Tuberculosis
(Professor Guy Marks / Dr Claudia Dobler)

Tuberculosis (TB) causes a substantial burden of disease on a global scale but has received relatively little attention in Australia, largely due to the rapid decline in incidence and mortality in the 35 years between 1950 and 1985. However, since that time there has been little further decline in incidence and the disease remains endemic in migrants from high burden countries. The risk of progression to active disease is increased by states that impair immunity. Although severe immunodeficiency associated with HIV infection is relatively uncommon in Australia, lesser degrees of immunodeficiency, associated with advanced age, diabetes, chronic renal impairment are common. In fact, these conditions are relatively more common in Australia than in most countries with a high burden of TB infection. For example, dialysis and transplantation for patients with end-stage renal failure is relatively uncommon in Vietnam, hence the prevalence of end-stage renal failure is much lower than it is here. Migrants from Vietnam, China, India, Philippines and other high burden countries have a high prevalence of TB infection acquired prior to migration to Australia and, once in Australia, are at risk of chronic low-level immunodeficiency states such as diabetes, chronic renal failure and advanced age. The co-existence of these two states makes this group at particular risk of progressing to active tuberculosis. However, the actual risk of tuberculosis in association with these conditions is not known.

At Liverpool Hospital, Dr Claudia Dobler (CCRE Fellow), in conjunction with Professor Marks, has been examining the incidence of recurrent tuberculosis among patients treated for tuberculosis. This has involved collaboration with the NSW Department of Health (Communicable Diseases Branch) and the Centre for Microbiology at the ICPMR Westmead. We have shown that the rate of recurrence among patients treated in NSW is very low. Furthermore, a substantial proportion of those cases that do recur are, in fact, new infections. This research has important implications for the control of tuberculosis in low-to-intermediate prevalence settings and strongly supports the continuation of Directly Observed Therapy.

Dr Claudia Dobler is also assisting the conduct of a national database linkage project of people with diabetes and end-stage renal failure to quantify the incidence of tuberculosis in among people with these conditions. The relative risk of tuberculosis associated with diabetes and end-stage renal failure will be estimated along with the population-attributable fraction. This information will be used to advise clinicians treating migrants from high TB burden countries who have diabetes and/or end-stage renal failure about the value of screening for, and treating, TB infection to prevent progression to TB disease.

Professor Marks has run tuberculosis workshops for respiratory trainees. As a member of the NSW Department of Health Tuberculosis Advisory Committee he has participated in the formulation of Department of Health Policy Directives on TB control: including treatment of latent TB infection, TB control in migrants, and TB control in health care workers.