EDITORIAL T uberculosis in Immigrants to Canada A Global Problem Which Requires a Global Solution R obert L. Cowie, MD, MSc, FCP (SA) 1 S tephen K. Field, MD, CM, FRCPC 1 D onald A. Enarson, MD, FRCPC 2 T uberculosis has, for most of the 20th century, been on the decline in the industrial- ized world. At the same time, the disease has dramatically increased in the majority of the world’s population who live in the developing world. 1,2 Tuberculosis was declared a ‘global emergency’ by the World Health Organisation in 1993 at a time when many Western countries were talking about the impending elimination of the disease. The low level of concern about the disease that this engendered in the Western world con- tributed to the lack of progress in the development of new approaches and tools to control tuberculosis. 3 Also responsible was the unfounded confidence that the development in the 1970s of efficacious ‘short course’ treatment regimens would, given time, resolve the prob- lem of tuberculosis. The results of the few effectiveness studies using these regimens under program conditions failed to raise the alert that short-course regimens were not, in reality, having their desired effect. 4 For example, a 6-month regimen tested by the British Medical Research Council in East Africa, using subjects selected for compliance and treated largely in hospital, had a relapse rate of 9% 5 while under program conditions, the same regimen had a relapse rate of 25%. 4 The widespread introduction of these treatment regimens with- out an adequate infrastructure probably increased the infective pool by decreasing the mor- tality but not increasing the cure of tuberculosis. 6 Furthermore, the inappropriate use of antituberculosis drugs has progressively increased the prevalence of resistant strains of Mycobacterium tuberculosis. 6,7 Against the background of declining interest in and dismantling of programs for tuber- culosis in the industrialized countries, there has been a steady increase in emigration from high prevalence to low prevalence tuberculosis countries. 1 In areas in the industrialized world favoured by immigrants and where the matter has been studied, tuberculosis in foreign-born accounts for most of the disease. In Canada, 58% of all tuberculosis occurs in foreign-born 8 while in the southern part of the province of Alberta, foreign-born accounted for 17% of the population and 71% of the tuberculosis in the period 1990 to 1995. 9 In Canada it has been proposed that the population be supplemented with approximately 250,000 immigrants per year; this could lead to an annual increase rather than the hoped for decrease in the incidence of tuberculosis. Tuberculosis in foreign-born is often caused by Mycobacterium tuberculosis which is resis- tant to one or more of the conventional antituberculosis drugs. 10 Resistant Mycobacterium tuberculosis is three times more common in foreign-born than it is in Canadian-born with tuberculosis. 11 Disease caused by resistant Mycobacterium tuberculosis is more difficult to treat and has greater morbidity and mortality than disease caused by a susceptible organ- ism. 12 The Canadian preimmigration screening program emphasizes tuberculosis by including a history of past tuberculosis and, for all potential immigrants over 11 years of age, a chest x-ray. Those found to have active pulmonary tuberculosis are denied immigration until their disease has been proved to be inactive by adequate treatment and follow-up. Those judged to have inactive pulmonary tuber- culosis are required to attend for tubercu- losis assessment after their arrival in Canada. In a paper in this issue of the Journa l , Uppa l uri and coll ea gues f rom Ontario report that this surveillanc e process identified only 14% of the immi- grants who subsequently were diagnosed with tuberculosis. 13 Their finding is similar to that reported in a survey of tuberculosis in immigrants to sout h ern Alb erta i n which the immigration process identified 10% of those who subsequently developed tuberculosis. 9 In both of these reports, the impact of treatment of latent tuberculosis infection (chemoprophylaxis) was disap- pointing, pointing to poor compl ianc e either on the part of the physicians or the patients. Poor compl iance is t he major problem with chemoprophylaxis and may be particularly poor in foreign-born popu- lations. 14 The current guidelines suggest that all immigrants 35 years of age or less, wit h tubercul in reactions of 10 mm or greater, who come from high prevalence countries should be offered chemoprophy- laxis with isoniazid. 15 Half of the immi- grants, all from countries with a high inci- d ence of tuberculosis, who develo p e d tuberculosis in southern Alberta 9 and 60% of those in Canada 8 were under 35 years of age at the time of their arrival in Canada a n d mig h t t h us h ave b een e l igi bl e f o r chemoprophylaxis. Although the risk of isoniazid-induced liver toxicity increases significantly above the age of 35 years, 16 those bel ow that age, especiall y women and particularly those who are in the first year post-partum, may be at increased risk with four times more deaths than men of t he same age . 17 Severe side effects and death have been reported in recent reports, o ne from Canada associated wit h isoniazid 18 and another from the USA in association with a ‘short-course’ regimen with rifampin and pyrazinamide. 19 The data from follow-up of population groups in Canada demonstrate that isoniazi d chemoprophylaxis might cause more cases of serious side-effects or even deaths than the number of cases of tuberculosis pre- vented when used in those with a positive tuberculin test and no other risk factors for developing tuberculosis. 20 This opinion has previously been presented by others, 21 and is supported by the observation that the incidence of tuberculosis in the Canadian i mmi g rant population is only 20 pe r 1. Tuberculosis Services, Calgary Regional Health Authority, Department of Medicine, University of Calgary, Calgary, AB 2. International Union Against Tuberculosis and Lung Disease, Paris, France Correspondence: Dr. R.L. Cowie, Health Sciences Centre, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Tel: 403-220-8981, Fax: 403-270-8928, E-mail: cowie@ucalgary.ca MARCH – APRIL 2002 CANADIAN JOURNAL OF PUBLIC HEALTH 85