acute generalized *tuberculosis characterized by lesions in affected organs, which resemble millet seeds.
The weight loss and wasting associated with tuberculosis before treatment was available led to the disease’s popular name of consumption. Enlargement of the glands in the neck, formerly called scrofula, was known also as the ‘king’s evil’ from the supersition that a touch of the royal hand could cure the condition. Lupus vulgaris (see under LUPUS) is another of the skin manifestations of the disease.
The typical pathological change in tuberculosis involves the formation of clusters of cells called granulomas (see GRANULOMA) with death of the cells in the centre producing CASEATION.
It is estimated that there are 7–8 million new cases of tuberculosis worldwide each year, with 2–3 million deaths. The incidence of tuberculosis in developed countries has shown a steady decline throughout the 20th century, mainly as a result of improved nutrition and social conditions and accelerated by the development of antituberculous chemotherapy in the 1940s. Since the mid-1980s the decline has stopped, and incidence has even started to rise again in inner-city areas. In 2002, 7,239 cases of tuberculosis were noti?ed in the UK compared with 6,442 a decade earlier; more than 390 deaths in 2003 were attributed to the disease. Factors involved in this rise are immigration from higher-prevalence areas, poorer social conditions and homelessness in some urban centres and the association with HIV infection and drug abuse. The incidence of tuberculosis is also rising in many developing countries because of the emergence of resistant strains of the tubercle bacillus (see below). In the UK recently there have been serious outbreaks in a handful of urban-based schools.... tuberculosis
The symptoms depend upon the site of the infection. General symptoms such as fever, weight loss and night sweats are common. In the most common form of pulmonary tuberculosis, cough and blood-stained sputum (haemoptysis) are common symptoms.
The route of infection is most often by inhalation, although it can be by ingestion of products such as infected milk. The results of contact depend upon the extent of the exposure and the susceptibility of the individual. Around 30 per cent of those closely exposed to the organism will be infected, but most will contain the infection with no signi?cant clinical illness and only a minority will go on to develop clinical disease. Around 5 per cent of those infected will develop post-primary disease over the next two or three years. The rest are at risk of reactivation of the disease later, particularly if their resistance is reduced by associated disease, poor nutrition or immunosuppression. In developed countries around 5 per cent of those infected will reactivate their healed tuberculosis into a clinical problem.
Immunosuppressed patients such as those infected with HIV are at much greater risk of developing clinical tuberculosis on primary contact or from reactivation. This is a particular problem in many developing countries, where there is a high incidence of both HIV and tuberculosis.
Diagnosis This depends upon identi?cation of mycobacteria on direct staining of sputum or other secretions or tissue, and upon culture of the organism. Culture takes 4–6 weeks but is necessary for di?erentiation from other non-tuberculous mycobacteria and for drug-sensitivity testing. Newer techniques involving DNA ampli?cation by polymerase chain reaction (PCR) can detect small numbers of organisms and help with earlier diagnosis.
Treatment This can be preventative or curative. Important elements of prevention are adequate nutrition and social conditions, BCG vaccination (see IMMUNISATION), an adequate public-health programme for contact tracing, and chemoprophylaxis. Radiological screening with mass miniature radiography is no longer used.
Vaccination with an attenuated organism (BCG – Bacillus Calmette Guerin) is used in the United Kingdom and some other countries at 12–13 years, or earlier in high-risk groups. Some studies show 80 per cent protection against tuberculosis for ten years after vaccination.
Cases of open tuberculosis need to be identi?ed; their close contacts should be reviewed for evidence of disease. Adequate antibiotic chemotherapy removes the infective risk after around two weeks of treatment. Chemoprophylaxis – the use of antituberculous therapy in those without clinical disease – may be used in contacts who develop a strong reaction on tuberculin skin testing or those at high risk because of associated disease.
The major principles of antibiotic chemotherapy for tuberculosis are that a combination of drugs needs to be used, and that treatment needs to be continued for a prolonged period – usually six months. Use of single agents or interrupted courses leads to the development of drug resistance. Serious outbreaks of multiply resistant Mycobacterium tuberculosis have been seen mainly in AIDS units, where patients have greater susceptibility to the disease, but also in developing countries where maintenance of appropriate antibacterial therapy for six months or more can be di?cult.
Streptomycin was the ?rst useful agent identi?ed in 1944. The four drugs used most often now are RIFAMPICIN, ISONIAZID, PYRAZINAMIDE and ETHAMBUTOL. Three to four agents are used for the ?rst two months; then, when sensitivities are known and clinical response observed, two drugs, most often rifampicin and isoniazid, are continued for the rest of the course. Treatment is taken daily, although thrice-weekly, directly observed therapy is used when there is doubt about the patient’s compliance. All the antituberculous agents have a range of adverse effects that need to be monitored during treatment. Provided that the treatment is prescribed and taken appropriately, response to treatment is very good with cure of disease and very low relapse rates.... nature of the disease tuberculosis has
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