To reduce the number of disease-spreading mosquitoes, the Colombian city of Cali is planning a counter-intuitive strategy: releasing more mosquitoes. The science-based approach comes from U.K. biotechnology company Oxitec Ltd., which has developed a genetically modified male version of the Aedes aegypti species that mate with local females to produce offspring that will “inherit a self-limiting gene that causes them to die before reaching functional adulthood,” according to the company.
Only female Aedes aegypti bite humans — in the process transmitting dangerous diseases including Zika, dengue, chikungunya, and yellow fever — while the modified “Friendly Aedes” males should have no adverse health effects and suppress the mosquito population.
Cali plans to deploy the solution in its Comuna 16 neighborhood that is home to around 100,000 residents. This “initial project,” according to Oxitec, is expected to begin after the necessary permits and licenses are finalized.
“This single urban-dwelling mosquito species has been responsible for the vast majority of dangerous viruses transmitted to our residents leading to a variety of health disorders,” said Alex Durán, health secretary of Cali. “We are enthusiastic about the adoption of such an innovative solution and are excited to get the program underway as expeditiously as possible.”
Results from a similar rollout in Piracicaba, Brazil, showed an 81% suppression rate in the local mosquito population, according to Oxitec, which got its start in 2002 through Oxford University Innovation and was bought for $160 million USD in 2015 by U.S.-based Intrexon Corp.
Other trials have taken place in Panama, the Cayman Islands and Brazil, where the high-profile Zika outbreak in 2016 had devastating health effects, including microcephaly-related birth defects, for unborn babies and caused many people to cancel plans to attend the Olympics in Rio. Colombia has suffered through major outbreaks of both Zika and chikungunya in recent years on top of the long-standing instances of dengue and other diseases the persist in the tropical Andean nation. The company says that some trials have shown mosquito population reductions of more than 90%.
In addition to measuring the overall Aedes aeypti population numbers, researchers and officials can individually track the offspring of the “friendly” males through an inherited “fluorescent marker that allows tracking and monitoring at a level never before achieved, making the assessment of effectiveness more accurate,” said the company in a statement. Oxitec notes that its genetically modified males also “die along with their offspring, and therefore do not persist in the environment or leave any ecological footprint.”
Around 20,000 pregnant women in Colombia were confirmed to have contracted Zika during the country’s epidemic in 2015 and 2016. At least 475 cases of microcephaly were recorded in 2016, some four times the historic rate in Colombia, according to a report from the country’s national health department and the U.S. Centers for Disease Control and Prevention.