Algae may be the solution to wipe out Zika virus

[USA] If there is anyone sympathetic to the mosquito’s cause, a conversation with David Herrin would probably be lively or very short.

The University of Texas researcher wants to contribute to humanity’s effort to kill off vast numbers of the blood-sucking pests. He’s among the many scientists who have few qualms about looking for creative ways to exterminate mosquitoes, which are drawing international attention because of their role in spreading the Zika virus. Herrin’s contribution is a type of algae that is safe for general use but modified to rip a mosquito’s gut apart.

“We can’t kill them all,” he said. “But the idea is to try and knock them back by 80 percent or 90 percent. This is an issue of disease transmission.”

Generally speaking, it is not good to kill off a species. Many play an important role in an ecosystem and sometimes prove that nature can yield miracles. Few would claim to understand how all the strands in the web of life are interwoven.

Mosquitoes evoke a different response, even among experts. Pushing mosquito control to its limits would have minimal, if any, environmental downside, say scientists with expertise in the mosquito’s ecological role — scientists who answer the question of the pros and cons so thoroughly and quickly as to make it appear rhetorical. Around the world, numerous efforts, including genetic modification, are underway to eradicate Aedes aegypti, the mosquito species that spreads Zika.

A municipal health agent sprayed insecticide to combat Aedes aegypti mosquitoes
A municipal health agent sprayed insecticide to combat Aedes aegypti mosquitoes, which transmit diseases like the Zika virus, in Recife, Brazil, Feb. 16, 2016. In the wake of the Zika epidemic, hundreds of families in northeastern Brazil are facing the prospect of raising a disabled child in poverty. (Mauricio Lima/The New York Times)

Texas is at particular risk for the spread of Zika this spring. Health officials have already confirmed more than a dozen cases in the state, including two in Travis County. Warm temperatures naturally lead to the spawning of those biting, buzzing, barbecue-ruining mosquitoes. If the El Niño weather pattern produces a wetter-than-normal spring, as many meteorologists expect, that could lead to more pools of fetid standing water in which mosquitoes breed.

“It’s only a matter of time before Zika virus is locally transmitted here by mosquitoes,” John Hellerstedt, the state health department commissioner, recently told the American-Statesman.

Zika is spread mainly through Aedes aegypti, and it is thought to also be spread through another type of mosquito, Aedes albopictus. Both are invasive species introduced to the Western Hemisphere because of human activity, said Gabriel Hamer, a Texas A&M University entomology professor. Their presence in Texas isn’t natural, he said.

“The ‘ecosystem service’ these two species provide is probably close to zero,” he said, “and definitely not at all important given that these two species are responsible for a huge global health burden.”

That is the consensusamong experts.

Zika-infected people can develop fever, aches, rashes and red eyes. But a main concern is the potential threat to pregnant women: Many mothers who contracted the virus during pregnancy have had babies born with microcephaly, a condition in which the head is much smaller than in typical babies and the brain is less developed. In addition, health authorities are investigating a link between Zika and a nerve illness called Guillain-Barré syndrome that can cause paralysis.

With Zika linked to such human suffering, and other diseases linked to the animal that spreads it, Herrin wants to kill mosquitoes by poisoning them.

The professor’s work, which was funded by a $150,000 National Institutes of Health Small Business Technology Transfer grant, was originally intended to counter West Nile virus, another mosquito-borne disease.

Herrin wants to use algae as a substitute for some of the chemicals used to control mosquito populations. He is combining algae — good for use in the ponds in which mosquito larvae grow — with a bacterium that attacks mosquitoes. The bacterium has specific tastes: It attacks only mosquitoes and blackflies, targeting the gut, Herrin said. He thinks he can even modify the algae to be dangerous only to the kind of mosquitoes that carry Zika.

Bats and dragonflies do eat mosquitoes, Herrin said. But they have enough other food sources that “eliminating (mosquitoes) would not make a difference … even the mosquito fish eats other things,” he said.

The algae won’t be ready for use this spring. Herrin’s company, Pond Life Technologies, is seeking another round of federal grants, which would be followed by safety trials with other animals. Even under the most optimistic scenarios, it won’t eliminate all mosquitoes. A mosquito population can restore itself in 10 days, he said, and a good rain will foster more habitat than people could ever account for.

Mosquitoes are resilient critters, Hamer said.

“Eliminating mosquitoes is not even realistic; there are about 85 species that live in Texas alone,” he said. “But targeted control aiming to suppress or even eliminate a particular species, such as Aedes aegypti or Aedes albopictus, would be great.”

 

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