Treated bednets ‘give little additional protection against leishmaniasis’

Bednets do not alwys protect against sandflies Copyright: Flickr/AJC1

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[HYDERABAD] Insecticide-sprayed bednets do not provide significant protection against the sandfly that transmits leishmaniasis, a neglected, re-emerging disease that kills thousands of people in tropical countries each year, according to a new study.

The study, published last month (29 December) by the British Medical Journal (BMJ), contradicts the findings of a European Commission-funded project, published in PLoS Neglected Tropical Diseases in February 2010. The project had found that treated bednets stop the spread of the disease.

The London School of Hygiene and Tropical Medicine and Médicins Sans Frontières in Sudan, reported in the March 2007 issue of Tropical Medicine and International Health that new cases had decreased by almost half through using treated bednets.

The latest study, led by Marleen Boelaert, an epidemiologist at the Institute of Tropical Medicine, Antwerp, was conducted on more than 20,000 people across 26 villages in northern and eastern India and Nepal. It examined whether bednets treated with the insecticide deltamethrin, combined with conventional spraying with DDT, reduced the incidence of ‘visceral leishmaniasis’, also known as kala-azar, which affects the liver and spleen.

When compared with a control population in villages where no such bednets had been used, reduction in the disease was just one per cent.

The disparity in findings indicates that the behaviour of the sandfly may be different across regions, said the report in the BMJ .

Strategies that work in one region may fail in others, Rentala Madhubala, a professor at the department of life sciences at Jawaharlal Nehru University, New Delhi, told SciDev.Net.

"In India, the sandfly species seem to be active mostly outdoors and during the day, so nets do not really offer protection," Madhubala said. "Better housing, improved sanitation and a community-based approach, focusing on education and awareness about the infection, are key to helping control the vector."  

Currently available drugs are expensive and some are highly toxic. Poor compliance with treatment schedules also leads to drug resistance, she noted.

Nearly 500,000 new cases of visceral leishmaniasis are reported worldwide each year, leading to 50,000 deaths.

The Indian Leishmania Research Society says that the Indian subcontinent accounts for nearly 67 per cent of total cases of infection with leishmaniasis, a parasitic infection second only to malaria as a killer, in some areas.

Link to full article in the British Medical Journal