Prevalence and determinants of tuberculin reactivity among physicians in Edmonton, Canada: 1996-1997.

BACKGROUND: Health care workers (HCW) have historically borne a heavy burden of tuberculosis (TB) infection and disease. Unfortunately, physicians are rarely included in HCW surveys of tuberculin exposure and infection. METHODS: The prevalence and risk factors for tuberculin reactivity were determined for a sample of the 1732 licensed physicians in Edmonton. Stratified random sampling was used to select 554 specialists and 219 general practitioners. These physicians were contacted by means of an introductory letter and a follow-up telephone call to solicit participation. All eligible physicians were asked to complete a questionnaire and those with either no recorded positive tuberculin test or a previously negative result were two-step tuberculin skin tested. RESULTS: In total, 560 physicians (72.4 %) participated in the study. The overall tuberculin reactivity for this population was 45.9%. Using logistic regression analysis, we determined that risk factors for reactivity were aged over 45 years, of foreign-birth, previous Bacillus Calmette-Guérin (BCG) vaccination, foreign practice experience, and being a respiratory medicine specialist. CONCLUSION: The prevalence of tuberculin reactivity among physicians is considerably higher than estimates for the general Canadian population. This observed excess risk may be associated with factors linked to their medical practice. The high participation rate suggests physician willingness to participate in this type of research, and emphasizes the need to include them in routine HCW surveillance.

Linkage of tuberculosis to chromosome 2q35 loci, including NRAMP1, in a large aboriginal Canadian family.

An epidemic of tuberculosis occurred in a community of Aboriginal Canadians during the period 1987-89. Genetic and epidemiologic data were collected on an extended family from this community, and the evidence for linkage to NRAMP1, a candidate gene for susceptibility to mycobacterial diseases, was assessed. Individuals were grouped into risk (liability) classes based on vaccination, age, previous disease, and tuberculin skin-test results. Under the assumption of a dominant mode of inheritance and a relative risk of 10, which is associated with the high-risk genotypes, a maximum LOD score of 3.81 was observed for linkage between a tuberculosis-susceptibility locus and D2S424, which is located just distal to NRAMP1, in chromosome region 2q35. Significant linkage was also observed between a tuberculosis-susceptibility locus and a haplotype of 10 NRAMP1 intragenic variants. No linkage to the major histocompatibility-complex region on chromosome 6p was observed, despite distortion of transmission from one member of the oldest couple to their affected offspring. The ability to assign individuals to risk classes was crucial to the success of this study.

Observations on animal and human health during the outbreak of Mycobacterium bovis in game farm wapiti in Alberta.

This report describes and discusses the history, clinical, pathologic, epidemiologic, and human health aspects of an outbreak of Mycobacterium bovis infection in domestic wapiti in Alberta between 1990 and 1993, shortly after legislative changes allowing game farming. The extent and seriousness of the outbreak of M. bovis in wapiti in Alberta was not fully known at its onset. The clinical findings in the first recognized infected wapiti are presented and the postmortem records for the herd in which the animal resided are summarized. Epidemiologic findings from the subsequent field investigation are reviewed, the results of recognition and investigation of human exposure are updated, and recommendations for reduction of human exposure are presented.

Procedures for developing a simple scoring method based on unsophisticated criteria for screening children for tuberculosis.

OBJECTIVE: To develop a scoring system for screening children for tuberculosis (TB) and for selecting suspects for further investigation in tuberculosis control programmes. Application of the score model, which would not require sophisticated or expensive technology, would be directed towards resource-poor countries with high prevalences of tuberculosis, where health care workers have to deal with diagnostic problems away from district hospitals or diagnostic facilities. DESIGN: Based on contributions from members of an IUATLD task group from 10 countries on the use of diagnostic criteria in childhood tuberculosis, criteria were selected to be used as elements in a score model. Data were collected by standardised questionnaire on 879 subjects aged under 15 years. Of these, 794 were considered probable or confirmed cases of tuberculosis by the diagnosing doctors. From each record, the criteria/procedures used in the diagnosis of probable/confirmed TB and regarded by the doctors as relevant criteria were selected. Bacteriology, histology and chest radiography were used either singly or collectively as the definitive reference (gold standard) against which the more subjective criteria (symptoms, clinical signs, skin test) would be evaluated. The latter criteria cited as relevant were then ranked and further explored for inclusion in the score model. The relative importance of each criterion to every other criterion on the list was expressed as weights, determined by employing a logarithmic least squares method to solve the ratio scale estimation problem which underlies decision-making involving more than one criterion. The resultant values were then assigned to each criterion in the final score model. RESULTS: The five clinical criteria thought to be most relevant as predictors of disease in children were history of contact with a case of tuberculosis, positive skin test, persistent cough, low weight for age, and unexplained/prolonged fever. In selecting the optimal cut-off points for the model at which tuberculosis would be suspected, low sensitivity and specificity (below 70%) but reasonably good positive predictive values (60%-77%) were obtained, depending on age group and epidemiological setting. In low tuberculosis prevalence settings, heavy reliance is placed by the model on a history of contact with a household case of tuberculosis and on a positive skin test, both of which have to be true. For high prevalence settings, more or less equal weighting is assigned to all five elements. Case contact and skin tests are less important, with low body weight, prolonged fever and cough being more indicative of tuberculosis. CONCLUSION: The model provides for epidemiological differences between target populations and should prove successful as a screening tool to select children for further investigation by radiography and bacteriology.

Antituberculosis drug resistance in immigrants to Alberta, Canada, with tuberculosis, 1982-1994.

SETTING: Provincial Tuberculosis Service, Alberta, Canada. OBJECTIVE: To estimate resistance rates of Mycobacterium tuberculosis to antituberculosis drugs in relation to previous treatment, country of origin, age and duration of residence in Canada. DESIGN: Retrospective chart review of all culture-positive tuberculosis diagnosed between 1982 and 1994 in immigrants to Alberta. RESULTS: A total of 753 immigrants with culture-positive tuberculosis were studied; 131 patients (17.4%, 95% Confidence Interval [CI] 14.7, 20.1) had strains resistant to one or more of the first-line medications (isoniazid [INH], rifampin [RIF], ethambutol [EMB], pyrazinamide [PZA], and streptomycin [SM]). Initial and secondary resistance rates were 16.4% and 30.3%, respectively (P = 0.003, Odds ratio [OR] 2.2, 95% CI 1.3, 3.8). Resistance occurred in 22.2% of patients 40 years of age and under, and in 13.8% of those over 40 years of age (P = 0.005, OR 1.8, 95% CI 1.2, 2.6). Resistant M. tuberculosis was isolated from 20.4% of those who had lived in Canada for less than 15 years, and in 9.0% of those who had immigrated to Canada more than 15 years before diagnosis (P < 0.001; OR 2.4, 95% CI 1.3, 4.2). Resistance rates to individual medications in all immigrants were as follows: INH 9.9% (95% CI 7.8, 12.0), RIF 0.8% (95% CI 0.2, 1.4), EMB 1.9% (95% CI 1.0, 2.8), PZA 1.9% (95% CI 0.3, 3.5), and SM 12.9% (95% CI 10.4, 15.4). Immigrants from Vietnam, China, and the Philippines had tuberculosis strains that were resistant to one or more of the first line medications in 30.2%, 21.8%, and 15.5% of cases, respectively (P = 0.04). CONCLUSION: In industrialized countries such as Canada where most cases of tuberculosis are diagnosed among the foreign-born, drug resistance surveys continue to be an important part of an effective tuberculosis control program.

Tuberculosis among institutionalized elderly in Alberta, Canada.

Previous studies in the US have suggested that the risk of tuberculosis is increased among elderly residents of nursing homes. This registry-based study determined and compared the tuberculosis incidence rate for the elderly in nursing homes and community dwellings in Alberta, Canada, over the 5-year period 1979-1983. Rate ratios (RR) using the community elderly rate as baseline, were estimated for all notified cases and for culture positive cases only. Adjustment was made for the variables age, sex, and ethnicity. The nursing home elderly in Alberta did not have an increased risk of tuberculosis: adjusted RR = 1.09, 95% CI : 0.38-1.80.

Perinatally acquired neonatal tuberculosis: report of two cases.

Perinatally acquired neonatal tuberculosis occurs rarely, is difficult to diagnose, may be the indicator of untreated tuberculosis in the mother, and could result in nosocomial transmission to neonatal patients, visitors to neonatal intensive care units, and health care workers. The disease may be more common in certain ethnic and social groups. Neonatal mortality approaches 30%. We report two cases with different outcomes. A neonate was treated for clinical miliary tuberculosis and survived; Mycobacterium tuberculosis was cultured from bronchoscopic washings, maternal genital fluids, and tissues. A second infant died at age 46 days, and autopsy disclosed miliary tuberculosis of lungs, mediastinal and mesenteric nodes, liver, spleen, and bone marrow. The lungs were most severely affected, but the placenta and central nervous system were not involved. The histopathology was not granulomatous. After the diagnosis in the infant, the mother was ascertained to have pulmonary and genital tuberculosis. Fetal and neonatal tuberculosis could be acquired transplacentally as prenatal tuberculous chorioamnionitis, perinatally through aspiration and ingestion of infected maternal genital tissues and fluid, or postnatally through droplet spread from cases of active tuberculosis. These two neonates probably acquired the disease perinatally from maternal genital tuberculosis.

An epidemic of primary tuberculosis in a Canadian aboriginal community.

In 1987, an outbreak of primary tuberculosis occurred in a Canadian aboriginal community of 350 people. The source case was a young woman who had been symptomatic for four months with smear positive cavitary pulmonary tuberculosis. Her 17 siblings and their families were frequent close contacts. Among the 626 persons surveyed in the community and environs, 35 additional active cases of tuberculosis were identified. The mean age of cases was 13 years and the median age 10 years. The method of diagnosis was bacteriological in 20 and radiological in 16. There were 257 positive tuberculin reactors of whom 120 had no previous record of a positive skin test. Isoniazid prophylaxis was recommended to all new reactors, close household contacts, reactors under the age of 35 years and reactors with lung scars. One late case was identified at one year of follow-up in a contact who had refused prophylaxis. The rates of infection and disease were higher in the family (65% and 46%, respectively) than in the community and environs (19% and 5.6%, respectively). This report illustrates the nature of a point source epidemic of primary tuberculosis in a susceptible community with a predictable reservoir of infection. The delay in diagnosis of the source case allowed numerous new infections to occur. However, prompt aggressive contact follow-up was successful in containing the epidemic. To prevent future outbreaks, the reservoir of infected persons must be identified and administered chemoprophylaxis.

Antimicrobial prophylaxis for open heart operations.

Between 1986 and 1988, 450 adults undergoing coronary artery bypass, cardiac valve replacement, or both were enrolled into a prospective, randomized, comparative trial of cephalothin versus cefamandole as perioperative prophylaxis. They were assessed during their hospitalization and at 6 weeks and 6 months after discharge for postoperative infectious complications. Eleven patients had major postoperative infections including 5 with sternal wound infections (three bacteremic), 6 with bacteremia, 1 with prosthetic valve endocarditis, and 3 with severe venous donor graft site infections. Eight major infections occurred in patients receiving cephalothin prophylaxis and three in patients receiving cefamandole, with all five sternal wound infections occurring in the cephalothin group. Postoperative pathogens responsible for the major infections included gram-negative aerobes in 5 patients, Staphylococcus aureus in 4, and Staphylococcus epidermidis in 2. Preoperative colonizing staphylococcal isolates were not predictive of postoperative staphylococcal pathogens. Although there was no statistically significant difference in rate of major postoperative infectious complications using either cephalothin or cefamandole prophylaxis, there was a trend in favor of cefamandole. Gram-negative aerobes are becoming increasingly important pathogens in this setting.

Childhood lymphadenitis in a harsh northern climate due to atypical mycobacteria.

Between 1979 and 1983, 16 patients under 15 years of age living within 480 km of Edmonton, Alberta (latitude 53 degrees 34' N) were seen with cervical lymphadenitis caused by atypical mycobacteria. During this period only 4 cases of cervical lymphadenitis from Mycobacterium tuberculosis occurred in the same age and geographical grouping. Young children age 1-4 years accounted for most cases (14/16). The onset showed no seasonal preponderance and the nodal enlargement was either asymptomatic (8/16) or associated with only minor systemic symptoms. M. avium intracellulare scrofulaceum (6 cases) or M. avium intracellulare (4 cases) were identified on cultures from the infected node. In the remaining cases characteristic histopathology and acid fast bacilli were seen on biopsy specimens but no organisms could be cultured. Surgery was employed in all cases either for diagnosis or for therapy. This series demonstrates that atypical mycobacteria may cause childhood lymphadenitis throughout the year in a harsh inland Northern climate. The etiological pathogen can be difficult to culture but complete surgical excision of the infected node is usually curative.

South Australian kindergarten children: effects of fluoride tablets and fluoridated water on dental caries in primary teeth.

Dental examinations of approximately 5,000 kindergarten children each year over a seven-year period provided the data for a comparative study of the effects of fluoride tablets and fluoridated water on primary teeth. The lifetime use of fluoridated water resulted in caries-free teeth in 80 per cent of children aged 3-4 years, 67 per cent of those aged 4-5 years, and 55 per cent of those aged 5-6 years. After a lifetime use of daily fluoride tablets the percentages were 87, 74, and 72, respectively. When neither fluoridated water nor tablets were available, the percentages were 69, 49, and 41, respectively. Water fluoridation is the most efficient public health measure because only seventeen per cent of the children taking tablets received them daily throughout life.

Handicapped children: behavioural and co-ordination characteristics affecting the delivery of dental care.

Statistical analysis of data from a field survey of 132 handicapped children confirmed that a questionnaire approach is reliable in identifying children with potential behavioural and co-ordination problems within a dental environment. Assessment of the behaviour and co-ordination of 2,082 handicapped children aged 3-16 years, inclusive, suggested that approximately 53 per cent were manageable in a normal dental surgery and 79 per cent had the necessary co-ordination for routine dental care.

The dental care of handicapped children in South Australia.

Sixty-two per cent of handicapped children had a dentist willing to provide treatment; 55 per cent and 41 per cent were examined and were treated at least annually. Approximately 58 per cent were reported by their guardians to be manageable in general dental practice. Treatment was provided under general anaesthesia for 29 per cent of the children, although 39 per cent were considered by their guardians to require this procedure. Factors related to type and frequency of dental treatment are discussed.