Tuberculosis Prevention Strategies Research Articles

Assessment of tuberculin reactivity of BCG-vaccinated infants in Zaria, Nigeria

Introduction: Tuberculosis (TB) is a serious public health problem associated with high morbidity and mortality. BCG vaccination as part of TB prevention strategy is faced with many challenges. The study sought to determine post BCG vaccination scarring and tuberculin reactivity, which may serve as useful indicators of routine BCG vaccination in infants. Materials and Methods: The study was descriptive cross-sectional. Infants were selected and physically examined for presence and size of BCG scar. Mantoux test was performed. Data were analyzed using statistical package for the social sciences software (SPSS version 16.0). Chi-square and Fisher's exact tests were used for association between categorical variables while Pearson's correlation co-efficient was used for the correlation between BCG scar size and Mantoux reaction. P ≤ 0.05 was considered significant. Results: The male:female ratio of the subjects was 1.6:1.0 with a mean birth weight of 3.2 ± 0.4kg.Mean age at Mantoux test was 19.0 ± 3.0 weeks and the prevalence of BCG scar was 81.5% with a mean scar size of 5.3 ± 3.2mm. Mantoux test was positive in 202 (56.7%), negative in 133 (37.4%), and indeterminate in 21 (5.9%) infants. The Mantoux reaction was significantly associated with the age interval between BCG administration and time of Mantoux test (χ2 = 54.17, P < 0.05), the infants' gender (χ2 = 31.23, P < 0.05) and their nutritional status (χ2 = 22.60, P < 0.05). The reaction was not significantly associated with the social class of the infants' parents. Conclusion: The study demonstrated high prevalence of BCG scar and high Tuberculin skin test reaction. Regular evaluation of BCG vaccination is recommended using TST and scar observation as adjuncts to strengthen BCG vaccination processes for effective tuberculosis prevention.

Risk of active tuberculosis in immigrants: effects of age, region of origin and time since arrival in a low‐exposure setting

To estimate the risk of active tuberculosis (TB) in immigrants to VICtoria, Australia, as a function of time since arrival and stratified by age group and region of origin. DESIGN, SETTING AND SUBJECT: Longitudinal study of the incidence of active TB in VICtorian immigrants, excluding New Zealanders, who arrived in Australia between 1975 and 2007. VICtorian immigration data were used to describe annual arrival cohorts by age and region of origin, and TB case notification data for 1995 to 2010 were matched to the cohorts. Survival analysis was performed to determine incidence rates of active TB. Incidence of active TB, stratified by age, region of origin and time since arrival in Australia. Incidence of active TB following immigration to Australia was highly dependent on region of origin, with the highest risks being in immigrants from South Asia and sub-Saharan Africa. For immigrants from high-risk regions (Asia, Africa and the Pacific), the incidence of active TB infection was 100-150 per 100 000 person-years in the first 6 years following immigration. Overall, we estimate that 50% of TB occurred within 7 years of arrival. A bimodal age distribution was evident, with peaks of incidence in 20-24-year-olds and 70-74-year-olds. Our data show that substantial risk of TB in VICtorian immigrants persists well beyond the first 2-3 years following arrival, and that risk is highly dependent on region of origin. The regional dependence suggests that public health strategies would benefit from more refined regional stratification of risk, which could be used to determine risk thresholds for the use of TB prevention strategies and predict rates of TB in Australia following particular patterns of immigration.

Thibela TB: Design and methods of a cluster randomised trial of the effect of community-wide isoniazid preventive therapy on tuberculosis amongst gold miners in South Africa

Background South Africa has the third highest annual number of new tuberculosis (TB) cases globally. The resurgence of TB which has particularly affected gold miners in South Africa, is attributed to occupational risk factors for TB including silica dust exposure and high HIV prevalence. Isoniazid preventive therapy (IPT) is recommended for individuals at high risk to prevent both HIV-related TB and silicotuberculosis, but global uptake has been poor. We describe the design of a cluster randomised study, “Thibela TB”, which compares routine IPT targeted to those identified as at higher risk of TB (due to HIV infection or silicosis) against a “community-wide” approach in which IPT is offered to all employees. The trial is registered with the Current Controlled Trials: Registration number ISRCTN63327174. Methods We describe the rationale for the intervention of community-wide IPT, drawing on studies conducted in 1950–1960s in the pre-HIV era. The design of the study, including the definition of the cluster, is presented and advantages and limitations of such a design are discussed. Conclusion If successful in reducing TB incidence and prevalence, this trial has potential to make a major contribution to TB control policy in high HIV settings, providing evidence concerning efficacy, and additionally safety and population-level effects on drug susceptibility patterns. Such rigorous evaluation is essential to provide policy makers with an evidence base to guide community-level TB prevention strategies.

Disseminated bacille Calmette-Guerin disease in HIV-infected South African infants

To determine the population-based incidence of disseminated bacille Calmette-Guérin (BCG) disease in HIV-infected infants (aged <or= 1 year) in a setting with a high burden of tuberculosis and HIV infection coupled with a well-functioning programme for the prevention of HIV infection in infants. The numerator, or number of new cases of disseminated BCG disease, was derived from multicentre surveillance data collected prospectively on infants with a confirmed HIV infection during 2004-2006. The denominator, or total number of HIV-infected infants who were BCG-vaccinated, was derived from population-based estimates of the number of live infants and from reported maternal HIV infection prevalence, vertical HIV transmission rates and BCG vaccination rates. The estimated incidences of disseminated BCG disease per 100 000 BCG-vaccinated, HIV-infected infants were as follows: 778 (95% confidence interval, CI: 361-1319) in 2004 (vertical HIV transmission rate: 10.4%); 1300 (95% CI: 587-2290) in 2005 (transmission rate: 6.1%); and 1013 (95% CI: 377-1895) in 2006 (transmission rate: 5.4%). The pooled incidence over the study period was 992 (95% CI: 567-1495) per 100 000. Multicentre surveillance data showed that the risk of disseminated BCG disease in HIV-infected infants is considerably higher than previously estimated, although likely to be under-estimated. There is an urgent need for data on the risk-benefit ratio of BCG vaccination in HIV-infected infants to inform decision-making in settings where HIV infection and tuberculosis burdens are high. Safe and effective tuberculosis prevention strategies are needed for HIV-infected infants.

AIDS-related tuberculosis in Rio de Janeiro, Brazil.

BackgroundWe studied the incidence of tuberculosis, AIDS, AIDS deaths and AIDS-TB co-infection at the population level in Rio de Janeiro, Brazil where universal and free access to combination antiretroviral therapy has been available since 1997.Methodology/Principal FindingsThis was a retrospective surveillance database match of Rio de Janeiro databases from 1995–2004. Proportions of tuberculosis occurring within 30 days and between 30 days and 1 year after AIDS diagnosis were determined. Generalized additive models fitted with cubic splines with appropriate estimating methods were used to describe rates and proportions over time. Overall, 90,806 tuberculosis cases and 16,891 AIDS cases were reported; 3,125 tuberculosis cases within 1 year of AIDS diagnosis were detected. Tuberculosis notification rates decreased after 1997 from a fitted rate (fR per 100,000) of 166.5 to 138.8 in 2004. AIDS incidence rates increased 26% between 1995 and 1998 (30.7 to 38.7) followed by a 33.3% decrease to 25.8 in 2004. AIDS mortality rates decreased dramatically after antiretroviral therapy was introduced between 1995 (27.5) and 1999 (13.4). The fitted proportion (fP) of patients with tuberculosis diagnosed within one year of AIDS decreased from 1995 (24.4%) to1998 (15.2%), remaining stable since. Seventy-five percent of tuberculosis diagnoses after an AIDS diagnosis occurred within 30 days of AIDS diagnosis.Conclusions/SignificanceOur results suggest that while combination ART should be considered an essential component of the response to the HIV and HIV/tuberculosis epidemics, it may not be sufficient alone to prevent progression from latent TB to active disease among HIV-infected populations. When tuberculosis is diagnosed prior to or at the same time as AIDS and ART has not yet been initiated, then ART is ineffective as a tuberculosis prevention strategy for these patients. Earlier HIV/AIDS diagnosis and ART initiation may reduce TB incidence in HIV/AIDS patients. More specific interventions will be required if HIV-related tuberculosis incidence is to continue to decline.

Cervical Tuberculosis: A Decision Tree for Protecting Healthcare Workers

The clinical presentation of cervical tuberculosis (TB) is a unique challenge to the otolaryngologist. To minimize the risk of nosocomial transmission, otolaryngologists must suspect the diagnosis and be familiar with recommendations for TB prevention. Scientific review. We review current literature and recent changes in TB prevention strategies including the Centers for Disease Control and Prevention "Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005." Nosocomial transmission may occur from either unrecognized pulmonary disease or from aerosolization of tubercle bacilli during diagnostic procedures. History of prior TB infection, residence in a country where TB is endemic, close contact with a TB patient, or positive tuberculin skin test should raise suspicion of cervical TB. Physical examination findings may include painless, unilateral cervical lymphadenopathy. Children and human immunodeficiency virus infected patients present unique challenges, as these groups may have atypical presentations. When cervical TB is suspected, the provider should always screen for pulmonary and laryngeal disease. Fine needle aspiration with polymerase chain reaction or culture may accurately identify cervical TB. In rare cases, excisional biopsy may be required. To facilitate interpretation and rapid diagnosis while minimizing risk to health care providers, we provide a decision tree based on new federal guidelines and the clinical experience of a team of infectious disease specialists and otolaryngologists.

Preventing TB in travellers

Travellers can be at risk of becoming infected with Mycobacterium tuberculosis. In this article we look at the choice of tuberculosis prevention strategies available

Boosting of tuberculin sensitivity among Southeast Asian refugees.

Following an initial negative Mantoux tuberculin skin test, a second test, given as soon as 1 wk later, has been shown to elicit markedly larger reactions (boosting) in 20 to 40% of refugees tested in the United States. We conducted a study to determine the explanation for this phenomenon. Using the Mantoux method of intradermal skin testing, 2,469 refugees from Southeast Asia were initially tested with tuberculin followed by sequential retesting 7 and/or 90 d later. They were also tested initially with nontuberculous mycobacterial antigens. A high proportion (35.5%) of Southeast Asian refugees had reactions (> or = 10 mm induration) to an initial tuberculin test, and 30.9% of the nonreactors exhibited boosting on a subsequent tuberculin test. Boosting, unlike reactivity to the initial tuberculin test, was not associated with exposure to a person with tuberculosis. However, boosting was associated with reactivity to nontuberculous mycobacterial antigens and a history of bacille Calmette-Guérin (BCG) vaccination. Boosting in this population is therefore attributable to environmental exposure to nontuberculous mycobacteria that are endemic in Southeast Asia or to BCG vaccination, rather than to remote infection with Mycobacterium tuberculosis. Sequential tuberculin screening and preventive therapy of persons with boosted reactions is not recommended as a tuberculosis prevention strategy in this population.