With Zika virus on the rise in parts of South and Central America, experts are seeking new ways to curb the spread of the potentially dangerous virus.
The Zika virus can cause an infection with mild symptoms, but experts are concerned that infections in pregnant women may lead to a condition called microcephaly in their children. Microcephaly affects the brain and severely impacts a child's cognitive development. On Feb. 1, the World Health Organization announced that microcephaly possibly linked to the Zika virus constitutes a public health emergency.
Although not yet developed, a vaccine has the potential to offer widespread protection against the virus for people who come into contact with it. But another possible means of preventing the spread of Zika is to target the mosquito that carries the virus, in hopes of preventing bites — and exposure to the virus — in the first place. One way of doing this would be to use insecticides to eliminate the mosquitoes; however, another technique that is gaining popularity is the use of genetically modified mosquitoes. [Zika Virus FAQs: Top Questions Answered]
By manipulating certain genes in the mosquitoes, scientists can cause the population to crash (or, in other words, die off), said Anthony James, a professor of microbiology and molecular genetics at the University of California, Irvine.
This is the genetic equivalent of an insecticide, James told Live Science.
There are several ways to do this. One option is to insert a lethal gene into the sperm of male mosquitoes that causes their offspring to die before they reach adulthood, James said. Another option is to manipulate the genes in the females so that they can't fly — and therefore don't find mates — and leave no offspring, he said.
Aside from these "population suppression" approaches, scientists are also looking into a method called "population replacement." Using population replacement, scientists would tweak a gene in order to reduce the mosquito's ability to transmit a pathogen, he said.
This technique has been tested in mosquitoes that carry the parasite that causes malaria, James said. However, it's a less popular idea in the fight against a flavivirus such as the Zika virus, because rather than targeting just one flavivirus, a researcher would want to target all of them, which would require sufficient engineering, he said. Other flaviviruses carried by mosquitoes include dengue, yellow fever and chikungunya.
Indeed, with the Zika virus, the population-suppression technique is simpler, James said. By eliminating the mosquitoes that carry flaviviruses, rates of all of these diseases would drop, he said.
Currently, one British company called Oxitec has a strain of Aedes aegypti mosquitoes (one of the species that carry flaviviruses) that can be used to suppress the population using males that carry a lethal gene.
The mosquitoes were designed to reduce the spread of the dengue virus, but because the same mosquitoes carry Zika, they could work for the Zika virus as well, James said.
Field trials of these mosquitoes are currently taking place in Brazil, according to the company.
One potential downside to population suppression is that it could affect "nontarget" populations. In other words, researchers consider whether killing off a population will affect others in the area — for example, those that rely on that species for food.
But this isn't a worry with Aedes aegypti mosquitoes, James said. "It's important to emphasize that [A. aegypti] are an invasive species" in the Western Hemisphere, James said. That means that they are not a natural part of the ecosystem, and eliminating them could potentially have positive effects, as opposed to harming the ecosystem, he said.
There are also concerns about what would happen if the manipulated gene were transferred to another species. One way to avoid this is to manipulate the genes in the male mosquitoes, which do not bite and therefore wouldn't come into contact with other species, James said.