News Summary

• Medical School researchers have identified a subgroup of mosquito that may be especially detrimental when it comes to the spread of malaria.
• The new subgroup of mosquito lives primarily outdoors -- even after stinging someone indoors.
• The finding may change how people fight the spread of malaria since most current measures focus on protection and eradication of mosquitoes indoors.

Quotes

“The bottom line is that current control measures for malaria are achieving less-than-satisfying levels of impact. it has been known – but not fully appreciated – that mosquitoes that don’t rest indoors can still infect people with this deadly disease," said Kenneth Vernick, Ph.D., principal investigator of the study.

“This research tells us that we may need a new set of tools to help control malaria infected mosquitoes," Riehle said. “We need to develop preventive measures effective against outdoor resting mosquitoes that can be used in conjunction with existing indoor control measures, " said Michelle Riehle, Ph.D., the first-author of the study.

Full Text

MINNEAPOLIS / ST. PAUL (February 3, 2011) – Attempts to control the spread of malaria through eradication of mosquitoes have been largely unsuccessful, and according to new University of Minnesota research there may be a good reason why: current control strategies may not be targeting all of the mosquitoes capable of spreading the disease.

Current and past attempts to control the spread of malaria largely focus on devices such as bed nets, sprays and other toxic agents that target mosquitoes who bite and infect people indoors.

To date, most researchers have primarily used indoor collection methods to see which mosquitoes are most susceptible to transmit malaria. But there is no doubt that the data is incomplete since outdoor resting mosquitoes contribute to malaria transmission, and are not represented during indoor collections.

As a result, University of Minnesota Medical School researchers targeted pools of water where adult mosquitoes go to lay eggs. It proved an ideal sampling site for comprehensive mosquito population monitoring – because the reproduction area is blind to whether the mosquitoes rest indoors or outdoors.

They discovered a newly defined subgroup of the Anopheles gambiae mosquito that does not rest indoors after a blood meal, is numerically abundant, and two-thirds more susceptible to infection by human malaria parasites than the indoor resting subgroup in experimental infection tests.

The study, led by U of M Medical School microbiologists Michelle Riehle, Ph.D., and Kenneth Vernick, Ph.D., is published online today in the journal Science.

“The bottom line is that current control measures for malaria are achieving less-than-satisfying levels of impact,” Vernick said. “It has been known – but not fully appreciated – that mosquitoes that don’t rest indoors can still infect people with this deadly disease.”

Malaria is a mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die. In 2008, an estimated 190 - 311 million cases of malaria occurred worldwide and nearly 1 million of those cases resulted in death, most of them young children in sub-Saharan Africa, according to the Center for Disease Control and Prevention.

Researchers studied the Anopheles gambiae mosquito population over a 400 kilometer region of Burkina Faso, in West Africa. They sampled mosquito larvae from water pools within 1 kilometer of villages or other areas where large groups of people live.

Now, the researchers are working to measure portions of cases attributed to this mosquito are actually transmitted by the new subgroup. Because these mosquitoes rest in unknown locations outside of homes – and adult mosquitoes are difficult to capture – this information is still unknown and may prove difficult to gather.

“This research tells us that we may need a new set of tools to help control malaria infected mosquitoes," Riehle said. “We need to develop preventive measures effective against outdoor resting mosquitoes that can be used in conjunction with existing indoor control measures.”

The study was funded by the National Institutes of Health. Collaborators include Wamdaogo Guelbeogo, Awa Gneme and N’Fale Sagnon of the Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso; Karin Eiglmeier, Inge Holm, Emmanuel Bischoff and Thierry Garnier of the Unit of Insect Vector Genetics and Genomics, Department of Parasitology and Mycololgy, Institut Pasteur, Paris, France; Xuanzhong Li and Kyriacos Markianos of the Program in Genetics, Children’s Hospital Boston, Harvard Medical School and Greg Snyder, Department of Microbiology, University of Minnesota.