Mosquito-Borne Diseases to Be Fought by Modified Mosquitoes in Florida

The fight against mosquito-borne diseases and growing insecticide resistance may have gained a new weapon—the mosquitoes themselves. That is, if the FDA approves modifications to their genome.

Painful viral infections like dengue fever and chikungunya—which causes such severe contortions that the name translates to “that which bends over”—are both transmitted by mosquitoes. Last year, the first cases of chikungunya transmitted in the Americas were reported in the Caribbean, and dengue epidemics have been occurring in Puerto Rico since the 1960s.

Original Title: Aa_FC3_11a.jpg
A female Aedes ageypti mosquito lands on a human host for a blood meal. Aedes aegypti mosquitoes transmit the viruses that cause dengue fever and chikungunya

Beyond managing the pain, fevers, and other symptoms,there are no treatments or vaccines for either dengue or chikungunya, and insecticide use is increasingly unsuccessful at combating the spread of these diseases; Aedes aegypti mosquitoes, the species that carry both diseases, are now able to evade four of the six insecticides leveled against them, according to the Associated Press.

Now, British biotech firm Oxitec is proposing to kill mosquitoes in the Florida Keys from the inside, out. They have developed a strain of genetically modified mosquitoes that possess a mélange of genes from the herpes simplex virus, E. coli bacteria, cabbage, and coral. When the mutated males breed with wild-type females in the general mosquito population, the larvae that result die, reducing the number of disease-transmitting adults in the following generation.

In tests conducted outside of the U.S., Oxitec’s strategy has diminished mosquito populations. One peer-reviewed study published in Nature Biotechnology demonstrated that mating a wild-type female with a modified male mosquito in the lab killed over 96% of the offspring. When 3.3 million modified mosquitoes were released in the Cayman Islands, they reduced mosquito populations by 80% compared to areas with no genetically modified mosquitoes, according to a commentary published in 2012 which wasn’t subject to peer review.

Although at the time Oxitec apparently ran into trouble for not obtaining the necessary consent for these trials, Nidhi Subbaraman reported for Nature Biotechnology News that “William Petrie, director of the MRCU in the Cayman Islands, says the sterile transgenic mosquito release technique is head and shoulders above the population control methods currently in place there.”

Support for genetically modified mosquitoes being released in Florida though, remains tenuous. “I think the science is fine, they definitely can kill mosquitoes, but the GMO issue still sticks as something of a thorny issue for the general public,” Phil Lounibos—who studies mosquito control at the Florida Medical Entomology Laboratory—told Jennifer Kay of the Associated Press.

This is not the first proposal to prevent the spread of deadly mosquito-borne diseases by genetically modifying the vectors. In July 2014, Tim De Chant and Eleanor Nelsen reported for NOVA Next that the newly developed CRISPR-Cas9 gene editing system could be used to drive killer mutations through populations of mosquitoes—wiping them out. However, George Church, a professor of genetics at Harvard Medical School and co-author of the proposal, urged caution.

“I think we need to be cautious with all new technologies, especially all new technologies that are messing with nature in some way or another. But there’s also a risk of doing nothing,” Church told De Chant and Nelsen. “We have a population of 7 billion people. You have to deal with the environmental consequences of that.”