Featured Research

from universities, journals, and other organizations

Mosquito nets do not work everytime, researchers find

Date:
January 10, 2011
Source:
Institute of Tropical Medicine Antwerp
Summary:
Long-lasting insecticidal nets have yielded an important breakthrough in malaria prevention, but this does not automatically mean they always work against diseases transmitted by insect bites. Against the transmission of kala-azar disease in India and Nepal, they did not have an effect, researchers have found.

Long-lasting insecticidal nets have yielded an important breakthrough in malaria prevention, but this does not automatically mean they always work against diseases transmitted by insect bites. Against the transmission of kala-azar disease in India and Nepal, they did not have an effect. This was reported by an international group of researchers, led by Marleen Boelaert of the Institute of Tropical Medicine Antwerp, in the British Medical Journal.

Kala-azar, or visceral leishmaniasis in doctor's speak, affects half a million people annually. The Leshmania parasite, in fact a group of related parasites, is transmitted by sand flies. The parasite destroys your blood cells, leading to an enlarged spleen, inflammation and progressive wasting. If left untreated, the outcome is fatal.

Until now, in India and Nepal sand flies are controlled by indoor spraying of DDT or other insecticides; some families use classical mosquito nets, which are not treated with long-lasting insecticides. Spraying happens local and irregular, which means at any moment sufficient sand flies and prey remain to continue the disease. As an alternative for DDT, a large scale campaign was proposed, providing everyone in a region with a mosquito net treated with insecticide that remains active for several years.

Such a campaign needs a large amount of money and effort, so the researchers of the Institute of Tropical medicine, together with colleagues from England, Switzerland, India and Nepal, first checked if it made sense. The prospects were good: in Sudan the approach had worked -- but there the disease was transmitted by a different sand fly. And in Syria and Iran, the treated nets had helped against cutaneous leishmaniasis, caused by other species of the genus Leishmania. It was also known that the sand fly transmitting the disease on the Indian continent, often bites indoor and mostly at night. So sleaping under a net had to make sense.

However. The scientists followed twenty thousand people during two years, in 26 hamlets with a high incidence of visceral leishmaniasis, in India and Nepal. The hamlets were divided into pairs, which resembled each other as much as possible. Tossing a coin decided which hamlet continued as usual, and which would receive treated nets on top. All communities had agreed with this procedure beforehand. During the period of the study, about half the villages were sprayed under the routine national control program.

In the hamlets with extra mosquito nets the sand flies indoor were reduced by a quarter, but the number of infections was not significantly lower than in the control hamlets. Neither did the number of cases of leishmaniasis (luckily, not every infection leads to disease). To be precise: the disease risk went down with 1%, which could be just as well due to chance. Yet in the campaign-villages 90% of people slept under their nets for more than 80% of the nights, while in the control hamlets only 30% of people slept regularly under an (untreated) net.

In contrast, the number of malaria cases did significantly go down in the villages with the extra nets.

The most likely explanation is that sand flies bite more often outdoors than was previously assumed, where nets are not readily useable.

This study, the first on such a scale, shows that medicine shouldn't generalise its results too fast, and that it's always a good idea to do field research before launching grand scale campaigns. And that, for such a campaign against kala-azar to have effect, research into the behaviour of sand flies is urgently needed.


Story Source:

The above story is based on materials provided by Institute of Tropical Medicine Antwerp. Note: Materials may be edited for content and length.


Journal Reference:

  1. A. Picado, S. P. Singh, S. Rijal, S. Sundar, B. Ostyn, F. Chappuis, S. Uranw, K. Gidwani, B. Khanal, M. Rai, I. S. Paudel, M. L. Das, R. Kumar, P. Srivastava, J. C. Dujardin, V. Vanlerberghe, E. W. Andersen, C. R. Davies, M. Boelaert. Longlasting insecticidal nets for prevention of Leishmania donovani infection in India and Nepal: paired cluster randomised trial. BMJ, 2010; 341 (dec29 1): c6760 DOI: 10.1136/bmj.c6760

Cite This Page:

Institute of Tropical Medicine Antwerp. "Mosquito nets do not work everytime, researchers find." ScienceDaily. ScienceDaily, 10 January 2011. <www.sciencedaily.com/releases/2011/01/110105071141.htm>.
Institute of Tropical Medicine Antwerp. (2011, January 10). Mosquito nets do not work everytime, researchers find. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2011/01/110105071141.htm
Institute of Tropical Medicine Antwerp. "Mosquito nets do not work everytime, researchers find." ScienceDaily. www.sciencedaily.com/releases/2011/01/110105071141.htm (accessed September 19, 2014).

Share This



More Plants & Animals News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Chimp Violence Study Renews Debate On Why They Kill

Chimp Violence Study Renews Debate On Why They Kill

Newsy (Sep. 17, 2014) The study weighs in on a debate over whether chimps are naturally violent or become that way due to human interference in the environment. Video provided by Newsy
Powered by NewsLook.com
Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins