Various strategies are being used to study methods of controlling the mosquito-borne Zika virus’ spread in Latin America.
Laura Harrington, professor and chair of Cornell University’s Department of Entomology, discussed a new Cornell study on mating induced changes in genes expression to identify targets to fight mosquito-borne diseases at a March 15 briefing at the National Press Club in Washington, D.C.
The Aedes aegypti mosquito is the primary transmitter of Zika virus and lives in close proximity to human populations, she said, noting most people who contract Zika don’t have symptoms. Other diseases spread by Aedes aegypti include dengue fever, chikungunya and the yellow fever virus.
Scientists are studying genetic changes that occur after Aedes aegypti mosquitoes mate as a means of targeting important aspects of their physiology and behavior, and, ultimately, eliminating their ability to reproduce. Harrington was joined by Alaka Basu, Cornell professor of development sociology and senior fellow for public health at the United Nations Foundation.
There is a critical need to develop new mosquito control tools rather than using the same old strategies that often can have minimal success, especially for a mosquito like Aedes aegypti, Harrington said. She went on to explain the reasons why Aedes aegypti is so difficult to control, including the fact that it is a painless biter and frequent human blood feeder, lives in very close association with humans and can breed in small and often hidden water filled containers. It can also develop high levels of resistance to insecticides.
A mosquito that picks up any of these viruses is infected for life and can go on to infect people, though the mosquito tends not to travel far (often staying within 100-meters from the homes and man-made containers where it “grew up”), she told reporters.
Instead of conventional insecticide control, an alternate way to control mosquitoes spreading the virus is by interfering with its ability to reproduce. That is why the Cornell team is focusing on this strategy.
Basu cited social and cultural factors at play in combatting the disease. While questions remain about the epidemiology of the Zika virus, it is known that storing drinking water – a common practice in poorer areas – helps facilitate populations of mosquitoes that carry the virus, she said. One solution is to remove containers that people use for storage.
Water sources and mosquitoes are important in public health. Having improved access to safe water also can reduce instances of malaria and dengue fever.
Standard Aedes aegypti control efforts treat containers of water with pesticides to kill larvae, though it is hard to find and treat all containers and pesticides need to be used that are safe for drinking, Harrington said. During epidemics insecticide spray is used with micro-fine droplets that theoretically float through the air and come in contact with mosquitoes, but it can be hard to reach mosquitoes in protected locations such as indoor resting sites.
Another concern is for women who are or could become pregnant. Human-to-human transmission beyond mosquitoes, such as could be sexually transmitted, said Basu, who specializes in reproductive health and child mortality.
“We don’t know if, as was the case with HIV/AIDS, there’s also a risk of transmission through blood transfusion,” she said.
Levels of contraception use are higher in Latin America, even with the prevalence of Catholicism there, than in Asia and Africa, she said. The exceptions in Latin America are contraceptive use among poor, indigenous groups and young women.
John Seidenberg is a freelance writer in the Washington, D.C. area.