Researchers have sounded a warning about the risk posed by multidrug-resistant tuberculosis (MDR-TB) in West Africa, which they say is a much bigger problem than previously thought.
The World Health Organisation (WHO) estimates the prevalence of multidrug resistance in new and retreatment cases to be 2% and 17% respectively, but a new study found the real incidence was 6% in new cases and 35% in retreated ones.
“Multidrug-resistant and pre-extensively drug-resistant tuberculosis strains are already widely circulating,” said Martin Antonio, who led the study published in the journal BMC Medicine.
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 – defined as resistant to two or more of the first-line drugs.
Extensively drug-resistant TB (XDR-TB), which is resistant to the second-line drugs that are used if first-line treatment fails, was found at all study sites. Ghana, with 35%, was the highest.
MDR-TB prevalence was highest among patients previously treated for TB in Bamako, Mali (59%) and in Ibadan (39%) and Lagos (66%), Nigeria.
“In Lagos, 32% of new TB patients tested positive for the MDR-TB strains,” Florian Gehre, a postdoctoral researcher and co-author of the paper said.
“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.”
The incidence of XDR-TB and multidrug-resistant MDR-TB is rising globally. Cosmos has reported India is probably the biggest concern, but the disease is increasingly causing problems in the West, with travellers catching the disease and bringing it home in increasing numbers.
But Antonio warns that the fragile health systems of the West African region were easily be overwhelmed by infectious disease epidemics “as seen in the recent Ebola outbreak”.
“We recommend that efforts be put in place for containment of a potential West African TB epidemic at the earliest possible stage,” he said.
Bill Condie is a science journalist based in Adelaide, Australia.
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