Nora Besansky, O’Hara Professor of Biological Sciences at the University of Notre Dame and a member of the University’s Eck Institute for Global Health, has led an international team of scientists in sequencing the genomes of 16 Anopheles mosquito species from around the world.
Anopheles mosquitoes are responsible for transmitting human malaria parasites that cause an estimated 200 million cases and more than 600 thousand deaths each year. However, of the almost 500 different Anopheles species, only a few dozen can carry the parasite and only a handful of species are responsible for the vast majority of transmissions. Besansky and her fellow researchers investigated the genetic differences between the deadly parasite-transmitting species and their harmless (but still annoying) cousins.
Two papers published in Science Express, an electronic publication of selected papers of the prestigious journal Science in advance of print, describe detailed genomic comparisons of these mosquitoes and the deadliest of them all, Anopheles gambiae. These results offer new insights into how these species are related to each other and how the dynamic evolution of their genomes may contribute to their flexibility to adapt to new environments and to seek out human blood. These newly sequenced genomes represent a substantial contribution to the scientific resources that will advance our understanding of the diverse biological characteristics of mosquitoes, and help to eliminate diseases that have a major impact on global public health.
Malaria parasites are transmitted to humans by only a few dozen of the many hundreds of species of Anopheles mosquitoes, and of these, only a handful are highly efficient disease-vectors. Thus, although about half the world’s human population is at risk of malaria, most fatalities occur in sub-Saharan Africa, home of the major vector species, Anopheles gambiae. Variation in the ability of different Anopheles species to transmit malaria – known as “vectorial capacity” – are determined by many factors, including feeding and breeding preferences, as well as their immune responses to infections. Much of our understanding of many such processes derives from the sequencing of the Anopheles gambiae genome in 2002, which was led by Notre Dame researchers and which has since facilitated many large-scale functional studies that have offered numerous insights into how this mosquito became highly specialized in order to live amongst and feed upon humans.
Until now, the lack of such genomic resources for other Anopheles limited comparisons to small-scale studies of individual genes with no genome-wide data to investigate key attributes that impact the mosquito’s ability to transmit parasites. To address these questions, researchers sequenced the genomes of 16 Anopheles species.
“We selected species from Africa, Asia, Europe, and Latin America that represent a range of evolutionary distances from Anopheles gambiae, a variety of ecological conditions, and varying degrees of vectorial capacity,” Besansky said.