This site is intended for health professionals only

Tuberculosis resurfaces - a disease on the rise

Janet Gibson
RGN
Nurse Consultant
Communicable Disease Control Unit
Institute of Pathology
Newcastle General Hospital
Newcastle upon Tyne

There has been a rise in the number of tuberculosis (TB) cases in the UK in recent years, as well as the emergence of drug-resistant strains of TB. This article examines the facts about the disease, including occurrence, transmission, treatment and prevention. Basic facts about TB are summarised in Table 1.

[[NIP06_table1_45]]

Occurrence
Worldwide, tuberculosis (TB) mainly affects areas where poverty, malnutrition, poor housing and HIV prevail. In England and Wales there had been a steady decline in cases from the turn of last century that slowed in the 1960s. However, since 1987, numbers have risen from 5,798 to 6,087 notifications in 1998.(1) The greatest incidence is in urban areas, particularly London, among the homeless and within ethnic minorities, namely Africans, people from the Indian subcontinent and Afro-Caribbeans.(2) A cause of concern is the recent emergence of drug-resistant strains because of the limited number of alternative drugs available for treatment. Drug resistance has emerged due to noncompliance with treatment or inappropriate management.(3)

Tuberculosis
TB is an airborne disease caused by several species of mycobacteria: Mycobacterium tuberculosis, M. africanum and M. bovis. All can be transmitted by droplet infection. More rarely, TB can occur by ingesting food such as raw milk from infected dairy herds (M. bovis) or by direct inoculation through cuts in the skin.
When people inhale bacilli they can become infected. Tubercle bacilli multiply in alveolar macrophages, resulting in a small focus of inflammation. At this stage the immune response usually prevents the development of disease; therefore people are infected but asymptomatic and noninfectious. Latent infection can persist for a lifetime. About 10% of infected people will develop TB disease at some time in their lives.(4) The risk of progression to disease is higher for persons who are very young or old, HIV- positive or chronic alcohol misusers.(5)

Symptoms
People with TB may have some or all of the general symptoms of fatigue, fever, night sweats and weight loss. Other symptoms depend on the particular part of the body that is affected. For example, people with pulmonary TB may have a cough, which is often productive, or haemoptysis and chest pain, while those with laryngeal TB may experience hoarseness and ­difficulty in swallowing.

Diagnosis
Pulmonary disease accounts for two-thirds of TB cases. A chest X-ray can detect active disease. Sputum should be sent for microscopy and culture. Mycobacteria stain with special dyes and resist decolourisation with alcohol and acid washes, hence they are described as acid-fast bacilli (AFB). This is useful for diagnosis as mycobacteria grow very slowly and it can take weeks before a culture is available. In nonpulmonary TB, appropriate specimens (eg, a biopsy of the affected site) should be sent for microscopy and culture.
Children or adults who have not had the BCG can have a tuberculin skin test (Heaf or Mantoux). These tests react if the subject is either infected or has active disease. Some areas use tuberculin tests when a patient has had a BCG, but the results can be more difficult to interpret.

Infection control
Most people with TB are treated at home. Only those people with smear-positive pulmonary TB are considered infectious. They should be advised to cover their nose and mouth when they cough and to spit into tissues. They should also stay inside and avoid any public place, such as pubs, restaurants or public transport, until they complete two to three weeks of therapy. After this they are considered noninfectious.

Treatment
TB is treated with standard multidrug therapy, which is taken for some months, normally in two phases. Treatment is longer and more complex for TB meningitis and resistant strains. Only an experienced respiratory physician or paediatrician should manage the treatment of TB.
As already said, TB therapy is long and complex and requires compliance from the affected person. Compliance needs to be monitored through regular checks (eg, pill counts, urine tests, regular clinic attendance). When an individual is not compliant with therapy, directly observed therapy (DOT) should be considered. This involves the patient attending a day clinic or chest clinic where they can be observed taking their medication. Observation by primary care staff or other staff (eg, volunteers) could be undertaken in the patient's own home. People who have resistant TB, who misuse alcohol or who have a psychiatric illness should be automatically considered for DOT.(6)

Prevention
The Joint Tuberculosis Committee of the British Thoracic Society issued revised guidance on the control and prevention of TB in 2000 in the light of the changing epidemiology of the disease.(7)
All cases of TB under the Public Health (Control of Disease) Act 1984 are notifiable and should be reported to the proper officer, usually the Consultant in Communicable Disease Control (CCDC) in England and Wales or the equivalent in Scotland and Northern Ireland. The CCDC or respiratory physician will initiate case finding by the prompt identification and screening of contacts. About 10% of TB cases are found this way.(8)
Incidence rates of TB are high in many immigrants, refugees and asylum seekers. To identify those with TB it is national policy to screen new arrivals who plan to stay in the country for six months or more from high TB prevalence countries or situations, such as people displaced through war or famine.
In this country, children are vaccinated at 10-13 years of age with Bacillus Calmette­-Guerin (BCG), a live-attenuated vaccine derived from M. bovis. It has been shown to have an efficacy in protecting against TB in 70-80% of British schoolchildren.(9) Protection is thought to last at least 15 years. Children who have a positive reaction to a tuberculin skin test before BCG or as a diagnostic measure are prescribed chemotherapy with isoniazid to prevent reactivation in later life.

Conclusion
TB will be brought under control worldwide only if improvements in social conditions and healthcare are achieved. In the UK we need to be mindful of lessons learnt in recent times about TB management to ­prevent significant increases in TB.

References

  1. Public Health Laboratory Service. Tuberculosis - respiratory and non-­respiratory notifications, England and Wales, 1913-2000. Available from URL:http://www.phls.co.uk
  2. Rose AMC. 1998 national TB survey in England and Wales: final results. Thorax 1999;54 Suppl 3:A5.
  3. Wardman AG, et al. Tuberculosis: who should prescribe? BMJ 1982;284:569-71.
  4. US Department of Health and Human Services. Core curriculum on tuberculosis: what the clinician should know. Atlanta, Georgia: Public Health Services; 1994.
  5. The Interdepartmental Working Group on Tuberculosis. The prevention and control of tuberculosis in the United Kingdom: recommendations for the prevention and control of tuberculosis at local level. London: Department of Health; 1996.
  6. American Thoracic Society, medical section of the American Lung Association. Treatment of tuberculosis and tuberculosis infection in adults and children. Am J Respir Crit Care Med 1994;149:1359-74.
  7. Joint Tuberculosis Committee of the British Thoracic Society. Control and prevention of tuberculosis in the United Kingdom: code of practice 2000. Thorax 2000;55:887-901.
  8. Salisbury D, Begg NT, editors. Department of Health, Welsh Office, Scottish Office Department of Health, DHSS (Northern Ireland). 1996 ­immunisation against infectious disease. Edward Jenner Bicentenary edition. London: HMSO; 1996.
  9. Hussein SF, et al. Tuberculosis contact tracing: are the British Thoracic Society guidelines still appropriate? Thorax 1992;47:984-5.

Resources
Public Health Laboratory Service
W:www.phls.co.uk
Health Promotion England
W:www.hpe.org.uk
List of TB websites
W:www.cpmc.columbia.edu/tbcpp/extres.html