Scientists attempting to halt Dengue fever have, for the first time, released mosquitoes into the wild that were genetically modified to pass on deadly DNA that kills their offspring. About 19,000 lab-altered insects were cast loose on 25 acre of land on Grand Cayman Island in 2009, according to a report yesterday in the journal Nature Biotechnology. Later tests showed they made up about 16 percent of the mosquito population, and that the fatal gene was carried by about 10 percent of larvae. Scientists said the modified insects -- all males -- were about half as successful in mating as normal.
