Featured Research

from universities, journals, and other organizations

Scientists determine alternative insecticide dramatically reduces malaria transmission

Date:
October 10, 2011
Source:
American Society of Tropical Medicine and Hygiene
Summary:
Indoor spraying with the insecticide bendiocarb has dramatically decreased malaria transmission in many parts of Benin, new evidence that insecticides remain a potent weapon for fighting malaria in Africa despite the rapid rise of resistance to an entire class of mosquito-killing compounds, according to a new study.

Indoor spraying with the insecticide bendiocarb has dramatically decreased malaria transmission in many parts of Benin, new evidence that insecticides remain a potent weapon for fighting malaria in Africa despite the rapid rise of resistance to an entire class of mosquito-killing compounds, according to a study published October 5 in the October edition of The American Journal of Tropical Medicine and Hygiene.

Scientists with Benin's Entomologic Research Center in Cotonou evaluated the effects of two applications of bendiocarb in homes throughout the West African country over an eight-month period in 2009. They found that after "indoor residual spraying" or IRS, which involves applying insecticide on walls where mosquitoes are likely to land, none of the 350,000 household members living in the treated homes "received infected bites" from the malaria-carrying mosquito Anopheles gambiae.

Moreover, none of the mosquitoes collected from the treated homes tested positive for the Plasmodium falciparum -- the world's most deadly malaria parasite. The absence of infected bites and parasites was seen as evidence that malaria transmission had fallen precipitously in an area where mosquitoes have developed resistance to permethrin and other members of a popular class of insecticides known as pyrethroids.

"Our success in drastically reducing malaria transmission by spraying homes with bendiocarb, which is not a pyrethroid, is very important because pyrethroid-resistance is emerging not just in Benin but also in Kenya, Niger, Nigeria, Mali, Cameroon and many other African countries," Gil Germain Padonou, MSc, a medical entomologist, who co-authored the study. "Our results should provide reassurance that despite the rise in pyrethroid resistance, indoor spraying can continue to play a vital role in reducing the incredible burden of malaria across Africa."

The successful lifecycle of the malaria parasite depends on constantly moving from mosquitoes to humans and from humans back to the mosquito. Indoor spraying and bednets disrupt this lifecycle by broadly preventing mosquitoes from an opportunity to feed on infected blood and thus obtain and transmit the malaria parasite. The researchers believe that where there was indoor spraying, malaria transmission likely continued at a very low level difficult to detect. They conclude that it would have required analyzing "thousands of mosquitoes to find any positive for malaria parasites."

While the study did not formally collect data on how the spraying affected malaria illnesses and deaths, Padonou said there are anecdotal reports from doctors in the region of a "significant reduction in malaria cases" in their clinics following the IRS campaign. Virtually all of Benin's 9.3 million people are at risk of malaria infections. Each year, malaria sickens more than a million people in Benin and kills thousands. Malaria accounts for about a quarter of all hospital admissions in Benin and a third of the deaths in children under five.

Bendiocarb has been deployed in the fight against malaria despite the fact that it has been voluntarily withdrawn from the U.S. market due to safety concerns. The World Health Organization has approved its use -- with strict safety protocols -- for indoor spraying programs to combat malaria. Padonou said investigators in Benin monitored for both human and environmental exposures and found no evidence of any adverse events.

The indoor spraying campaign in Benin was conducted by the country's National Malaria Control Program, with support from the U.S. through the President's Malaria Initiative. This is part of a broad effort to find alternatives to pyrethroids, the mainstay of public health campaigns against malaria, chiefly through the distribution of insecticide-treated bednets (ITNs) and indoor spraying campaigns. Malaria experts point to wider use of both interventions -- coupled with greater access to malaria medicines and diagnostics -- as a key reason why malaria deaths in Africa have dropped by more than a third over the last decade, which represents about 1.1 million lives saved.

However, there are fears that insecticide resistance could stall or even reverse this progress.

"Insecticide resistance has been lurking for several years now as a spoiler for the incredible success we have seen in fighting malaria, particularly in Africa, where most of the world's malaria deaths occur," said Peter J. Hotez, MD, PhD, president of the American Society of Tropical Medicine and Hygiene. "We need to intensify support for efforts to develop and test new insecticides and seek better strategies for using them, such as rotating among several different compounds that make it harder for mosquitoes to become resistant. Keeping a constant flow of new products and technologies in pipeline requires funding. If we backpedal now on research and development, we could lose not only the chance to eradicate malaria, but there is also the very real potential we could see an uptick in absolutely preventable malaria diseases, especially among children. This would be unacceptable by any metric."

Padonou and his colleagues worked with the Malaria Control Program to evaluate the capacity of both indoor spraying with bendiocarb and much wider use of ITNs (which continue to be treated with pyrethroids) to interrupt malaria transmission.

Indoor spraying was tested in homes in what is known as the plateau region of Benin, which alternates between wet and dry seasons. But in swampy, frequently flooded areas of Benin, there was concern that indoor spraying with any malaria-killing insecticides could produce toxic runoff into local waterways. Therefore, public health officials opted for increased distribution of ITNs as the primary tool for reducing transmission

The study reports that both indoor spraying and treated bednets demonstrated a capacity to significantly decrease malaria transmission. For the areas that received indoor spraying, infected bites declined by 94 percent overall during the eight-month study, though in some villages scientists believe infected bites stopped altogether. No one living in a treated home received an infected bite. Bites from infectious mosquitoes also declined substantially in areas where there was increased distribution of ITNs, though the drop was about 5 percent less than what was achieved via indoor spraying.

In contrast, in an area of Benin that received neither indoor spraying nor increased access to treated nets, each resident received an average of 120 infected bites over the same period.

"The best way to control malaria would be to use both indoor spraying and treated bednets, at the same time," Padonou said. Bednets protect people from mosquitoes that may first land and "feed" on a human before lighting on a treated surface and indoor spraying kills mosquitoes en masse offering protection even when you are not sleeping. "Such an approach is too expensive for most national malaria programs and should be reserved for areas that have a particularly high level of malaria."

Researchers are now on the lookout for bendiocarb resistance. Padonou said there is early evidence of resistance in a mosquito population in neighboring Burkina Faso, demonstrating a need to develop multiple alternatives to pyrethroids.


Story Source:

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


Cite This Page:

American Society of Tropical Medicine and Hygiene. "Scientists determine alternative insecticide dramatically reduces malaria transmission." ScienceDaily. ScienceDaily, 10 October 2011. <www.sciencedaily.com/releases/2011/10/111005172635.htm>.
American Society of Tropical Medicine and Hygiene. (2011, October 10). Scientists determine alternative insecticide dramatically reduces malaria transmission. ScienceDaily. Retrieved September 3, 2014 from www.sciencedaily.com/releases/2011/10/111005172635.htm
American Society of Tropical Medicine and Hygiene. "Scientists determine alternative insecticide dramatically reduces malaria transmission." ScienceDaily. www.sciencedaily.com/releases/2011/10/111005172635.htm (accessed September 3, 2014).

Share This



More Health & Medicine News

Wednesday, September 3, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Snack Attack: Study Says Action Movies Make You Snack More

Snack Attack: Study Says Action Movies Make You Snack More

Newsy (Sep. 2, 2014) You're more likely to gain weight while watching action flicks than you are watching other types of programming, says a new study published in JAMA. Video provided by Newsy
Powered by NewsLook.com
U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

U.N. Says Ebola Travel Restrictions Will Cause Food Shortage

Newsy (Sep. 2, 2014) The U.N. says the problem is two-fold — quarantine zones and travel restrictions are limiting the movement of both people and food. Video provided by Newsy
Powered by NewsLook.com
Doctors Fear They're Losing Battle Against Ebola

Doctors Fear They're Losing Battle Against Ebola

AP (Sep. 2, 2014) As a third American missionary is confirmed to have contracted Ebola in Liberia, doctors on the ground in West Africa fear they're losing the battle against the outbreak. (Sept. 2) Video provided by AP
Powered by NewsLook.com
Tech Giants Bet on 3D Headsets for Gaming, Healthcare

Tech Giants Bet on 3D Headsets for Gaming, Healthcare

AFP (Sep. 2, 2014) When Facebook acquired the virtual reality hardware developer Oculus VR in March for $2 billion, CEO Mark Zuckerberg hailed the firm's technology as "a new communication platform." Duration: 02:24 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