The
prevalence of multidrug-resistant tuberculosis (MDR-TB) is unexpectedly high in
eight West African countries, research by the West African Network of
Excellence for TB, AIDS and Malaria (WANETAM) has revealed.
According
to the research published in the open access journal, BMC Medicine, MDR-TB
could become a serious public health threat in West Africa unless effective
surveillance and control measures are implemented.
In
a press release from Medical Research Council Gambia office (MRCG), Professor
Martin Antonio, principal investigator at MRCG, who led WANETAM’s TB-related
activities, said: “To our surprise, we found that multidrug-resistant and
pre-extensively drug-resistant tuberculosis strains are already widely
circulating, and that drug resistance is a much bigger problem in West Africa
than previously anticipated.
“WHO
estimates the prevalence of multidrug resistance in new and retreatment cases
to be 2% and 17% respectively, but we found that it is 6% and 35% respectively.
“We
recommend that efforts be put in place for containment of a potential West
African TB epidemic at the earliest possible stage. This is especially important, as West Africa
with its 245 million inhabitants, is one of the poorest regions globally, whose
fragile health systems can easily be overwhelmed by infectious disease
epidemics, as seen in the recent Ebola outbreak.
“Analysis
of 974 bacterial samples collected from patients with TB revealed that 39% were
resistant to at least one first-line drug and 22% were
multidrug-resistant. Pre-extensively
drug-resistant TB isolates were found to be present at all study sites, with
Ghana showing the highest proportion, where 35% of MDR samples were
pre-extensively drug-resistant.
“Multidrug-resistant
bacteria are resistant to two or more of the first-line drugs used for the
treatment of a disease. Pre-extensively
drug-resistant bacteria are on the verge of developing into extensively
drug-resistant bacteria, which are resistant to the second-line drugs that are
used if first-line treatment fails.
“MDR-TB
prevalence was highest among patients previously treated for TB in Bamako, Mali
(59%) and in Ibadan (39%) and Lagos (66%), Nigeria. Bacteria isolated from these retreatment
patients were four times more likely to be resistant to one or more first-line
drugs when compared to bacteria isolated from new patients.
“Due
to poor laboratory infrastructure and inadequate capacity, at the start of
WANETAM, data on drug-resistant TB prevalence in West Africa were scarce so
prevalence was assumed to be comparably low and not considered a major public
health problem. Our data shows that this may not be the case.
“In
order to take steps to remedy the lack of laboratory infrastructure and to
generate comprehensive data on drug resistance prevalence in West Africa,
WANETAM trained local laboratory staff to perform routine diagnostics such as
standardised smear microscopy and mycobacterial culture.”
Dr
Florian Gehre, a postdoctoral researcher and first author of the paper said:
“In Lagos, 32% of new TB patients tested positive for the MDR-TB strains. Even
when considering a potential sampling bias in the study, it is uncommon for new
patients to acquire MDR-TB, except if patients with MDR-TB strains transmit
these strains directly to new patients or new patients infect each other.”
Professor
Souleymane Mboup, head of the Bacteriology Virology Department at the
University Hospital Le Dantec, University of Dakar, Senegal, and the overall
principal investigator for the WANETAM project said: “This is the first time
that leading scientists and research institutes in West Africa joined forces to
create a research network that provides research opportunities, fosters
collaborations, builds capacity and trains members in basic and advanced
laboratory techniques to independently conduct TB drug resistance surveys.
“The
infrastructure built by WANETAM will help countries in West Africa to respond
effectively to emerging public health threats and to conduct trials to address
local health needs and inform health policies.”
Professor
Umberto D’Alessandro, MRC Gambia Unit director, said: “Besides building
infrastructures and training local research teams, WANETAM has been able to
produce highly relevant and high quality information for the control of TB in
West Africa.
“I
hope WANETAM will continue to provide a major contribution to the fight against
diseases of public health importance in Africa.”
WANETAM,
founded in 2008, comprises nine study sites in Burkina Faso, The Gambia, Ghana,
Guinea-Bissau, Mali, Nigeria, Senegal and Togo.
The
WANETAM study was the first to achieve a comprehensive overview of drug
resistance in the sub-region.
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