five different surveys in the USA showed a relationship
between the rise of homelessness and surges of TB young adult populations. It
became clear by 1985 that new mutant strain of drug-resistant TB were also
present in the population. In 1986 patient with strains of Mycobacterium
resistant to both isoniazid and rifampicin numbered 0.5% of cases, by 1991 this
had resent to 3% and to 6.9% in 1994. The main contributing factors were
courses of treatment lasts 6-8 month and require consumption of at least three
or four antibiotics to reduce the chance of a strain multiplying which is
resistant to one of the antibiotics. The problem is made worse by the fact that
the patients starts to feel well again after a few weeks. Supervision by health
workers is difficult not only in developing countries, but also in large cities
such as new York where many sufferers are homeless, and where TB has become a
new epidemic.
From the beginning of the AIDS epidemic it
was noted that HIV positive member of the community developed a high rate of
tuberculosis. Many developing countries took steps to heed a WHO warning
regarding this relationship between HIV and TB. Doctors in the USA and most of Western
Europe, however, took little notice of these facts for they tended to view the
TB risk for HIV patent as the third world problem. In Africa TB began to spread
rapidly and HIV patent did not respond well to the two cheapest
antituberculosis drug, thiacetazone and streptomycin. By 1990 health experts in
some Africa countries were predicting defeat in their efforts to control tuberculosis.
The new strain of drug resistant bacteria
spread rapidly and there were clear interconnections between this new strains
and HIV. Patients with AIDS, with its immunodeficiency, were very susceptible
to infection, and death rates rose to 90-100% fatality. The percentage
increases in TB for different European countries are sown in table (02). These
are directly related to the increase in drug resistant strains and HIV
infection.
A reported in 1996 on TB in Edinburgh during
the period 1998-1992 showed the followings.
4.1%
increase in TB cases recorded among people over 65 years
12.6%
increase in TB cases recorded in younger patent.
In the
elderly, most cases were the result of reactivation of TB caught in childhood
or youth. The rise in both age groups was entirely due to the increased
resistance to antibiotics of the tubercle bacilli.
Immigration is also associated with an
increase in TB. For example areas in Britain with large immigrant population
have shown increase 25% higher than in the indigenous resident.
The world health organization has started
to achieve a more successful treatment of TB with its DOTS campaign (directly
observed treatment under the supervision). The patient is given pills under
supervision and watched each time to check the pills are swallowed. This is
done 0ver a period of 6 to 8 month and results in a cure of over 85% of cases.
po1
P2
Chest X-ray TB sufferer.
po1
P2
Chest X-ray TB sufferer.
