Tuberculosis in First Nations communities

• History
• Tuberculosis infection
• Tuberculosis disease
• Housing and tuberculosis
• Linking the data to the Tuberculosis Elimination Strategy
• Tuberculosis in First Nations communities, 1999 report

History

During the early decades of the 20th century, a terrible epidemic of tuberculosis (TB) occurred in the Canadian First Nations population. It is probable that First Nations people had less immunity to European strains of TB, and drugs to cure TB were not yet available. Malnutrition increased the risk of disease, and confinement on crowded reservations allowed the disease to spread rapidly. Death rates were in excess of 700 per 100,000, among the highest ever reported in a human population. Death rates from TB meningitis in children aged 0-4 years ranged from 500 to 2000 per 100,000, and overall TB death rates among children in residential schools were as high as 8000 per 100,000, during the 1930s and 1940s.

Tuberculosis infection

Elders in many First Nations communities lived through periods when TB rates - and the risk of being infected - were extremely high. It is generally assumed that once people are infected with Mycobacterium tuberculosis bacteria, they remain infected for life. Table 1 shows the results of community surveys to detect TB infection, among First Nations people aged 30 years and more.

Table 1. The estimated prevalence of TB infection among First Nations people aged 30+ years, in the on-reserve populations of British Columbia and Saskatchewan (1995-1998). Note: 95% confidence intervals in brackets.

Tuberculosis disease

National rates of TB disease from 1990 to 2000 are provided in Table 2. First Nations TB rates remain 8-10 times higher than overall Canadian rates, and 20-30 times higher than Canadian-born, non-Aboriginal rates. Despite this, 2000 national TB case tally of 86 is the lowest ever reported in the First Nations, on-reserve population. The notification rate in 1999 was very high due to the occurrence of several large outbreaks. Of the areas where Health Canada's First Nations and Inuit Health Branch (FNIHB) provides TB programs, TB rates are highest in the four western provinces (B.C., Alberta, Saskatchewan, and Manitoba), and northwestern Ontario (the communities of Sioux Lookout Zone).

Table 2. National, age-standardized notification rates of TB disease in the First Nations, on-reserve and overall Canadian populations, and standardized morbidity ratios (SMR) (1990-2000). The data includes reported TB cases in the First Nations, on-reserve populations of British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, New Brunswick, and Nova Scotia.

The SMR figure represents the First Nations rate divided by the overall Canadian rate, expressed as a percentage.

Figure 1 shows the rates of TB in four different age categories, in the on-reserve populations of the four western provinces. Rates of pediatric TB (age 0-14 years) decreased from 187.1 per 100,000 to 25 per 100,000 from 1990 to 2000. The majority of pediatric cases (79.2 %) during this time period were reported in Saskatchewan. The decrease from 1990 to 2000 is encouraging, although the 1999 rate of 72 per 100,000 was 29 times higher than the overall Canadian rate that year. In 2000, people aged 55 years and older had the highest rate of the four age groups, at 123 per 100,000.

Risk factors

HIV, diabetes, substance abuse, and other factors that weaken the immune system can increase the risk of TB disease after infection. These factors may be present in many TB endemic communities, increasing the risk of disease and spread:

• The proportion of HIV and AIDS cases attributed to Aboriginal persons in Canada increased throughout the 1990s.
• Diabetes prevalence is 3-5 times higher in the First Nations population.
• In 2000, substance abuse was a reported risk factor in 47.6% of TB cases living on reserve in B.C. and Alberta.

Case fatality

TB caused or contributed to a death in 4.1% of First Nations TB cases in Canada between 1990 and 2000. The risk of death is highly age-dependent, and increases with age (Figure 2). Only one of 803 childhood TB cases (aged 0-14 years) died from TB, while 19.8% of cases among people aged 75 years or over were fatal.

Infectious TB

If a person has pulmonary or laryngeal TB disease, and TB bacteria have been found in a sputum sample using microscopy or culture, that person is considered infectious and can spread tuberculosis to others. Figure 3 shows the proportion of total TB cases which were infectious, by age group, in the First Nations population between 1990 and 2000. The distribution of total infectious TB cases by age group is then shown in Figure 4. These data indicate that a high proportion of infectious cases occur among young adults, aged 15-34 years.

Housing and Tuberculosis

Overcrowded living conditions increase the contact rate between individuals, and the risk of person-to-person transmission from infectious TB cases to others. The overall Canadian population has a housing density of 0.4 persons per room (0.4 ppr). The corresponding statistic for First Nations people living on reserve is 0.7 ppr. First Nations communities with higher average housing densities have higher TB rates (Figure 5). The ten communities with the highest number of reported TB cases between 1997 and 2000 all had housing densities of 0.8 or more, and eight of them had 1.0 ppr or more. Eight of these communities were also located in remote areas, with no road access.

Linking the data to the Tuberculosis Elimination Strategy

These data show that the burden of TB is much higher among First Nations people than among non-First Nations people in Canada. Programs to control and prevent TB in this population must therefore be maintained and strengthened. Several elements of the National Tuberculosis Elimination Strategy are being implemented effectively. Compliance rates for treatment of disease are very high, and pediatric rates are decreasing from year to year. Directly observed treatment of TB patients and rapid investigation of high-risk contacts are difficult and challenging tasks, especially in remote communities where TB outbreaks often occur.

Large outbreaks, high pediatric TB rates, and the high risk of infectious TB in young adults all confirm that a cycle of transmission still exists in many First Nations communities. Many people in this population are infected with TB bacteria, and problems such as substance abuse, diabetes, and HIV can increase the risk of disease following infection. Young adults at high risk for infectious TB are often highly mobile, moving from community to community, on and off reserve. Overcrowded housing then increases the likelihood that infectious cases will spread TB to others. This cycle of transmission must be stopped, so that younger generations can grow up free of infection and TB is eliminated.