Abstract
The aims of the present study were to identify risk factors associated with latent tuberculosis (TB), examine the development of active disease among contacts, and assess the effectiveness of treating latent infection in indigenous Brazilians from January 2006 to December 2011. This was a retrospective study consisting of 1,371 tuberculosis contacts, 392 of whom underwent treatment for latent infection. Morbidity-from-TB data were obtained from the Information System for Disease Notification (SINAN) database, and the contacts’ data were collected from the clinical records using forms employed by Special Department of Indigenous Health (SESAI) multidisciplinary teams, according to SESAI’s instructions. The variables that were associated with latent infection among the contacts were age (odds ratio [OR]: 1.03; 95% confidence interval [CI]: 1.02–1.04) and close contact with a smear-positive index case (OR: 2.26, 95% CI: 1.59–3.22). The variables associated with the development of active TB among the contacts were a tuberculin skin test (TST) ≥10 mm (relative risk [RR]: 1.12, 95% CI: 1.07–1.17), age (RR: 1.01, 95% CI: 1.00–1.03), and treatment of latent infection (RR: 0.03, 95% CI: 0.01–0.27). The estimated number of latent infection treatments needed to prevent one case of active TB among the contacts was 51 treatments (95% CI: 33–182). In contacts with TST ≥10 mm, 10 (95% CI: 6–19) latent infection treatments were necessary to prevent one case of active TB. Age and close contact with a smear-positive index case were associated with latent TB. Screening with TST is a high priority among individuals contacting smear-positive index cases. Age and TST are associated with the development of active TB among contacts, and treatment of latent infection is an effective measure to control TB in indigenous communities.
Highlights
Over the past 500 years, Brazil’s indigenous population has been affected by a tuberculosis (TB) epidemic characterized by frequent treatment failure and high mortality rates [1,2,3,4,5,6,7,8]
For contacts over 50 years of age, 11 people had to be treated to prevent one active case; contacts aged 20–49 years required 30 treatments, and contacts aged 0–4 years required 56 treatments. These findings indicate that the treatment of latent infection is more effective in contacts who are older than 50 years
The variables associated with latent infection were age (OR: 1.03, 95% confidence interval (CI): 1.02–1.04) and contact with a smearpositive index case (OR: 2.26, 95% CI: 1.59–3.22)
Summary
Over the past 500 years, Brazil’s indigenous population has been affected by a tuberculosis (TB) epidemic characterized by frequent treatment failure and high mortality rates [1,2,3,4,5,6,7,8]. Despite the implementation of directly observed therapy (DOTS) and a significant decrease in incidence from 700 to 260 cases per 100,000 inhabitants in the indigenous populations of Dourados [9], new interventions are needed to control the disease. The source of TB infection is often an individual with the pulmonary form of the disease. One single source is estimated to infect an average of 10 to 15 contacts within the community per year [16]. Greater frequency and longer duration of contact with bacilliferous cases are associated with higher proportions of infected individuals [17]. Self-supervised daily isoniazid regimens have completion rates of 60% or less in typical settings, attributable largely to the regimen’s duration of $6 months [20,25]
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