Multi-drug resistant TB (MDRTB)

Resistance to at least isoniazid and rifampicin (whether or not resistant to other drugs) is classified as multi-drug resistant. MDRTB is rare in Australia, remaining at less than two per cent per year in the past 15 years. There is, however, a potential risk of MDRTB in Victoria as most of the patients notified each year are over seas born from countries with high rates of drug resistance.

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Mantoux test

Hypersensitivity to tuberculin purified protein derivative (PPD) as demonstrated by the Mantoux test, follows after natural infection with M. Tuberculosis or BCG vaccination. In the general Victorian population, over 90 per cent of positive Mantoux tests are due to previous BCG vaccination. There are several other Mycobacteria besides M. Tuberculosis and exposure to any of these environmental Mycobacteria can give a positive result.

The Mantoux test is used:

• To detect latent infection in contacts of patients with tuberculosis.
• As a diagnostic aid.
• Prior to vaccination with BCG.

BCG

BCG (Bacille Calmette-Guerin) vaccine is a suspension of live, attenuated M. Bovis. The efficacy of BCG in adults is variable; it does not prevent pulmonary tuberculosis and it does not prevent TB infection. In children, it provides a greater degree of protection, especially in preventing the more serious forms of tuberculosis such as meningeal and miliary TB.

The National Health & Medical Research Council (NH&MRC) does not recommend BCG vaccination of the general Australian community where the risk of exposure to TB is low. BCG vaccination is only indicated for specific groups at high risk of TB. In Victoria, BCG vaccination of school children ceased in 1984.

For further information and recommendations see:

• Management, Control and Prevention of Tuberculosis Guidelines for Health Care Providers 2002-05
• The Australian Immunisation Procedures Handbook, 7th Edition, produced by NH&MRC and available at www.health.gov.au

Standards and control in relation to BCG vaccinators

Free BCG vaccine is available only to vaccinators authorised by the TB Program, Department of Human Services. Authorisation is through application to the TB Program. Currently, vaccinator information sessions are held twice a year.

Persons who are authorised vaccinators may order supplies of BCG from the Department of Human Services, telephone: (61 3) 1300 651 160.

Management of contacts of TB

Notification of TB by clinicians and laboratories is essential in the control of TB and allows identification of contacts to be made. Prompt notification is needed to initiate contact tracing in a timely fashion.

Contact tracing and surveillance is the responsibility of the Department of Human Services and is managed by the Department's TB Program. Anyone identified by health care workers as a contact of TB should be referred to the TB Program on 1300 882 008.

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Contact investigation

Contact investigation consists of:

• History taking
• Tuberculin testing
• Radiographic examination when appropriate.

The extent of investigation is governed by the characteristics of the source case. The scope of the investigation is extended when the following factors in the source case are present:

• AFB in sputum smear
• Cavitation on CXR
• Laryngeal TB
• Cough - particularly if productive of sputum

  and

• Where there is evidence of tuberculin conversion in any of the close contacts.

Following tuberculin testing, contacts can be grouped as:

• Initial negative reactors

  Tuberculin conversion takes a few weeks and may not have occurred yet in these contacts. Testing should be repeated in 8 to 12 weeks after a break of contact or in some cases, initial testing may be delayed for eight weeks.

• Initial positive reactors

  Initial positive reactors should be evaluated to exclude active disease. The positive tuberculin test may signify recent tuberculin conversion or an incidental finding.

Contacts identified by the TB Program as requiring further assessment are referred to specialist physicians for exclusion of active disease or consideration of treatment for latent infection.

The global situation

Tuberculosis occurs worldwide and had been decreasing steadily over past decades in developed countries. However this pattern has been reversed with the arrival of HIV and increased mobility of the world's population.

The World Health Organisation (WHO), estimated that one-third of the world population (about 1.7 billion people) is infected and globally, tuberculosis accounts for three million deaths annually, with 20 per cent of all deaths in adults in developing countries related to TB. Most of these will be from countries in Africa, Asia and parts of Latin America where TB is endemic and is the major cause of death due to an infectious disease. TB in HIV infected persons is more difficult to manage, runs a more fulminant course and has a high death rate. The WHO estimated that three million people worldwide had both HIV infection and active TB in 1990. HIV testing in several developing countries has shown that as many as 70 per cent of smear positive TB cases are also co-infected with HIV.

By global standards, Australia is managing well. The introduction of anti-TB drugs and a concerted public health campaign in the 1950s, as well as improved living standards, had a significant impact on the control of TB. The incidence of TB in Australia is amongst the lowest in the world with an annual incidence rate of around 6 per 100,000 population or between 900 and 1000 new cases each year. However, as two-thirds of the world's population who are infected with tuberculosis reside in Asia, this will have a significant impact on the control of TB in Australia as a result of increased immigration from these areas.

Over the years, the profile of TB in Australia has changed. We only see one to two cases of TB per 100,000 Australian born persons currently, in contrast to 50-100 times more cases in selected groups including people born overseas, aboriginal communities, the homeless and those with HIV infection.

Increased awareness amongst the medical profession with early diagnosis of TB, improved surveillance, screening of high risk groups and ensuring proper treatment of persons with active TB in order to minimise drug resistance, are part of the strategy for the control of TB in Australia.

Epidemiology of TB in Victoria

In Victoria, the incidence of TB has declined since the beginning of the century; cases of TB have dropped dramatically from over 1,000 cases in 1954 to 292 in 2000. However, over the last decade the rate of decline of notifications has reached a plateau, with an incidence rate over the last 5 years fluctuating between a low of 5.1/100,00 in 1998 and a high of 7.0/100,000 in 1999 (average 6.2/100,000).

However the epidemiology of TB in Victoria has changed significantly over the past 20 years, with the proportion of notified cases born overseas increasing from 37 per cent in 1970 to 86 per cent in 2000. The highest country-specific notification numbers come from the Vietnamese, Indian, Filipino and African born populations, reflecting the patterns of disease in their countries of birth. The focus of infection has also shifted from the young Australian born to the homeless and the aged. People older than 60 years account for one-quarter of the cases reported.

Of the overseas born patients, almost 50 per cent presented within five years and 30 per cent within two years of their arrival in Australia.

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Notification of Tuberculosis

Tuberculosis has been a notifiable disease in Victoria since 1889. Under the Health (Infectious Diseases) Regulations 2001, there is a statutory requirement for doctors who diagnose active tuberculosis and laboratories which isolate M. Tuberculosis from a biological specimen, to notify the Department of Human Services in writing, within seven days of confirmation of diagnosis.

For information about Notifications or a copy of the Notification form see Notifying Cases of Infectious Diseases within Victoria.

Further information

Further information can be obtained from the Tuberculosis Program, Department of Human Services, Communicable Diseases Section, telephone: (61 3) 1300 651 160.

See Management, Control and Prevention of Tuberculosis - Guidelines for Health Care Providers. This publication is also available in hard copy from the Department of Human Services Information Service, telephone: (61 3) 9096 7843.

Streeton, J. & Patel, A. 1989, Tuberculosis in Australia and New Zealand into the 1990s, National Health & Medical Research Council, Canberra.

Plant, A. J., Rushworth, R. L., Wang Q. & Thomas, M. 1991, 'Tuberculosis in New South Wales', Med J Aust, 154: pp. 86-89.

Reider, H. L, Cauthen, G. M, Comstock, G. W & Snider, D. E. Jr. 1989, 'Epidemiology of tuberculosis in the United States', Epidemiol Rev, 11: pp. 79-98.

Snider, D. E. Jr & Roper, W. L. 1992, 'The new tuberculosis', N Engl J Med, 326: pp. 703-5.

American Thoracic Society, Medical Section of the American Lung Association 1990, 'Diagnostic Standards and Classification of Tuberculosis', Am Rev Respir Dis, 142: pp. 725-735.

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