WASHINGTON, Feb 3 (Reuters) - Researchers have identified some of the tools that mosquitoes use to smell their human prey and said on Wednesday their findings might help find better repellents or ways to trap and kill the pests.

They found 50 different genes that the mosquito Anopheles gambiae uses to sniff out tasty humans, and characterized how each one responded to different uniquely human odors, including those known to attract mosquitoes.

Their analysis, published in the journal Nature, might greatly improve ways to repel mosquitoes - a field dominated by just a few compounds such as DEET.

Each gene controls a receptor " a molecular doorway that in this case attaches to a molecule of human aroma.

John Carlson of Yale University in New Haven, Connecticut, and colleagues transferred the 50 genes into the nerve cell of a type of fruit fly called Drosophila.

Fruit flies are well understood and don't try to smell out humans, so any mosquito gene that lights up in response to a human smell is likely to be one used by mosquitoes to guide them to their blood meals.

"The results may have implications for the control of malaria, one of the world's most devastating diseases,"Carlson's team wrote.

"Screens for activators and inhibitors of selected receptors may identify compounds that attract mosquitoes into traps, interfere with their navigation, or repel them."

Malaria, caused by a parasite, is spread by female mosquitoes seeking human blood. It kills close to 1 million people every year, mostly children and most of them in Africa, according to the World Health Organization.

Mosquitoes also carry a range of other human ills, including dengue fever, West Nile virus, yellow fever and several viruses that cause encephalitis, an often deadly inflammation of the brain.

In two other studies in the same journal, researchers said they found a special protein called plasmepsin V that the malaria parasite uses to get into human red blood cells, and said blocking this protein could lead to better malaria drugs.