After recently mapping all the DNA, or genome, of the mosquito that spreads yellow and dengue fever, scientists were surprised to find it is more complex than the genome of the mosquito that carries malaria. Scientists plan to use this information to help them battle disease.
Researchers published the genome yesterday for the mosquito, Aedes aegypti, which spreads disease in tropical and sub-tropical locales worldwide as it feeds on human blood. The mosquito's genome could guide researchers' efforts to develop new insecticides or to create genetically engineered varieties of this mosquito that are either unable or less able to transmit the viruses that cause yellow fever and dengue fever.
Only a few insect genomes have been completely mapped so far, including one other mosquito species, Anopheles gambiae, which was published in 2002. This other species carries the malaria parasite. Even there are approximately 3,500 mosquito species worldwide, these two cause the most human misery.
The researchers discovered that the genome for Aedes is about five times larger than the one for Anopheles. Even though both species have roughly 16,000 genes, Aedes is loaded up with extra DNA, sometimes referred to as "junk DNA", whose function is unknown.
Yellow fever is an acute viral disease that kills about 30,000 people annually. It is a common affliction in West and Central Africa and in parts of South America, where it has sometimes been the source of deadly epidemics. Even though a vaccine has been available for decades, the number of people infected has increased in the past 20 years, according to the World Health Organization.
Dengue fever, sometimes known as breakbone fever because of the severe pain it causes, is caused by four closely related viruses. It occurs in about 100 countries in tropical areas of the world and kills about 25,000 people annually. There is no vaccine.
"These are huge global health issues," said Vishvanath Nene of the J. Craig Venter Institute in Rockville, Maryland, who led the study.
Mosquitoes first appeared 170 million years ago when the dinosaurs still roamed the planet. The yellow fever and malaria mosquitoes are ancient; they diverged evolutionarily from one another about 150 million years ago.
"They both are very robust, very fit mosquitoes. And they love to feed on human blood," observed one of the researchers, David Severson of the University of Notre Dame in Indiana.
Aedes originated in Africa. It is a small, dark mosquito with white markings and banded legs. Centuries ago, people unwittingly spread this mosquito to tropical and subtropical regions worldwide when it hitchhiked along with them on transoceanic voyages. These mosquitoes commonly bite humans just after dawn and prior to sunset.
In contrast to Aedes, many Anopheles mosquitoes can live in colder latitudes. They are active at dawn and dusk, when they do most of their biting.
"Their physical appearance is quite different. And their behavior is quite different. And as we see with their genome architecture, it's also very, very different," Severson noted.
Source
Reuters (quotes)
