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More than half of all healthcare workers in the developing world, including Africa, are unknowingly infected with latent tuberculosis, according to a report available on the open-access Science and Development Network website
The study, published in the online journal Medicine by the open-source Public Library of Science, highlights the risk of tuberculosis transmission from patients to healthcare workers - and onward into the general community.
According to the authors, who include Rajnish Joshi of the Mahatma Gandhi
Institute of Medical Sciences in Maharashtra state in India and Arthur
Reingold of the University of California Berkeley in the USA, the
tuberculosis infections also have a subsequent negative impact on health
services, although this problem is frequently neglected in countries that
lack the resources or political will to prevent it.
The researchers, who include Dick Menzies and Madhukar Pai of the Montréal Chest Institute at McGill University in Canada, reviewed 51 published studies concerning healthcare workers and tuberculosis in several developing countries, including India, Malawi, Uganda, South Africa and Peru.
Their analysis shows that, on average, 54% of the healthcare workers have
latent tuberculosis, in which the microscopic bacterium responsible for the
disease causes no symptoms but remains in the body. About a third of the
world's population is latently infected with Mycobacterium tuberculosis.
The scientists found that the level of active disease among healthcare
workers is higher than the general population. The longer that healthcare
workers were exposed to tuberculosis, the higher the prevalence of latent
infection. Many cases could be directly attributed to occupational exposure.
Certain workplaces, such as in-patient tuberculosis facilities, laboratories
and emergency facilities, carried a higher risk of infection. Some
occupations, such as radiology technicians and nurses, were also more likely
to be infected.
More than 90 per cent of the world's tuberculosis cases are found in
hospitals in developing countries, from Russia to Brazil. Many of these
facilities lack the resources to prevent tuberculosis transmission.
But simple measures, such as early diagnosis, segregation of infectious
patients and better training of healthcare workers, can make a big
improvement, authors note.
They also say that further research into cheap and effective prevention
measures in resource-limited settings is needed — particularly with the
emergence of extensively drug-resistant tuberculosis in countries such as
South Africa.
Multi-drug resistant tuberculosis is more widespread than thought, warn
researchers from the Global Project on Anti-tuberculosis Drug Resistance
Surveillance.
Misusing antimicrobial drugs can lead to multi-drug resistant tuberculosis
which is defined as resistant to the two most powerful anti-tuberculosis
drugs, Isoniazid and Rifampicin.
But researchers warn that multi-drug resistant tuberculosis is only the
precursor to extensively drug resistant tuberculosis, which is potentially
incurable with available drugs. It resists all standard tuberculosis drugs
and at least one of three second-class drugs.
Looking at four of the six most widely used tuberculosis drugs, the
scientists found that both multiple and extensive drug resistance were
causing growing numbers of new infections, especially in parts of China and
the former Soviet Union. The results have been published in the medical
journal The Lancet.
In the 79 countries surveyed between 1999 and 2002, multi-drug resistance in new tuberculosis cases ranged from zero to 14 per cent. Resistance to just one drug ranged from zero to 57 per cent. In Botswana, however, there has been a worrying increase in resistance to any available tuberculosis drugs.
The researchers estimate that 424,000 cases of multi-drug resistant
tuberculosis emerged worldwide in 2004. Half of the new cases of multi-drug
resistant tuberculsosis werein China, India and Russia alone.
Expensive drugs are needed to treat multi-drug resistant tuberculosis.
Because the multi-drug treatment is lengthy and difficult, patients often
fail to follow it through. This can lead to extensively resistant
tuberculosis, which is resilient to first- and second-line drugs.
The emergence of extensively resistant strains is 'extremely worrisome',
says the report. This type of tuberculosis is particularly worrying for
people with HIV/AIDS or otherwise compromised immune systems.
Tuberculosis
killed almost two million people in 2004, many of whom were co-infected with
HIV (Human Immunodeficiency Virus, which causes AIDS).
"The findings of the Global Project emphasise the importance of
implementing
sound tuberculosis control activities to prevent further creation of
multi-drug resistance," said Mario Raviglione of the World Health
Organisation (WHO), which led the project with the International Union
Against Tuberculosis and Lung Disease.
The results also reveal the need to include high-quality treatment for
multi-drug resistance in routine control programmes, said Raviglione, head
of the WHO's Stop TB Department. He warned that extensively drug resistant
tuberculosis will be fatal, particularly in regions (such as South Africa)
with considerable numbers of HIV infections.
The second Open Forum on TB Drug Development last month stressed that
ensuring the effective use of drugs is as crucial to tuberculosis control as
developing new drugs.
"What we need first and foremost is innovation," said Maria Freire,
president of the Tuberculosis Alliance that convened the forum in London,
England. - www.SciDev.Net
More information:
Article
courtesy and © Scidev.net
International Union Against Tuberculosis and Lung Disease
http://www.iuatld.org
World Health Organisation www.who.int
Global Project on Drug Resistance Surveillance
http://www.who.int/tb/dots/dotsplus/surveillance/en/index.html
Public Library of Science www.plos.org
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