Tuberculosis transmission in the Indigenous peoples of the Canadian prairies.

Smit Patel,Courtney Heffernan,Dick Menzies,Ambikaipakan Senthilselvan,Vernon Hoeppner,Carmen Lopez-Hille,Richard Long,Sara Christianson,Pamela Orr,Malcolm King,Meenu Sharma,Duncan Saunders,Dennis Kunimoto,Jody Boffa,Joyce Wolfe,Catherine Paulsen,Kathleen Mcmullin,Joan A Caylà

doi:10.1371/journal.pone.0188189

Abstract

SettingThe prairie provinces of Canada.ObjectiveTo characterize tuberculosis (TB) transmission among the Indigenous and non-Indigenous Canadian-born peoples of the prairie provinces of Canada.DesignA prospective epidemiologic study of consecutively diagnosed adult (age ≥ 14 years) Canadian-born culture-positive pulmonary TB cases on the prairies, hereafter termed “potential transmitters,” and the transmission events generated by them. “Transmission events” included new positive tuberculin skin tests (TSTs), TST conversions, and secondary cases among contacts.ResultsIn the years 2007 and 2008, 222 potential transmitters were diagnosed on the prairies. Of these, the vast majority (198; 89.2%) were Indigenous peoples who resided in either an Indigenous community (135; 68.2%) or a major metropolitan area (44; 22.2%). Over the 4.5-year period between July 1st, 2006 and December 31st 2010, 1085 transmission events occurred in connection with these potential transmitters. Most of these transmission events were attributable to potential transmitters who identified as Indigenous (94.5%). With a few notable exceptions most transmitters and their infected contacts resided in the same community type. In multivariate models positive smear status and a higher number of close contacts were associated with increased transmission; adjusted odds ratios (ORs) and 95% confidence intervals (CIs), 4.30 [1.88, 9.84] and 2.88 [1.31, 6.34], respectively. Among infected contacts, being Indigenous was associated with disease progression; OR and 95% CI, 3.59 [1.27, 10.14] and 6.89 [2.04, 23.25] depending upon Indigenous group, while being an infected casual contact was less likely than being a close contact to be associated with disease progression, 0.66 [0.44, 1.00].ConclusionIn the prairie provinces of Canada and among Canadian-born persons, Indigenous peoples account for the vast majority of cases with the potential to transmit as well as the vast majority of infected contacts. Active case finding and preventative therapy measures need to focus on high-incidence Indigenous communities.

Highlights

Tuberculosis (TB) is an ongoing global public health problem
Most of these transmission events were attributable to potential transmitters who identified as Indigenous (94.5%)
In the prairie provinces of Canada and among Canadian-born persons, Indigenous peoples account for the vast majority of cases with the potential to transmit as well as the vast majority of infected contacts

Summary

Introduction

Tuberculosis (TB) is an ongoing global public health problem. Within high-income, low-incidence, countries it most commonly affects minority groups and the impoverished. In Canada, for as long as national reports have been filed, Indigenous peoples have had higher rates of TB than any other population group [1]. In 1982, the Constitution Act of Canada recognized three major groups of Indigenous peoples: First Nations, who may be registered or un-registered with the federal government under the terms of the Indian Act, Metis, self-identified persons of mixed Indigenous and non-Indigenous ancestry, and Inuit [4]. According to the Public Health Agency of Canada (PHAC), TB cases among the First Nations and Metis population in the prairie provinces of Alberta, Saskatchewan and Manitoba contribute more than one-half of the total Indigenous TB cases in all of Canada [2]

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Conclusion