27/07/12

New method to detect drug-resistant leishmaniasis

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[KATHMANDU] Researchers have developed a faster and more reliable method to detect drug-resistant visceral leishmaniasis, the most serious form of the parasitical infection

Leishmaniasis, a neglected disease, is transmitted by Leishmania donovani, a parasite spread by sandflies. The parasite can infect the skin, mucous lining or the abdomen, of which the third, also known as visceral leishmaniasis (VL), can turn fatal if untreated.

Between 162,100 and 313,600 cases of VL are reported annually in South Asia, mostly in the northern Indian state of Bihar, eastern and central Nepal, and Bangladesh, which accounts for 80 per cent of the global burden.

The infection is endemic in 60 countries, with the heaviest burdens in Bangladesh, Brazil, India, Nepal, and Sudan.

A recent EU-funded study involving researchers from institutes in Belgium, Germany, India, Nepal, Switzerland, and the UK analysed resistance in leishmania strains isolated from 50 patients in India and Nepal.

Drugs containing antimony or ‘antimonials’, mainly sodium stiboglucante, have long been the primary form of treatment for VL, but in recent years some strains have become resistant, said the study whose findings were published in the Journal of Infectious Diseases last month (29 June).

The standard method for identifying resistance involves culturing and testing infected cells in a laboratory, but this takes at least five days to process and sometimes produces erroneous results.

The new method builds on recently completed genetic sequencing of the leishmania genome. It uses a technique called ‘polymerase chain reaction’ or PCR that multiplies and amplifies gene sequences to detect genetic mutations that cause resistance to antimonials.

It is "not only an easier and faster test, but is also a more reliable one," explained lead author of the study, Manu Vanaerschot, at the Institute of Tropical Medicine, Antwerp (ITG), in Belgium. 

"This work contributes to a more efficient elimination strategy for VL, as is currently taking place in India, Nepal and Bangladesh through the Kala-Azar Elimination Programme," said Vanaerschot, referring to a campaign launched in 2005 by the three countries to eliminate VL by 2015. 

The new method is an epidemiological rather than a diagnostic tool, explained Jean-Claude Dujardin, an author of the study and head of molecular parasitology at the ITG. "It aims at improving surveillance at the regional level."

Researchers are working to simplify the test for field application, said Narayan Raj Bhattarai, laboratory coordinator at the B.P. Koirala Insitute of Health Sciences in Dharan, Nepal.

Bhattarai expected that, "by the end of the year this test will be available in all kala-azar endemic regions."

Link to abstract in the Journal of Infectious Diseases:

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