Mosquitoes quickly develop resistance to insecticide-treated nets, raising alarm that the method of malaria prevention is not effective, a study from Senegal found.  Researchers who studied malaria infections there found that Anopheles gambiae mosquitoes, the species responsible for malaria in Africa, are growing resistant to a common type of insecticide. 

The implication here is that the disease may rebound, the study said.  These findings are of great concern, researchers from the Development Research Institute in Dakar wrote Thursday in The Lancet Infectious Diseases journal.

Massive efforts have done little to deter malaria, despite widespread use of insecticides, indoor spraying, and bednets combined with drugs.  Malaria still kills an alarming 800,000 people each year.  Most of its victims are babies and young children in sub-Saharan Africa. 

Jean-Francois Trape, the study's leader, said that this could have serious, fatal repercussions for control strategies as there are very few cheap and effective methods. 

Trape's team evaluated the effect of using malaria drugs called artemisinin-combination therapies (ACTs) as treatment for malaria, combined with deltamethrin, one of the main insecticides used to control malaria in Africa.   

The study evaluated data on malaria and mosquitoes in the village of Dielmo in Senegal gathered one and a half years before the measures were introduced and again two and a half years after.

The study discovered that two years after bednets were distributed, incidences of malaria decreased significantly.  However, between September and December 2010, incidences increased in adults and older children to unprecedented levels.   

Thirty-seven percent of the village's mosquitoes were found to be resistant to deltamethrin in 2010, and increased from eight percent in 2007 to 48 percent in 2010 due to a genetic mutation that is a catalyst for resistance. 

Strategies to address the problem of insecticide resistance and to mitigate its effects must be urgently defined and implemented, researchers wrote.