'Guppy deployment' debunked as weapon against Zika, dengue
UVic researcher says guppies ineffective against Zika and dengue, damaging to ecosystems
A small but mighty warrior that has being enlisted in the fight against mosquito-borne illnesses including Zika and dengue might not be as effective as originally hoped.
Guppies — typically found in aquariums — were released into waterways and puddles on the theory that they reduce disease risk by devouring mosquito larvae that are the carriers.
But a University of Victoria researcher told On the Island host Gregor Craigie. that "guppy deployment" does more damage to native ecosystems than to the mosquito population.
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"Unfortunately, guppies don't eat mosquitoes unless they have no other food source," biologist Rana El-Sabaawi said. "Releasing them into streams and ditches isn't going to help."
El-Sabaawi, an assistant professor at the University of Victoria, is co-author of a paper on the negative consequences of releasing guppies into Zika- and dengue-infected areas.
El-Sabaawi said the method is not only ineffective but also causes severe ecological damage.
She said a particular concern was two large-scale guppy deployments in recent years.
One was a response to dengue infection in Pakistan in 2013. The other was in Brazil in 2015 in response to the spread of the Zika virus, which has been associated with the birth of thousands of Brazilian babies with abnormally small heads.
El-Sabaawi said researchers found guppies ate mosquito larvae if it was the only food available.
"But when you introduce them into a water body that has more than one different food source, it's not really clear that they go after the mosquitoes," she said.
"And we have a lot of evidence from our work that they actually prefer other food sources."
Furthermore the ability of guppies to reproduce quickly causes problems for native species, she said.
Small but highly invasive
"They're quite small but highly invasive," she said because a single pregnant female can establish a guppy population.
"We've seen them reduce native fish species by quite a lot," she said. "They compete with them for food. They actually spread diseases and parasites to native fish and they change the way the ecosystem behaves."
The use of native fish species instead of guppies has been problematic as well where it has been tried in Brazil, she said, because it depleted fish populations in local lakes and rivers.
El-Sabaawi said a better strategy is to invest in proven disease-control strategies such as window screens and covering open water tanks.
To hear the full interview on CBC Radio One's On the Island program go to: 'Guppy deployment' debunked as weapon against zika, dengue