 By
the time he was threatened with jail time, Victor-Miguel
Sebastian-Rosales, a 26-year-old refugee from Peru, had
already ignored two court orders to take his medication
for tuberculosis (TB). In December 2000, Quebec Superior
Court Justice Jean Crepeau warned him to comply or be
jailed for up to eight months, thereby no longer posing
a public health risk.
MUCH
OF A MUCHNESS
Cases like these are a dramatic reminder that TB is
still very much with us. Canadian TB rates have been
stable for several years, at about 1,700 new cases here
each year. But for the past six years a dangerously
high number of them have been drug-resistant or multi-drug
resistant (MDR). "You can get drug-resistant TB in two
ways," explains Dr Rob Stirling, a specialist in TB
prevention and control at Health Canada's Centre for
Infectious Disease Prevention and Control. "You can
become infected with a strain of resistant TB. Alternatively,
you might have drug-susceptible TB, but the TB becomes
resistant during treatment because of inadequate or
inappropriate treatment or because the person doesn't
take all of their prescribed medication."
CRUCIAL
DIGILENCE
Because Mycobacterium tuberculosis grows very
slowly, antibiotics must be taken long after the person
feels well, and treatment for MDR TB is longer as well
as more expensive. This is where patients go astray
� they think they're better, so they stop taking their
pills. "The 'classic' anti-TB therapy is six months
long and the drug costs are small: four drugs � isoniazid
(INH), rifampin (RMP), pyrazinamide and streptomycin
or ethambutol � for two months, followed by INH and
RMP for four months, " says Dr Wendy Wobeser, of the
Division of Infectious Diseases at Queen's University.
"But with MDR TB, at least four and sometimes five drugs
are taken for a minimum of 18 months, with up to 100-fold
higher costs and greater toxicities."
WATCH
THE MEDICINE GO DOWN
According to the World Health Organization, the most
effective strategy for preventing drug resistance is
directly observed therapy (DOT), where a nurse or public
health worker watches the patient swallow the medication.
"In the first two months of the six-month treatment
you're supposed to take pills every day; but in the
remaining four months the medications can be taken either
daily or twice a week.The Canadian Tuberculosis Standards
(CTS) recommend DOT for the latter case," says Dr Stirling.
The CTS also recommends DOT for all prisoners in the
federal correction system, since in 1998, one out of
every five offenders entering federal prisons was infected
with TB. Despite these high levels of infection, conversion
rates are very low, suggesting that existing programs
are successful in curbing the spread of TB.
DOT is also used on First Nations
reserves where the TB rate is almost four times higher
than among other Canadians, due to a large reservoir
of infection and poor socio-economic conditions. "Specialists
and GPs can play a role by recognizing and diagnosing
active TB, so that patients can be treated and TB spread
can be interrupted," says Dr Wobeser.
In 2003, the Canadian Tuberculosis
Laboratory Surveillance System reported that of 1,379
isolates from TB patients, 12.5% were resistant to one
or more first-line anti-TB drugs and 1.5% were MDR TB
strains. These rates have remained steady since the
surveillance system was started in 1998. The law requires
that all TB cases be reported, and since isolates are
tested in most cases, this is a fairly good estimate
of resistant TB levels. BC, Ontario, and Quebec � provinces
with the largest numbers of immigrants from countries
with an elevated rate of resistant TB � have consistently
reported the highest numbers of MDR TB isolates over
this time period. The highest global prevalence of MDR
TB coincides with the world's fastest growing HIV infection
areas, Eastern Europe and Central Asia. TB and AIDS
organizations worldwide are banding together to prevent
this dual plague.
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