Just a Matter of Time

Jan 12, 2015

It was just a matter of time.

It was just a matter of time before the so-called "super mosquito" surfaced, resulting in the failure of insecticide-treated nets to provide meaningful control from malaria in some localities in Africa.

"It's  a ‘super' with respect to its ability to survive exposure to the insecticides on treated bed nets,” said medical entomologist Gregory Lanzaro, director of the Vector Genetics Laboratory at the School of Veterinary Medicine, University of California, Davis, who led the research team.

He and his colleagues recently discovered that interbreeding of two malaria mosquito species in the West African country of Mali, has resulted in “a super mosquito” hybrid that's resistant to insecticide-treated bed nets. 

Anopheles gambiae, a major malaria vector, is interbreeding with isolated pockets of another malaria mosquito, A coluzzii.

The research, published in “The Proceedings of the National Academy of Sciences, “provides convincing evidence indicating that a man-made change in the environment--the introduction of insecticides--has altered the evolutionary relationship between two species, in this case a breakdown in the reproductive isolation that separates them,” said Lanzaro, a professor in the Department of Pathology, Microbiology and Immunology in the School of Veterinary Medicine.

“What we provide in this new paper is an example of one unusual mechanism that has promoted the rapid evolution of insecticide resistance in one of the major malaria mosquito species.”

Lanzaro and his "blood brother" medical entomologist Anthony Cornel of the Department of Entomology and Nematology have been researching mosquitoes in Mali since 1991.

Lanzaro called the need to develop new and effective malaria vector control strategies  "urgent.” 

Said Lanzaro: "A number of new strategies are in development, including new insecticides, biological agents--including mosquito killing bacteria and fungi--and genetic manipulation of mosquitoes aimed at either killing them or altering their ability to transmit the malaria parasite. These efforts need to be stepped up.” 

The paper is titled “Adaptive Introgression in an African Malaria Mosquito Coincident with the Increase Usage of Insecticide-Treated Bed Nets.” First author is Laura Norris, then a postdoctoral scholar in the UC Davis Department of Entomology and Nematology who was supported by a National Institutes of Health T32 training grant awarded to Lanzaro. Norris has since accepted a position with the President's Malaria Initiative in Washington, D.C.

In addition to Lanzaro and Cornel, the co-authors include Yoosook Lee and Travis Collier of the Vector Genetics Lab and the Department of Pathology, Microbiology and Immunology; and Abdrahamane Fofana of the Malaria Research and Training Center at the University of Bamako, Mali. Three grants from the National Institutes of Health funded the research.